U.S. patent application number 11/567502 was filed with the patent office on 2007-12-13 for impact attenuator system.
Invention is credited to James C. JR. Kennedy, Charles R. Miele, Chuck A. Plaxico, Joseph R. Preston, Jay R. Sayre, Carl J. Serman, Kary L. Valentine, W. Scott Versluis.
Application Number | 20070286675 11/567502 |
Document ID | / |
Family ID | 35809744 |
Filed Date | 2007-12-13 |
United States Patent
Application |
20070286675 |
Kind Code |
A1 |
Kennedy; James C. JR. ; et
al. |
December 13, 2007 |
IMPACT ATTENUATOR SYSTEM
Abstract
An impact attenuator system includes a hyperelastic member that
comprises an energy absorbing material which behaves in a
rate-independent hyperelastic manner so that its permanent set is
minimized and the material can absorb tremendous amounts of impact
energy while remaining fully recoverable.
Inventors: |
Kennedy; James C. JR.;
(Worthington, OH) ; Miele; Charles R.; (Upper
Arlington, OH) ; Plaxico; Chuck A.; (Westerville,
OH) ; Preston; Joseph R.; (Radnor, OH) ;
Sayre; Jay R.; (Gahanna, OH) ; Versluis; W.
Scott; (Dublin, OH) ; Serman; Carl J.;
(Cranberry Twp., PA) ; Valentine; Kary L.; (Mars,
PA) |
Correspondence
Address: |
FROST BROWN TODD, LLC
2200 PNC CENTER
201 E. FIFTH STREET
CINCINNATI
OH
45202
US
|
Family ID: |
35809744 |
Appl. No.: |
11/567502 |
Filed: |
December 6, 2006 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
10991080 |
Nov 17, 2004 |
7168880 |
|
|
11567502 |
Dec 6, 2006 |
|
|
|
Current U.S.
Class: |
404/6 ;
404/10 |
Current CPC
Class: |
E01F 15/146 20130101;
C08G 18/10 20130101; C08G 18/10 20130101; C08G 18/664 20130101 |
Class at
Publication: |
404/006 ;
404/010 |
International
Class: |
E01F 15/00 20060101
E01F015/00 |
Claims
1. An impact attenuator system comprises: at least one first side
beam assembly and at least one opposing, or second, side beam
assembly, the first and second beam assemblies are in opposed
relationship, the first beam assembly having a first, or leading,
end and a second end, and the second beam assembly having a first,
or leading, end and a second end; at least one nose assembly that
is secured to the first end of the first beam assembly and to the
first end of the second beam assembly; each side beam assembly
further including a plurality of side panels, each side panel
having a first end and a second end, wherein the second end of a
first panel overlaps the first end of the adjacent panel whereby
the side panel members are in a nested linear arrangement; each
side panel defining at least one longitudinally extending opening
wherein adjacent slots on adjacent side panels at least partially
overlap; at least one diaphragm panel, wherein the diaphragm panel
is positioned between opposing side panels and is secured to the
opposing side panels by at least one securing mechanism, wherein
the securing mechanism extends from an outer surface of the side
panel through the slot, the securing mechanism being capable of
being longitudinally moved along the slot; at least one bay defined
by the opposing side panels and the diaphragm panels; at least one
hyperelastic member positioned in the at least one bay; and, at
least one anchoring system including at least one cable which is
secured at a first end to a first anchoring mechanism and is
secured at a second end to a second anchoring mechanism.
2. The impact attenuator system of claim 1, wherein the
hyperelastic member comprises an energy absorbing material that
behaves in a rate-independent hyperelastic manner whereby its
permanent set is minimized so that the energy absorbing material
can absorb impact energy while remaining fully recoverable.
3. The impact attenuator system of claim 1, wherein the
hyperelastic member comprises at least one energy absorbing
material has at least the properties of: a Shore A hardness value
of at least about 90, elongation at break ranging from about 500 to
about 700%, and Young's modulus ranging from about 4000 to about
6000 psi; and at least withstands: strain rates of up to at least
about 900-1000s.sup.-1, and tensile stresses ranging from at least
about 4000 to at least about 7000 psi.
4. The impact attenuator system of claim 3, wherein the
hyperelastic material behaves in a hyperelastic manner under
dynamic loadings of high strain rates of up to at least about
900-1000s.sup.-1 and has non-linear elastic responses in energy
absorbing applications.
5. The impact attenuator system of claim 3, wherein the
hyperelastic material comprises a thermoset cast polyurethane
system material.
6. The impact attenuator system of claim 5, wherein the
hyperelastic material comprises a polyurethane elastomer.
7. The impact attenuator system of claim 4, wherein the
hyperelastic material comprises an energy absorbing hyperelastic
material, comprising: a mixture of reactive components comprising
an MDI-polyester and/or an MDI-polyether prepolymer, at least one
long-chain polyester and/or polyether polyol, at least one
short-chain diol, and at least one catalyst, the hyperelastic
material behaving in a rate-independent hyperelastic manner and
having a permanent set that is minimized so that the hyperelastic
material absorbs tremendous amounts of impact energy while
remaining fully recoverable when used in energy-absorbing
applications, wherein the reactive components are combined in a
proportion that provides about 1-10% excess of isocyanate groups in
the total mixture.
8. The impact attenuator system of claim 7, wherein the
hyperelastic material behaves in a hyperelastic manner under
dynamic loadings of high strain rates of up to at least about
900-1000s.sup.-1 and has non-linear elastic responses in energy
absorbing applications.
9. The impact attenuator system of claim 7, wherein the polyester
component is selected from the group consisting of polyglycol
adipates and polycaprolactones, and wherein the polyether component
is selected from the group consisting of polypropylene glycol,
polyethylene glycol and combinations thereof.
10. The impact attenuator system of claim 7, wherein the reactive
components are combined in a proportion that provides about 5%
excess of isocyanate groups in the total mixture.
11. The impact attenuator system of claim 7, wherein the catalyst
contains a blend of a tertiary amine catalyst and a tin-based
catalyst.
12. The impact attenuator system of claim 11, wherein the tertiary
amine catalyst and said tin-based catalyst is in a ratio of about
4:1.
13. The impact attenuator system of claim 7, wherein a total
catalyst loading of about 0.026% by weight is used to provide a gel
time of about 2.25 to 2.50 minutes.
14. The impact attenuator system of claim 7, wherein the
hyperelastic material comprises: a mixture of an MDI-ester
prepolymer having a free isocyanate content of approximately 19%,
at least one long-chain polyester polyol comprised of
ethylene/butylene adipate diol with an OH# of approximately 56, at
least one short-chain diol comprised of 1,4 butanediol that
accounts for approximately 18% by weight of the total
hydroxyl-containing components of the mixture, and at least one
catalyst comprised of a tertiary amine catalyst and a tin-based
catalyst in a ratio of about 4:1, wherein a total catalyst loading
of about 0.026% by weight is used to provide a gel time of about
2.25 to 2.50 minutes, wherein the reactive components are combined
in a proportion that provides about 5% excess of isocyanate groups
in the total mixture, and wherein the hyperelastic material behaves
in a rate-independent hyperelastic manner and has a permanent set
that is minimized so that it absorbs tremendous amounts of impact
energy while remaining fully recoverable when used in an impact
attenuator system.
15. The impact attenuator system of claim 1, wherein the
hyperelastic member has substantially tubular or columnar shaped
sidewalls and at least one interior structural member.
16-63. (canceled)
Description
CROSS REFERENCE TO RELATED APPLICATION
[0001] This application is a divisional of application Ser. No.
10/991,080, filed Nov. 17, 2004, the disclosure of which is hereby
incorporated by reference in its entirety.
BACKGROUND OF THE INVENTION
[0002] The present invention relates to an energy absorbing
apparatus. The invention relates in general to a fully redirective
and non-gating impact attenuator apparatus.
[0003] Many types of energy absorbing devices are positioned along
highways and racetracks to prevent vehicles from crashing into
stationary structures and to lessen the injuries to occupants of
the vehicle and to lessen the impact and damage that will occur to
the vehicle.
[0004] In the past, many of these devices have been rigid
structures that restrain the vehicle from leaving the highway. One
problem is that the vehicle itself is crushed and bears the brunt
of the impact. Another problem with rigid barrier is that the
vehicle may rebound back onto the highway and into oncoming
traffic. See for example, U.S. Pat. No. 3,845,936 to Boedecker, Jr.
et al., issued Nov. 5, 1974, which discloses a rigid barrier
composed of aligned barrels.
[0005] Other types of barriers include energy absorbing barrier
devices that are placed along highways and raceways. Many types of
such barrier have been proposed. For example, one type of barrier
device uses one-time collapsible energy absorbing materials that
are crushed or broken away upon impact. These types of devices are
damaged or destroyed during impact and must be replaced after a
single impact which is time consuming, expensive and leaves the
roadway unprotected during the repair time. See for example, U.S.
Pat. No. 3,982,734, to Walker, issued Sep. 28, 1976; U.S. Pat. No.
4,321,989 to Meinzer issued Mar. 30, 1982; U.S. Pat. No. 4,352,484
to Gertz et al., issued Oct. 5, 1982; U.S. Pat. No. 4,815,565 to
Sicking et al., issued Mar. 28, 1989; U.S. Pat. No. 5,797,592 to
Machado, issued Aug. 25, 1998; U.S. Pat. No. 5,851,005 to Muller et
al., issued Dec. 22, 1998; U.S. Pat. No. 5,957,435 to Bronstad,
issued Sep. 28, 1999; U.S. Pat. No. 6,126,144 to Hirsch et al.,
issued Oct. 3, 2000; U.S Pat. No. 6,409,417 to Muller et al.,
issued Jun. 25, 2002; U.S. Pat. No. 6,536,985 to Albritton, issued
Mar. 25, 2003; US2001/0014254 to Albritton published Aug. 16, 2001;
US2002/0090260 Albritton, published Jul. 11, 2002; US2003/0175076A1
to Albritton, published Sep. 18, 2003; US2003/0234390 to Bronstad,
published Dec. 25, 2003; US2004/0016916 to Bronstad, published Jan.
29, 2004; EP 000149567A2 to DuPuis published Jul. 24, 1985;
DE003106694A1 to Urberger, published September 1982;
[0006] U.S. Pat. No. 4,674,911 to Gertz, issued Jun. 23, 1987,
relies on air chambers to supply resiliency to the barrier.
[0007] U.S. Pat. No. 4,407,484 to Meinzer, issued Oct. 4, 1983,
discloses a barrier system that relies on springs for resiliency
and attenuation of the vehicle's impact. Various barrier systems
use fluid to lessen the vehicle impact. See, for example: U.S. Pat.
No. 4,452,431 to Stephens et al., issued Jun. 5, 1984, and U.S.
Pat. No. 4,583,716 to Stephens et al., issued Apr. 22, 1986,
disclose water filled buffer cartridges that are restrained with
cables in a pivotable diaphragm. Likewise, U.S. Pat. No., 3,672,657
to Young et al., issued Jun. 27, 1972, and U.S. Pat. No. 3,674,115
to Young et al, issued Jul. 4, 1972, issued disclose liquid filled
containers arranged in a barrier system; U.S. Pat. No. 3,680,662 to
Walker et al., issued Aug. 1, 1972, shows clusters of liquid filled
buffers.
[0008] Various other systems include reusable energy absorbing
devices. For example: U.S. Pat. No. 5,112,028 to Laturner, issued
May 12, 1992; U.S. Pat. No. 5,314,261 to Stephens, issued May 24,
1994; U.S. Pat. No. 6,010,275 to Fitch, issued Jan. 4, 2000; U.S.
Pat. No. 6,085,878 to Araki et al., issued Jul. 11, 2000; U.S. Pat.
No. 6,149,134 to Banks et al, issued Nov. 21, 2000; U.S. Pat. No.
6,553,495 to Williams et al., issued Mar. 18, 2003; U.S. Pat. No.
6,554,429 to Stephens et al., issued Apr. 29, 2003; US2003/0210953
A1 to Williams et al., published Nov. 13, 2003; JP 356131848A to
Miura et al., published Oct. 15, 1981; EP 000437313A1 to Guerra,
published Jul. 17, 1991.
[0009] U.S. Pat. No. 4,237,240 to Jarre et al., issued Dec. 2,
1980, discloses a flexible polyurethane foam having a high-load
bearing capacity and a large energy absorption capacity upon
impact.
[0010] U.S. Pat. No. 4,722,946 to Hostettler, issued Feb. 2, 1988,
discloses energy absorbing polyurethane elastomers and foams. U.S.
Pat. No. 6,410,609 to Taylor et al., issued Jun. 25, 2002,
discloses low pressure polyurethane foams.
[0011] There is a need for an impact attenuator barrier system
which minimizes or prevents injury to occupants of a vehicle.
[0012] There is a further need for an impact attenuator barrier
system vehicle that is fully recoverable upon impact.
[0013] There is a further need for an impact attenuator barrier
system that is economical, reliable in operation and easy to
install and maintain.
[0014] There is a further need for an impact attenuator barrier
system that is useful in is various environments, including, for
example, public highways, racetrack, and marine applications
including protecting piers.
[0015] There is a further need for an impact attenuator barrier
system that will absorb impact energies from trucks and cars
traveling at high speeds.
[0016] There is a further need for an impact attenuator barrier
system that, when impacted, does not disintegrate and cause debris
to be scattered around the site of impact.
SUMMARY OF THE INVENTION
[0017] In one aspect, the present invention relates to an impact
attenuator barrier system for vehicle safety that benefits from the
interrelationship of a number of features: the use of a cast
thermoset polyurethane elastomeric composition in the impact
attenuator barrier system, the method of forming such elastomeric
composition using certain prescribed mixing and processing steps,
the shape of the elastomeric barrier members, and the assembly of
the barrier members into the impact attenuator barrier system.
[0018] In another aspect, the present invention relates to an
impact attenuator system having side beam assemblies and a nose
assembly secured to the side beam assemblies. The side beam
assemblies include a plurality of side panels where adjacent side
panels overlap such that the side panel members are in a nested
linear arrangement. At least one diaphragm panel is positioned
between opposing side panels and is secured to the opposing side
panels by at least one securing mechanism. The opposing side panels
and the diaphragm panels define at least one bay. At least one
hyperelastic member is positioned in the at least one bay. At least
one anchoring system includes at least one cable which secures the
side panels and diaphragm panels together.
[0019] In a specific aspect, the present invention further relates
to an impact attenuator system where the hyperelastic member
comprises an energy absorbing material that behaves in a
rate-independent hyperelastic manner such that its permanent set is
minimized so that the material maintains consistent
force-displacement characteristics over a wide range of impact
energy while remaining fully recoverable.
[0020] In another specific aspect, the present invention further
relates to a roadway barrier comprising at least one hyperelastic
member. The hyperelastic member comprises an energy absorbing
material that behaves in a rate-independent hyperelastic manner
such that its permanent set is minimized so that the energy
absorbing material maintains consistent force-displacement
characteristics over a wide range of impact velocities while
remaining fully recoverable.
[0021] In yet another specific aspect, the present invention
relates to an energy absorbing hyperelastic material which
comprises a mixture of reactive components comprising an
MDI-polyester and/or an MDI-polyether prepolymer, at least one
long-chain polyester and/or polyether polyol, at least one
short-chain diol, and at least one catalyst. The hyperelastic
material behaves in a rate-independent hyperelastic manner and has
a permanent set that is minimized so that the hyperelastic material
absorbs tremendous amounts of impact energy while remaining fully
recoverable when used in energy-absorbing applications. In certain
embodiments the reactive components are combined in a proportion
that provides about 1-10% excess of isocyanate groups in the total
mixture.
[0022] It is to be understood that the hyperelastic material is
especially suitable for use in various impact attenuating
environments and products. As such, it is within the contemplated
scope of the present invention that a wide variety of other types
of products can be made using the hyperelastic materials of the
present invention. Examples of such products include, but are not
limited to, protective gear for work and sports, including helmets
and pads, car seats, pedestal seats on helicopters, bumpers for
loading docks, and the like.
[0023] In yet another specific aspect, the present invention
relates to a method for making hyperelastic materials which
comprising combining reactive components in certain preferred
proportions and providing sufficient processing times such that
there is a desired level of reactivity. The method thereby allows
ample pour time and minimize de-mold time during manufacture.
[0024] Various objects and advantages of this invention will become
apparent to those skilled in the art from the following detailed
description of the preferred embodiment, when read in light of the
accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0025] FIG. 1 is a schematic illustration, in plan view, of one
embodiment of an impact attenuator system.
[0026] FIG. 2 is a schematic illustration, in side elevation view,
of the embodiment shown in FIG. 1.
[0027] FIG. 3 is a schematic illustration, in an end elevational
view, as taken along the line 3-3 in FIG. 2.
[0028] FIG. 4 is a schematic illustration, in side elevation, taken
along the line 4-4 in FIG. 1.
[0029] FIG. 5 is a schematic illustration, in a perspective view,
of the embodiment shown in FIG. 1.
[0030] FIG. 6 is a schematic illustration, in plan view, of the
embodiment of the impact attenuator system shown in FIG. 1 in a
compressed state.
[0031] FIG. 7 is a schematic illustration, in side elevation view,
of the embodiment shown in FIG. 2, in a compressed state.
[0032] FIG. 8 is a schematic illustration, in plan view, of another
embodiment of an impact attenuator system.
[0033] FIG. 9 is a schematic illustration, in side elevation view,
of the embodiment shown in FIG. 8.
[0034] FIG. 10 is a schematic illustration, in an end elevational
view, as taken along the line 9-9 in FIG. 8.
[0035] FIG. 11 is a schematic illustration, in side elevation,
taken along the line 11-11 in FIG. 8.
[0036] FIG. 12 is a schematic illustration, in an end elevational
view, as taken along the line 12-12 in FIG. 9.
[0037] FIG. 13 is a schematic illustration, in plan view, of the
embodiment of the impact attenuator system shown in FIG. 8 in a
compressed state.
[0038] FIG. 14 is a schematic illustration, in side elevation view,
of the embodiment shown in FIG. 9, in a compressed state.
[0039] FIG. 15 is a graph showing the low-strain summary of
hyperelastic mechanical properties at 23.degree. C.
[0040] FIG. 16 is a graph showing the mid-strain summary of
hyperelastic mechanical properties at 23.degree. C.
[0041] FIG. 17 is a graph showing the high-strain summary of
hyperelastic mechanical properties at 23.degree. C.
[0042] FIG. 18 is a graph showing representative stress-strain
curves for energy absorbing materials.
[0043] FIG. 19 is a schematic illustration of a cross-sectional
view of an alternative embodiment of a hyperelastic member useful
in the impact attenuator system.
[0044] FIG. 20 is a schematic illustration of a cross-sectional
view of an alternative embodiment of a hyperelastic member useful
in the impact attenuator system.
[0045] FIG. 21 is a schematic illustration of a cross-sectional
view of an alternative embodiment of a hyperelastic member useful
in the impact attenuator system.
[0046] FIG. 22 is a schematic illustration of a cross-sectional
view of an alternative embodiment of a hyperelastic member useful
in the impact attenuator system shown under a compression stressed,
yet resilient, state.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT(S)
[0047] In one aspect, the present invention is directed to an
impact attenuator barrier system, particularly for use in vehicle
applications such as racetracks and highways or in protecting piers
and the like.
[0048] In another aspect, the present invention provides an impact
attenuator system which incorporates an array of unique, fully
recoverable hyperelastic energy absorbing elements.
[0049] In another aspect, the present invention provides a roadway
barrier comprising at least one hyperelastic member, wherein the
hyperelastic member comprises an energy absorbing material that
behaves in a rate-independent hyperelastic manner wherein its
permanent set is minimized so that the energy absorbing material
maintains consistent force-displacement characteristics over a wide
range of impact velocities while remaining fully recoverable.
[0050] Referring now to FIGS. 1-6, one embodiment of the impact
attenuator system 10 is shown. The impact attenuator system 10
includes a first side beam assembly 12 and an opposing, or second,
side beam assembly 14. The first and second beam assemblies 12 and
14 are in opposed relationship. In the embodiments shown, the first
and second beam assemblies 12 and 14 are in opposed and parallel
relationship. It is to be understood, however, that in other
embodiments, the beam assemblies do not need to be parallel. For,
example, in certain highway applications, it is desired that the
beam assemblies have a tapered configuration in order to
accommodate abutment geometry and/or provide stage reaction force
from the system (e.g., the rear bays may incorporate a more narrow
array of energy dissipating material while the front bays
incorporate a more narrow array of energy dissipating material to
provide softer response in the early stage of impact and a more
still response as the vehicle proceeds further into the system).
The first beam assembly 12 has a first, or leading, end 15 and a
second end 16. Likewise, the second beam assembly 14 has a first,
or leading, end 17 and a second end 18.
[0051] The impact attenuator system 10 also includes a nose
assembly 19 that is secured in a suitable manner to the first end
15 of the first beam assembly 12 and to the first end 17 of the
second beam assembly 14.
[0052] Each side beam assembly 12 and 14 further includes a
plurality of side panels generally shown here as 20a, 20b, 20c, 20d
and 20e. For ease of illustration it should be understood that each
side beam assembly 12 and 14 have similar side panel members where
the side panels that comprise the side beam assembly 12 are
designated as 20a-20e and the side panels that comprise the side
beam assembly 14 are designated as 20'a-20e'; only one side will be
discussed in detail for ease of explanation. The first side panel
20a has a first end 22a and a second end 24a; likewise each
subsequent panel 20b, etc. has first ends 22b, etc., and second
ends 24b, etc. The second end 24a overlaps the first end 22b of the
adjacent panel 20b. Likewise, each adjacent panel has overlapping
first and second ends. The side panel members 20a-20e are in a
nested linear arrangement. The side panel members 20a'-20e' are
also in a nested linear arrangement. Each side panel 20 can have a
three-dimensional shape, such as a wave, or corrugated, shape, as
shown in FIGS. 3 and 5. It should be understood that the side
panels 20 can have other suitable dimensions, as will become
apparent from the following description.
[0053] Each side panel 20 generally defines at least one
longitudinally extending opening 26. As best seen in the embodiment
shown in FIG. 5, each side panel 20 has an upper longitudinally
extending opening, or slot, 26a and a lower longitudinally
extending opening, or slot, 26b that are in parallel relationship.
The slot 26a on the side panel 20a at least partially overlaps the
adjacent slot 26a on the adjacent side panel 20b; likewise, each
adjacent side panel has overlapping slots 26.
[0054] The impact attenuator system 10 further includes a plurality
of diaphragm panels generally shown here as 30a, 30b, 30c, 30d and
30e. For ease of illustration it should be understood that each
diaphragm panel can have the same features, and that only one
diaphragm panel will be discussed in detail for ease of
explanation. As best seen in FIG. 3, the each of the diaphragm
panel 30 can be comprised of first and second upright members 32
and 34 and at least one or more cross members, generally shown as
36a, 36b, 36c, 36d and 36e, which extend between the first and
second upright members 32 and 34. The first and second upright
members include a plurality of spaced apart openings 38. Each
opening 38 can receive a securing mechanism 40. In other
embodiments, the diaphragm panel 30 can have other configurations
for the cross members 36, such as formed into an X shape (not
shown) or other suitable configuration.
[0055] The first diaphragm panel 30a is positioned between opposing
side panels 20a and 20a' at substantially a right angle. The first
diaphragm panel 30a is secured to the opposing side panels 20a and
20a' by one of the securing mechanisms 40. The securing mechanism
40 can comprise at least one screw-type member 42 that can have a
head that is wider than the width of the slot 26; alternatively the
securing mechanism 40 can include at least one washer-type member
44 that axially fits over the screw-type member 42 such that the
washer-type member has length and width dimensions that are greater
than the width of the slot 26. The screw-type member 42 extends
from the outer surface of the side panel 20 through the slot 26,
through the adjacent opening 38 in the upright member 32 (or 34) of
the diaphragm panel 30, and is held in position with a suitable
locking member 46, such as a hex nut. It is to be understood that
the securing mechanism 40 is capable of being longitudinally moved
along the slot 26, as will be more fully explained below.
[0056] As at least partially assembled, the impact attenuator
system 10 includes a plurality of opposing side panels 20a-20e and
20a'-20e' and a plurality of diaphragm panels 30a-30e. As
assembled, the first opposing side panels 20a and 20a' are secured
to the first diaphragm panel 30a. That is, the first upright member
32 of the diaphragm panel 30 is secured to the first side panel 20a
and the second upright member 24 of the diaphragm panel 30a is
secured to the first opposing side panel 20a' by having securing
mechanisms 40 extend through the slots 26 in the side panels 20 and
through the adjacent opening 38 in the upright member 32 (or 34).
Likewise, the remaining side panels are secured to the remaining
diaphragm panels.
[0057] The impact attenuator system 10 thus defines a plurality of
bays 50a-50e. Each bay 50 is defined by the opposing side panels 20
and diaphragm panels 30. As best seen in FIG. 1, the bay 50a is
defined by the opposing side panels 20a and 20a' and by the
diaphragm panel 30a and the nose assembly 19. Likewise, the
remaining bays 50b-50e are defined by corresponding side panels and
diaphragm panels. It is to be understood that the impact attenuator
system 10 can include fewer or more side panels and diaphragm
panels, and that the numbers and dimensions of such side panels and
diaphragm panels will depend, at least in part, on the end use and
the object which is being protected.
[0058] The impact attenuator system 10 includes a plurality, or
array, of hyperelastic members 60. In the embodiment shown, each
hyperelastic member 60 has a substantially tubular or columnar
shaped sidewalls 62 and at least one interior structural member 64.
In the embodiment shown, the structural member 64 generally has an
X-shaped cross-section such that the structural member 64 defines
at least one internal opening 66. It is to be understood that the
hyperelastic members 60 can have specific shapes and dimensions
that best meet the end use requirements. For example, in one
embodiment, as shown in the figures herein, the hyperelastic
members 60 have a generally square pillar conformation and have an
x-shaped structural cross-section 64 which allows each hyperelastic
member 60 to most effectively absorb impact energies, as will be
further explained below. It is to be understood that the shape of
the hyperelastic member 60 can have different configurations. For
example, FIG. 19 is a schematic illustration of an alternative
embodiment of a hyperelastic member 260 having a plurality of
structural members 264 that define alternating large openings 266
and small openings 268. The hyperelastic member 260 also defines a
plurality of external openings 270 that are spaced along the
external surface 272 of the structural member 260.
[0059] FIG. 20 is a schematic illustration of an alternative
embodiment of a hyperelastic member 360 having a plurality of
structural members 364 that define alternating large openings 366,
medium openings 367, and small openings 368. The hyperelastic
member 360 also defines a plurality of external openings 370 that
are spaced along the external surface 372 of the structural member
360.
[0060] FIG. 21 is a schematic illustration of an alternative
embodiment of a hyperelastic member 460 having a plurality of
structural members 464 that define alternating triangular openings
466 and diamond shaped openings 468.
[0061] FIG. 22 is a schematic illustration of an alternative
embodiment of a hyperelastic member 560 showing the member 560 in a
temporarily compressed state and showing the member in an
uncompressed, or relaxed state, in phantom. The hyperelastic member
560 has a plurality of structural members 564 that define
triangular openings 566. The structural sections 564 at least
partially collapse into the openings 566 when the hyperelastic
member 560 is under compression. Once the compressive force is
removed, the hyperelastic member 560 reverts back to the embodiment
560' as shown in phantom.
[0062] The impact attenuator system 10 further includes first and
second anchoring systems 70a and 70b. For ease of illustration it
should be understood that each anchoring systems 70a and 70b can
have the same features, and that only one anchoring system 70 will
be discussed in detail for ease of explanation. In the embodiment
shown, the anchoring system 70 includes upper and lower cables 72
and 74 which are secured at their first ends 71 and 73,
respectively, to a first, or front, anchoring mechanism 76 such as
a loop or other device. In the embodiment shown, the upper and
lower cables 72 and 74 are secured at their second ends 75 and 77,
respectively, to second, or rear, anchoring mechanisms 80. In other
embodiments, the anchoring system 70 can comprise fewer or more
cables. The front anchoring mechanism 76 is securely anchored to
the ground (not shown) in a suitable manner at or below ground
level in front of the impact attenuator system 10. As best seen in
the embodiment shown in FIG. 4, the lower cable 74 extends through
a lower cable guide opening 82 in each of the upright members 32 in
each of the diaphragm panels 30. In the embodiment shown, the lower
cable 74 in extends in a rearward direction at approximately three
inches above ground and is attached to an anchor system (not shown)
at cable height in the rear of the impact attenuator system 10.
[0063] The upper cable 72 extends through an upper cable guide
opening 84 in each of the upright members 32 in each of the
diaphragm panels 30. In the embodiment shown, the first diaphragm
panel 30a has its upper cable guide opening 84a at a spaced apart
first distance from the lower cable guide opening 82a; the second
diaphragm panel 30b has its upper cable guide opening 84b at a
spaced apart second distance from the lower cable guide opening
82b. The first distance is less than the second distance such that
the upper cable 72 is first guided in an upward direction from the
front anchoring mechanism 76 and is guided in an upward direction
from the first diaphragm panel 30a to the second diaphragm panel
30b. Thereafter, the upper cable 72 extends from the second
diaphragm panel 30b through the diaphragm panels 30c-30e in a
rearward direction that is substantially parallel to the lower
cable 74. Both the upper cable 72 and the lower cable 74 are
anchored at the second anchoring mechanism 80. In the embodiment
shown, the portion of the upper cable 72 that extends through the
diaphragm panels 30c-30e is about fifteen inches above ground
level.
[0064] In an end-on impact where a vehicle first impacts the nose
assembly 19, as schematically shown in FIGS. 6 and 7, the impact
attenuator system 10 deforms by having the sets of nested side
panels 20a-20a'-20e-20e' telescope onto adjacent side panels; that
is, the side panels 20a-20a' through at least one set of the
adjacent side panels 20b-20b' to 20e-20e' are moved by the
impacting vehicle, allowing the impact attenuator system 10 to
deflect in the longitudinal direction. Since each set of side
panels 20a-20a'-20e-20e' is connected to the corresponding
diaphragm panel 30a-e by the plurality of individual securing
mechanisms 40 that are positioned in the corresponding slots 26,
the first set of side panels 20a-20a' is slidingly moved along the
slots 26 in the second set of side panels 20b-20b', and so on. The
distance the sets of side panels are rearwardly displaced and the
number of set of side panels that are rearwardly displaced depends
on the impact on the impact attenuator system 10. This telescoping
feature of the impact attenuator system 10 of the present invention
is intended to safely bring to a stop a vehicle that strikes the
system 10 on its end and to subsequently return the system 10 to
its original position. The number of bays 50, the number of
hyperelastic elements 60 per bay, and the geometry of the
hyperelastic elements 60 can be readily modified to accommodate
specific applications of the system 10 depending on expected range
impact energies. For example, the configuration of hyperelastic
elements 60 and the number of bays 50 shown in FIG. 1 will safely
stop a 3400-lb car impacting at a speed of 50 mph in a head-on
impact. The maximum 10 ms average ridedown acceleration in this
case is approximately 25-30 g's, which is a 70-75% reduction of the
impact force compared to a frontal impact of the vehicle into a
rigid wall at 50 mph.
[0065] The impact attenuator system 10 of the present invention
also has the ability to redirect vehicles that impact on the side
of the system 10. To accommodate such side impacts, while not
compromising the performance of the system in end-on impacts, the
side panels 20 are preferably composed of short sections of
overlapping steel or HDPE panels which distribute the impact forces
between each bay 50 of the system during side impacts. During
impacts on the side of the system 10, the impact forces are
distributed from the side panels 20 through the diaphragms 30 to
the cables 72 and 74, which act in tension to transfer the
impacting load to the anchors, thereby allowing the system to
safely redirect the vehicle away from the hazard.
[0066] Referring now to FIGS. 8-18 another embodiment of an impact
attenuator system 110 is shown which can be secured in a different
manner. The impact attenuator system 110 includes a first side beam
assembly 112 and an opposing, or second, side beam assembly 114.
The first and second beam assemblies 112 and 114 are in parallel
and opposed relationship. The first beam assembly 112 has a first,
or leading, end 115 and a second end 116. Likewise, the second beam
assembly 114 has a first, or leading, end 117 and a second end
118.
[0067] The impact attenuator system 110 also includes a nose
assembly 119 that is secured in a suitable manner to the first end
115 of the first beam assembly 112 and to the first end 117 of the
second beam assembly 114.
[0068] Each side beam assembly 112 and 114 further includes a
plurality of side panels generally shown here as 120a, 120b, 120c,
120d and 120e. For ease of illustration it should be understood
that each side beam assembly 112 and 114 have similar side panel
members where the side panels that comprise the side beam assembly
112 are designated as 120a-120e and the side panels that comprise
the side beam assembly 114 are designated as 120'a-120e'; only one
side will be discussed in detail for ease of explanation. The first
side panel 120a has a first end 122a and a second end 124a;
likewise each subsequent panel 120b, etc. has first ends 122b,
etc., and second ends 124b, etc. The second end 124a overlaps the
first end 122b of the adjacent panel 120b. Likewise, each adjacent
panel has overlapping first and second ends. The side panel members
120a-120e are in a nested linear arrangement. The side panel
members 120a'-120e' are also in a nested linear arrangement. Each
side panel 120 can have a three-dimensional shape, such as a wave,
or corrugated, shape, as shown in FIGS. 10 and 12. It should be
understood that the side panels 20 can have other suitable
dimensions, as will become apparent from the following
description.
[0069] Each side panel 120 generally defines at least one
longitudinally extending opening 126. As best seen in the
embodiment shown in FIG. 9, each side panel 120 has an upper
longitudinally extending opening, or slot, 126a and a lower
longitudinally extending opening, or slot, 126b that are in
parallel relationship. The slot 126a on the side panel 120a at
least partially overlaps the adjacent slot 126a on the adjacent
side panel 120b; likewise, each adjacent side panel has overlapping
slots 126.
[0070] The impact attenuator system 110 further includes a
plurality of diaphragm panels generally shown here as 130a, 130b,
130c, 130d and 130e. In this embodiment, the is last diaphragm
panel is designated as 130e. It should be understood, however, that
the impact attenuator system 110 can have a different number of
diaphragm panels; for consistency in explanation, the last
diaphragm panel will designated herein as 130e.
[0071] As best seen in FIGS. 8 and 19, the last diaphragm panel
130e generally has a length that is shorter than the forwardly
placed diaphragm panels. For ease of illustration it should be
understood that each remaining diaphragm panel 130a-130d can have
the same features, and that only one diaphragm panel will be
discussed in detail for ease of explanation.
[0072] As best seen in FIG. 10, each of the diaphragm panels 130
can be comprised of first and second upright members 132 and 134
and at least one or more cross members, generally shown as 136a,
136b, 136c, 136d and 136e, which extend between the first and
second upright members 132 and 134. The first and second upright
members include a plurality of spaced apart openings 138. Each
opening 138 can receive a securing mechanism 140. In other
embodiments, the diaphragm panel 130 can have other configurations
for the cross members 136, such as formed into an X shape (not
shown) or other suitable configuration.
[0073] The first diaphragm panel 130a is positioned between
opposing side panels 120a and 120a' at substantially a right angle.
The first diaphragm panel 130a is secured to the opposing side
panels 120a and 120a' by one of the securing mechanisms 140. The
securing mechanism 140 can comprise at least one screw-type member
142 that can have a head that is wider than the width of the slot
126; alternatively the securing mechanism 140 can include at least
one washer-type member 144 that axially fits over the screw-type
member 142 such that the washer-type member has length and width
dimensions that are greater than the width of the slot 126. The
screw-type member 142 extends from the outer surface of the side
panel 120 through the slot 126, through the adjacent opening 138 in
the upright member 132 (or 134) of the diaphragm panel 130, and is
held in position with a suitable locking member 146, such as a hex
nut. It is to be understood that the securing mechanism 140 is
capable of being longitudinally moved along the slot 126, as will
be more fully explained below.
[0074] As at least partially assembled, the impact attenuator
system 110 includes a plurality of opposing side panels 120a-120e
and 120a'-120e' and a plurality of diaphragm panels 130a-130e. As
assembled, the first opposing side panels 120a and 120a' are
secured to the first diaphragm panel 130a. That is, the first
upright member 132 of the diaphragm panel 130 is secured to the
first side panel 120a and the second upright member 124 of the
diaphragm panel 130a is secured to the first opposing side panel
120a' by having securing mechanisms 140 extend through the slots
126 in the side panels 120 and through the adjacent opening 138 in
the upright member 132 (or 134). Likewise, the remaining side
panels are secured to the remaining diaphragm panels.
[0075] The impact attenuator system 110 thus defines a plurality of
bays 150a-150e. Each bay 150 is defined by the opposing side panels
120 and diaphragm panels 130. As best seen in FIG. 8, the bay 150a
is defined by the opposing side panels 120a and 120a' and by the
diaphragm panel 130a and the nose assembly 119. Likewise, the
remaining bays 150b-150e are defined by corresponding side panels
and diaphragm panels. It is to be understood that the impact
attenuator system 110 can include fewer or more side panels and
diaphragm panels, and that the numbers and dimensions of such side
panels and diaphragm panels will depend, at least in part, on the
end use and the object which is being protected.
[0076] The impact attenuator system 110 includes a plurality, or
array, of hyperelastic members 160. In the embodiment shown, each
hyperelastic member 160 has a substantially tubular or columnar
shaped sidewalls 162 and at least one interior structural member
164. In the embodiment shown, the structural member generally has
an X-shaped cross-section. It is to be understood that the
hyperelastic members 160 can have specific shapes and dimensions
that best meet the end use requirements. For example, in one
embodiment, as shown in the figures herein, the hyperelastic
members 160 have a generally square pillar conformation and have an
x-shaped structural cross-section 164 which allows each
hyperelastic member 160 to most effectively absorb impact energies,
as will be further explained below.
[0077] The impact attenuator system 110 further includes first and
second anchoring systems 170a and 170b. For ease of illustration it
should be understood that each anchoring systems 170a and 170b can
have the same features, and that only one anchoring system 170 will
be discussed in detail for ease of explanation. In the embodiment
shown, the anchoring system 170 includes upper and lower cables 172
and 174 which are secured at their first ends 171 and 173,
respectively, to a first, or front, anchoring mechanism 176 such as
a loop or other device. In the embodiment shown, the upper and
lower cables 172 and 174 are secured at their second ends 175 and
177, respectively, to a second, or rear, anchoring mechanism
190.
[0078] The rear anchoring mechanism 190 includes a pair of spaced
apart and parallel support members 192a and 192b, such as I-beams.
The shorter last diaphragm panel 130e is connected to the support
members 192a and 192b by at least one or more suitable connecting
means 194 such as mounting brackets. The second end 175 of the
upper cable 172 is secured to the support member 192. The second
end 177 of the lower cable 174 is also secured to the support
member 192. The rear anchoring mechanism 190 further includes a
first elbow cable guard 196a mounted on the first I beam support
member 192a and a second elbow cable guard 196b mounted on the
second I beam support member 192b. The side beam panels 20 are
structural members with sufficient height to shield the interior
components of the system from direct impact from a vehicle and
provide adequate strength to transfer load to the diaphragms 30
when impacted at any point on the face of the panels. The materials
that the panels may be constructed from include, but are not
limited to, High Density Polyethylene, steel, aluminum, plastic,
fiber reinforced plastic and various composite materials. In
certain embodiments, it is preferred that the material be
recoverable, or semi-recoverable, produce no, or very little,
debris when impacted by a vehicle, and can withstand multiple
vehicle impacts before needing to be replaced. In the embodiment
shown, the side panels are made from corrugated sheet steel (e.g.,
10-gauge thrie-beam).
[0079] It is to be understood that, in other embodiments, the
anchoring system 170 can comprise fewer or more cables. The front
anchoring mechanism 176 is securely anchored to the ground (not
shown) in a suitable manner at or below ground level in front of
the impact attenuator system 10. As best seen in the embodiment
shown in FIG. 11, the lower cable 174 extends through a lower cable
guide opening 178 in each of the upright members 132 in each of the
diaphragm panels 130. In the embodiment shown, the lower cable 174
in extends in a rearward direction at approximately three inches
above ground and is attached to an anchor system (not shown) at
cable height in the rear of the impact attenuator system 110.
[0080] The upper cable 172 extends through an upper cable guide
opening 184 in each of the upright members 132 in each of the
diaphragm panels 130. In the embodiment shown, the first diaphragm
panel 130a has its upper cable guide opening 184a at a spaced apart
first distance from the lower cable guide opening 182a; the second
diaphragm panel 130b has its upper cable guide opening 184b at a
spaced apart second distance from the lower cable guide opening
182b. The first distance is less than the second distance such that
the upper cable 172 is first guided in an upward direction from the
front anchoring mechanism 176 and is guided in an upward direction
from the first diaphragm panel 130a to the second diaphragm panel
130b. Thereafter, the upper cable 172 extends from the second
diaphragm panel 130b through the diaphragm panels 130c-130e in a
rearward direction that is substantially parallel to the lower
cable 174. Both the upper cable 172 and the lower cable 174 are
anchored at the second anchoring mechanism 190. In the embodiment
shown, the portion of the upper cable 172 that extends through the
diaphragm panels 130c-130e is about fifteen inches above ground
level.
[0081] In an end-on impact where a vehicle first impacts the nose
assembly 119, as schematically shown in FIGS. 12-14, the impact
attenuator system 110 deforms by having the sets of nested side
panels 120a-120a'-120e-120e' telescope onto adjacent side panels;
that is, the side panels 120a-120a' through at least one set of the
adjacent side panels 120b-120b' to 120e-120e' are moved by the
impacting vehicle, allowing the impact attenuator system 110 to
deflect in the longitudinal direction. Since each set of side
panels 120a-120a'-120e-120e' is connected to the corresponding
diaphragm panel 130a-e by the plurality of individual securing
mechanisms 140 that are positioned in the corresponding slots 126,
the first set of side panels 120a-120a' is slidingly moved along
the slots 126 in the second set of side panels 120b-120b', and so
on. The distance the sets of side panels are rearwardly displaced
and the number of set of side panels that are rearwardly displaced
depends on the impact on the impact attenuator system 110.
[0082] This telescoping feature of the impact attenuator system 110
of the present invention is intended to safely bring to a stop a
vehicle that strikes the system 110 on its end and to subsequently
return the system 110 to its original position. The number of bays
150, the number of hyperelastic elements 160 per bay, and the
geometry of the hyperelastic elements 160 can be readily modified
to accommodate specific applications of the system 110 depending on
expected range impact energies. For example, the configuration of
hyperelastic elements 160 and the number of bays 150 shown in FIG.
8 will safely stop a 3400-lb car impacting at a speed of 50 mph in
a head-on impact. The maximum 10 ms average ridedown acceleration
in this case is approximately 25-30 g's, which is a 70-75%
reduction of the impact force compared to a frontal impact of the
vehicle into a rigid wall at 50 mph.
[0083] The impact attenuator system 110 of the present invention
also has the ability to redirect vehicles that impact on the side
of the system 110. To accommodate such side impacts, while not
compromising the performance of the system in end-on impacts, the
side panels 120 are preferably composed of short sections of
overlapping steel or HDPE panels which distribute the impact forces
between each bay 150 of the system during side impacts. During
impacts on the side of the system 110, the impact forces are
distributed from the side panels 120 through the diaphragms 130 to
the cables 172 and 174, which act in tension to transfer the
impacting load to the anchors, thereby allowing the system to
safely redirect the vehicle away from the hazard.
[0084] In certain embodiments the side beam assemblies form a rigid
U-shaped structure which preferably is made of a composite
material, including for example, metals such as steel, and plastics
such as high density polyethylene. The composite material is
recoverable, or semi-recoverable, produces no, or very little,
debris when impacted by a vehicle, and can withstand multiple
vehicle impacts before needing to be replaced. The hyperelastic
elements crush in the direction of impact which is the primary
energy dissipating mechanism. Because of the geometry of the
hyperelastic elements shown in the current embodiment, the
hyperelastic elements also spread outward as they crush.
[0085] In another aspect, the invention is directed to a
composition and process for forming hyperelastic elements.
[0086] The hyperelastic material used herein is a novel energy
absorbing material that behaves in a rate-independent hyperelastic
manner. The hyperelastic material behaves in a manner such that its
permanent set is minimized so that the energy absorbing material
maintains consistent force-displacement characteristics over a wide
range of impact velocities while remaining fully recoverable.
[0087] The hyperelastic material behaves in a hyperelastic manner
under dynamic loadings of high strain rates of up to at least about
900-1000s.sup.-1. The hyperelastic material uniquely allows for
direct impacts and also allows for the instantaneous recovery of
the components from which the material is made. The hyperelastic
material has non-linear elastic responses in energy absorbing
applications.
[0088] It is to be understood that the hyperelastic material is
especially suitable for use in various impact attenuating
environments and products. As such, it is within the contemplated
scope of the present invention that a wide variety of other types
of products can be made using the hyperelastic materials of the
present invention. Examples of such products include, but are not
limited to, protective gear for work and sports, including helmets
and pads, car seats, pedestal seats on helicopters, bumpers for
loading docks, and the like.
[0089] It is to be understood that elastomers belong to a specific
class of polymeric materials where their uniqueness is their
ability to deform to at least twice their original length under
load and then to return to near their original configuration upon
removal of the load. Elastomers are isotropic, nearly
incompressible materials which behave as linear elastic solids
under low strains and low strain rates. As these materials are
subjected to larger strains under quasistatic loading, they behave
in a non-liner manner. This unique mechanical behavior is called
hyperelasticity. Hyperelastic material have the ability to do work
by absorbing kinetic energy transferred from impact through an
elastic deformation with little viscous damping, heat dissipation
(from friction forces) or permanent deformation (i.e., permanent
set). This mechanical energy can then be returned nearly 100%
allowing the components to return to their original configuration
prior to impact with negligible strain.
[0090] Unfortunately, an added complexity to elastomers is their
strain rate and strain history dependence under dynamic loading,
which is called viscoelasticity. The viscoelastic nature of
elastomers causes problems resulting in hysteresis, relaxation,
creep and permanent set. Permanent set is when elastomers undergo a
permanent deformation where the material does not return to zero
strain at zero stress. This deformation however, tends to stabilize
upon repeated straining to the same fixed strain. To further add to
the complexity of the mechanical behavior of elastomers is the
visco-hyperelastic response at high strain under dynamic loading,
which is difficult to characterize and test. Often stress-strain
data from several modes of simple deformation (i.e., tension,
compression and shear) are required as input to material models,
which predict their performance.
[0091] Thus, in one aspect, the present invention uses hyperelastic
materials that absorb great amounts of mechanical energy while
maintaining full recoverability. Traditionally, the viscous
component of rubbers dominates under dynamic loading; whereby the
strain rate dependence is accounted for by visco-hyperelastic
models, where the static response is represented by a hyperelastic
model (based on elastic strain energy potential) in parallel with a
Maxwell model which takes into account strain rate and strain
history dependent viscoelasticity.
[0092] In yet another specific aspect, the present invention
relates to an energy absorbing hyperelastic material which
comprises a mixture of reactive components comprising an
MDI-polyester and/or an MDI-polyether prepolymer, at least one
long-chain polyester and/or polyether polyol, at least one
short-chain diol, and at least one catalyst. The hyperelastic
material behaves in a rate-independent hyperelastic manner and has
a permanent set that is minimized so that the hyperelastic material
absorbs tremendous amounts of impact energy while remaining fully
recoverable when used in energy-absorbing applications. In certain
embodiments the reactive components are combined in a proportion
that provides about 1-10% excess of isocyanate groups in the total
mixture.
[0093] Polyurethane elastomers are a class of materials known to
possess hyperelastic behavior. Of particular interest to the
current invention are polyurethane cast elastomer systems comprised
of an isocyanate component, typically methylene diphenyl
diisocyanate (MDI), a long chain polyol comprised of a 1000-2000 MW
polyester- or polyether-based hydroxyl-terminated polyol, and a
short chain glycol (e.g., 1,4-butanediol). Such systems are
generally mixed with a slight excess of isocyanate groups which are
available to undergo further reaction during the cure and postcure
cycle. These reactions result in a fully cured polymer system which
is slightly crosslinked and thus exhibits a high degree of
recoverability subsequent to deformation. With appropriate choice
of components, proper and unique material properties and impact
response can be achieved which make these polymer materials
suitable for hyperelastic elements in the impact attenuator barrier
system described in the current invention. The preferred
hyperelastic material has the following characteristics: Shore A
hardness values of about 90, Maximum tensile stress ranging from
about 4000 to about 7000 psi, Elongation at break ranging from
about 500 to about 700%, and Young's modulus ranging from about
4000 to about 6000 psi.
[0094] The hyperelastic elements can be formed by combining a full
MDI prepolymer system containing a long-chain polyester and/or
polyether polyol, which requires addition of a short chain glycol
as a curative, and a catalyst using a standard mixing/metering
machine. The full MDI prepolymer typically has a low % NCO, ranging
from between about 5 to 10% free isocyanate groups.
[0095] Alternatively, the hyperelastic elements can be formed by
combining a quasi MDI prepolymer system containing a long-chain
polyester and/or polyether polyol, with both a short chain glycol
and a long chain polyester and/or polyether polyol. Suitable
polyester polyols can include, without limitation, polyglycol
adipates, such as ethylene/butylene adipate, or polycaprolactones.
Suitable polyether polyols can include, without limitation,
polypropylene glycol, polyethylene glycol, or combinations
thereof.
[0096] The quasi MDI prepolymer typically has a higher % NCO,
ranging from between about 10 to 25% free isocyanate groups. The
quasi MDI prepolymer therefore can be cured with a short chain
glycol with addition, as necessary, of a long chain polyol
component, in order to achieve the desired material stiffness and
response at the impact condition.
[0097] The composition of the hyperelastic elements, when used as a
component in the impact attenuator barrier system described herein,
produces desired G-force reduction and recoverability in actual
impact tests. The prepolymer can be an MDI-polyester and/or
polyether prepolymer having a free isocyanate content of about 5 to
25%, and preferably about 19%. Suitable polyesters that can be used
with the MDI isocyanate component include, without limitation,
polyglycol adipates, such as ethylene/butylene adipate, or
polycaprolactones. Suitable polyethers that can be used with the
MDI isocyanate component can include, without limitation,
polypropylene glycol, polyethylene glycol, or combinations thereof.
The polyol can have an OH# of about 25 to 115, preferably about 35
to 80, and most preferably about 56. The short-chain diol can
include, without limitation, 1,4-butanediol, and can account for
about 10 to 20% by weight, preferably about 18% by weight of the
total hydroxyl-containing components of the mixture.
[0098] Reactive components can be combined in a proportion that
provides about 1 to 10%, preferably 5% excess of isocyanate groups
in the total mixture. A catalyst package can be utilized which
facilitates the chemical reaction of the components and allows
demolding of the parts within a reasonable time frame. The gel time
or work life of the system should not be shorter than the mold
filling time to ensure uniform material properties throughout all
sections of the part. The catalyst system can contain a blend of a
tertiary amine catalyst and a tin-based catalyst. About a 1:1 to
10:1 weight ratio, preferably about a 4:1 weight ratio, of the
amine component to the tin component will provide desirable
processing characteristics. A total catalyst loading is performed
such that the mold is filled entirely before the material begins
gelling. This level of reactivity allows ample pour time and
minimizes de-mold time during manufacture. In certain embodiments,
the chemical reactivity can be adjusted by changing the amount of
catalyst in the system.
[0099] The present invention also is directed to a process for
manufacturing the hyperelastic elements. The process includes
heating the components to process temperatures, degassing
components to remove any dissolved or entrained gases, precisely
metering components to a mix chamber, dynamically mixing the
components, and dispensing mixed material into a mold from which
the cured part is subsequently demolded and subjected to an
appropriate post cure cycle. Due to differences in component melt
points and viscosity, appropriate component temperatures, as well
as mold temperatures, may range from approximately 100.degree. F.
to 250.degree. F.
[0100] It should be understood that the examples and embodiments
described herein are for illustrative purposes only and that
various modifications or changes in light thereof will be suggested
to persons skilled in the art and are to be included within the
spirit and purview of this application.
EXAMPLE 1
Testing of the Hyperelastic Elements
[0101] A material for thermoset, cast polyurethane components for
use in making the hyperelastic elements in the impact attenuator
system was formulated. The material had a Young's modulus of at
least about 4000 to about 6000 psi and provided optimized tensile
and elongation properties at this stiffness. Samples were prepared
from a formulation having the following physical properties:
Young's modulus: 5933 psi; Tensile strength: 6830 psi; and
Elongation: 638%.
[0102] The samples were submitted for hyper-elastic testing. As
seen in the FIGS. 15, 16 and 17, the test results proved
satisfactory. FIG. 15 is a graph showing the low-strain summary of
hyperelastic mechanical properties at 23 C. FIG. 16 is a graph
showing the mid-strain summary of hyperelastic mechanical
properties at 23 C. FIG. 17 is a graph showing the high-strain
summary of hyperelastic mechanical properties at 23 C.
[0103] Further large scale testing of an impact system
incorporating the elements showed desirable properties where the
polyurethane wall elements showed high levels of G-force reduction
and recoverability of the polyurethane elements.
[0104] Large-scale testing of an energy absorption system
incorporating these hyperelastic elements showed desirable high
level of G-force reduction and recoverability of the polyurethane
elements during testing.
[0105] The mechanical performance of the material in these
large-scale tests is shown in FIG. 18, which represents the typical
stress-strain behavior of the novel energy absorbing material. It
should be noted that this material can display moderate strain rate
dependence below 10 s.sup.-1, but it is desired that for use in an
impact attenuator system, the material is desired to have minimal
strain rate dependence up to 900 to about 1000 s.sup.-1.
[0106] The hyperelastic materials having the specifications
described herein have not been in existence before this invention
thereof. Further, the hyperelastic material displays these unique
performance criteria and constraints given the high kinetic
energies, strains and strain rates involved.
EXAMPLE 2
Composition of the Hyperelastic Material
[0107] The hyperelastic material of the present invention was
prepared using an MDI-polyester prepolymer having a free isocyanate
content of approximately 19%. A separate long chain polyester
component based on ethylene/butylene adipate was utilized. The
polyol had an OH# of approximately 56. The short-chain diol
utilized was 1,4-butanediol and accounted for approximately 18% by
weight of the total hydroxyl-containing components of the
mixture.
[0108] Reactive components were combined in a proportion that
provided approximately 5% excess of isocyanate groups in the total
mixture. A catalyst package was utilized which facilitated the
chemical reaction of the components and allowed demold of the parts
within a reasonable time frame. The gel time or work life of the
system should not be shorter than the mold filling time to ensure
uniform material properties throughout all sections of the part.
The catalyst system contained a blend of a tertiary amine catalyst
and a tin-based catalyst. A 4:1 weight ratio of the amine component
to the tin component provided desirable processing characteristics.
A total catalyst loading of 0.026% by weight was used to provide a
gel time of approximately 2.25-2.50 minutes.
[0109] This level of reactivity allowed ample pour time and
minimized de-mold time during manufacture.
EXAMPLE 3
Process for Making Hyperelastic Material
[0110] A three component liquid casting machine equipped with a
precision gear pump to accurately meter components and a dynamic
mix head to obtain adequate mix quality and heating capability were
used. The prepolymer, polyol and short-chain diol reactive
components were charged into holding tanks heated to approximately
110.degree. F. Approximate amounts of the catalyst components were
added to the tank containing the short chain diol and mixed
thoroughly. All components were then degassed under a minimum
vacuum of 28 inches Hg until all dissolved gasses were removed. A
dry nitrogen pad was then applied to each tank to protect
components from moisture exposure. Pad pressure must be adequate to
ensure material feed to a suction side of a metering pump. Each
pump was calibrated to ensure delivery of an appropriate amount of
the respective component to the mix chamber. The total material
throughput was approximately 16.5 pounds per minute. A mold was
heated to an approximate range of 190.degree. F. to 210.degree. F.
prior to dispensing mixed material into the cavity. The mold
temperature was maintained at about 200.degree. F. after pouring to
ensure proper cure of the material prior to demolding the part. The
part was demolded in approximately 20 minutes and subsequently
post-cured at temperatures between about 200.degree. F. to
250.degree. F. for approximately 12 to 36 hours to ensure
completion of the chemical reaction and attainment of material
properties. The part was then aged a minimum of 21 days at ambient
conditions prior to being placed into service as a racetrack safety
barrier.
[0111] In accordance with the provisions of the patent statutes,
the principle and mode of operation of this invention have been
explained and illustrated in its preferred embodiment. However, it
must be understood that this invention may be practiced otherwise
than as specifically explained and illustrated without departing
from its spirit or scope.
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