Note: Descriptions are shown in the official language in which they were submitted.
CA 02243336 1998-07-15
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REINFORCED COMIJU~ STRUCTURE
This is ~ continu~tion-in-part of application Serial No. 081568,197
filed on December 6, 1995 and entitled TANK FOR STORING PRESSURIZEI~
GAS which is a continuation-in-part of application Serial No. 081297,232 filed
August 29, 1994 and entitled NON-CYLINDRICAL FUEL TANKS FOR
NATl)RAL GAS VEHICLES, now abandoned.
Field of the l~ ention
The present invention relates generally to the construction of
r~,in~rced composite strudures, and more particularly, to a conlposite sandwich
structure rTember.
Background of the Invention
For many years, there has been interest in dcvelopi"g and using
alternative fuels for vehicles, and particularly, overland Yehicles for e~ 'e~
automobiles, buses, trucks, etc. Over that period of time, many such vehicles
have been ret,ufilled to operate using natural gas. More recently, vvith
inaeasingly stringent air pollution standa~ds, fleets of ~lehicles that have been
retmûril~ed to operate with natural gas are more comrnon.
In currently r~lrofilled vehicles, the natural gas is often stored in
a cylindrically shaped pressurized metal vessel, such as, a steel or aluminum
tank, designed specificall~ for storing gases such as natural gas, propane,
nitrogen, etc under high pressure. The cylindrical shape o~ the tank provides
a circular cross section aboln an axis which elil,lir,ales bendin~ stresses and
CA 02243336 1998-07-15
,
-2-
helps reduce the weight of the tank. Since the c~lindrical steel natural gas
storage tank is not suitable for and cannot be readily retrofitted in place of the
- vehicle's liquid fuel storage tank, the natural gas stora~e tank is often housed
in the storage area or trunk of the vehicle, thereby eliminating or severely
5 limiting the use of the trunk for other storage. Therefore, there is a need for a
natural gas storage tank that can take the place of the vehicle's liquid fuel
storage tank Other gas storage tank designs and structures are known in the
art.
For e~a",ple, the Pechstein U S Patent No 2,156,40~ is directed
10 to a spherical container for storing fluids such as gases and liquids. The
spherical container has ~ foundation with at least three reinforcing supports
adapted to lldnsr"it the forces exerted by the dead weight and the ~eight of the
contents of the container upon the foundation The container further includes
lower struts connecled at their ends to points on the inner wall of the container
15 where the container rests on the supports to form at least one lower polygonal
frame. The container further has upper struts connected at both ends to the
inner ~vall of the container at points Iying in its hofi~ontal middle portion to forrn
at l~ast one upper polygonal frame. Inclined struts connect the comer points of
the upper and lower polygon~l frames to proYide a self supportin~ framework
20 which is ~ pted to transfer the loads due to the de~d weight and the weight of
the conten~s of the container directly upon the supports without subsldr,lially
stressin~ the walls of the container.
~ he Albrecht ~J S. Pat~nt No. 2, 296,414 is directed to heavily
CA 02243336 1998-07-15
reinforced storage tanks for liquids and gases that are present in high wlume
and have angular sides made of flat or curved plates. The stora~e tank has flat
side, top and bottom walls of metal plates. A plurality of Yertically spaced tiers
of braces are set at angles to aJjacenl vertical ~valls. Each tier has a plurality
of parallel, hori~ontal, equally spaced braces Iying in a com~non plane. Each ofthe braces forms a triangular truss with adjacent vertical walls to cause the
stresses in the bracing members and the wall plates to be compensating
stresses.
The Pflederer U.S. Patent No. 3,368,708 is directed to a filament
0 wound storage vessel capable of ~viUI~tanding high internal pressures. The
cylindrical wall of the tank is formed of helically wound, fibrous material
impregnated with thermal setting resin serving to bond fibers together as an
integral structure.
While all of the above known tanks are effective to confine a gas
15 under high pressure, the designs of the tanks are directed to their particular
application. For ~,~a, I r 'e, the design o~ the currently used steel cylindrical tank
is directed to a tank that is intended to be portable and not per",dr,enlly affixed
to any particular structure. ~her~fore, the tank has specifications relating to its
size, shape and weight that facilitate portability.
In conlrast, the Pec~stein '400 and Albrecht '414 patents are
designed to stor~ large volumes ~ pressurized g~s and are not designed for
portability. The Pflederer'708 patent is designed to have ~ removable head
portion at one end Yvhich presents different desi3n considerations and a dirrerenI
CA 02243336 1998-07-15
structure. None of the above tanks provide a tank structure that may be
construded in any desired shape as may be required for installation in a vehicle.
Further, Applicants are not aware of any of those pressurized tank structures
serving any purpose other than holdin~ a pressurized liquid or gas.
5 Summary of the Invention
The present invention pro~ides a natural gas storage tank
designed specifically for installation in motor vehicles. Further, the natural gas
storage tank of the present invention has the capability of being constructed to
any desired shape to fit the specifications and space limitations ~or installation
10 in a rnotor vehicle. Further, it has been found that an intermediate structure
created in the process o~ fabricating the tank may be used as a composite
sandwich structure.
More particularly, and in accordance ~4ith the principles of one
eu~bodi",ent of the present invention, a fuel tank for a ~lehicle powered by
15 natural gas includes a three dimensional tank outer wall stn~cture rnade of a
fibrous coi "~,osite material. The tank outer w~ll strudure has an exterior surface
and further has at least two walls bounding an interior. The fuel tank further
includes a set of continuous, fibrous bundles, for e~",ple, unidirectional,
~raided, tw~sted or monofilament fibers, extending in a repeating pattem over the
20 exterior surface of the outer wall structure on the first wall, through the first wall,
through the interior, through the second wall, and over the exterior surface of the
outer wall structure on the second wall.
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In another aspect of the invention, the first and second walls of the
tank may be parallel or may be adjacent, intersecting walls In another aspect
of the invention, the tank includes a second set of continuous, fibrous bundles
extending in a repetitive paUem over the exterior surface of the wall structure on
a third wall of the tank, through the third wall, through the interior, through a
fourth wall of the tank and over the exterior of the fourth wall.
In still another aspect of the invention, the tank includes a third set
of continuous, fibrous bundles extending in a similar repeating pattern over andthrough fifth and sixth walls of the tank. The first, second and third bundles of
10 continuous fibers rnay extend through the interior of the tank in directions
generally pel~endi~ular to each other, or, in directions that are oblique to each
other, or, in perpendicular and. oblique combinations thereof. Therefore,
advant~geously, the walls of the tank may be adjacent.
The pressurized natural gas tank construction of the present
1~ invention has the advantage of being light in ~veight and ca~a~lc of corlrining the
pressurized gas. The construc~ion permits the tank to be made in any geo",ell icshape and, prefera61y, in a noncylindrical, prismatic shape comprised of a
number of intersectin~ generally flat faces or surfaces. Therefore, the walls ofthe tank can co"~ur", to any available space in a vehicle for a tank.
In accord~"ce wit~ another e",bodi",ent of the invention, a
reinforced cGI"posite s~nd.~ieh structure ;ncludes opposed first and second
layers that extend o~er opposite sides of a core. A set of continuous, fibrous
bundles extend in a repeating pattem over an e~terior surface of the first layer,
CA 02243336 1998-07-15
,
through the hrst layer, through the core, through ~he second layer and oYer an
exterior surface of the second layer. Such a structure has a wide range of
applications and th~ desired properties of being v~ry stiff and light weight.
These and other objects and advantages of the present invention will become
5 more readily a~)parenl during the following detailed.description together with the
drawin~s herein.
Brief Descrir~tion of the Drawings
FIG. 1 is a perspective vie~ of a vehicle shown in phantom line
and containing a the natural ~as tank in accord~nce with the principles of the
1 0 invention.
FIG. 2 is a fra~",e(,tary perspective view of the vehicle with the
natural gas tank of the present invention mounted in a different orientation ~ithin
the vehicle.
FIG. 3 is a perspective view of the tank of FIG. 2 with parts
15 phantom and parts in aoss-section taken generally along the line 3-3 of FIG. 2
FIG. 4 is a hd911 ,e, lla~ per~pective vie~v of a portion of the tank of
the present invention with parts in aoss-sedion illu~(aling ~n arrangement of
fibers constituting a first fibrous network.
FIG. 5 is a rtay"~ent~y perspective view, sim;1ar to that of FIG. 4,
20 with parts in cross-section illustrating two fibrous neh4orks.
FIG. 6 is a h~y",entd~ pe~ape~ e vie~,v similar to those of FIGS.
4 and 5 ill~al,ating a three-~3i"lenâional fibrous network.
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,
FIG. 7 is a dia~r~""l,atic ~iew illu~tldling the force vectors which
operate on the tank internally due to the pressures exerted by the natural gas
under high pressure.
FIG. 8 is a ~ragmentary, cross-sectional, perspective view of a
portion of an embodiment of this invention illustrating the support of oblique
walls and the use of obliquely oriented fibrous networks.
FIG. 9 is a fragmentary, cross-sectional, perspective view of an
alternati~e embodirnent of a reinr~)roed composite structure in accordance \~vith
the principles of the present invention.
Det~iled Description of the Invention
~s will be a~par~nt from ~igs. 1 and 2, t~le vehi~e 10 conta;ns high
pressure tank gas tank 11 which, as shown, is located in the rear of the vehicle.
In fis 1, the tank is oriented with its B axis in a vertical direction, and its
longitudinal C axis suLslantially perpendicular to tlle len~th of the vehlcle. In
Fig. 2, the tank has been rotated about its longitudinal C axis so that its B axis
in a hori~ontal direction. Attached to tank 11 is fill hose line 12 which is capable
of handling the ~seo~ ~ fuel under high pressure and en~ine fuel supply line 14
which is also capable of handling the ~aceouc fuel under pressure. Pressure
can be reduced at the tank fitting by use of a pressure regulator. I ncated to the
rear of high pressure tank 11 and connel,led to fill hose 12 is a receptacle 13 for
adding additional natural gas or other fuel.
As will be appa(eu~ ~rom ~IGS. 3-B, the outer structural wall portion
CA 02243336 1998-07-15
of high pressure tank 11 is comprised of a materiai 15 which may be a fibrous
composite layered material, for example, a prepreg material, a filament wound
toe, unidirectional or woven fabric which in turn, can be a fibrous mat, braidedfabric or knitted fabric. The material 15 may bc made from unidirectionally or
randomly oriented fibers.
As is noted from FIGS. 3, 4, 5, 6 and 8, continuous, internal,
fibrous bundles 16, also referred to as "intern21 fibers", are arranged within tank
11 along the A axis as illustrated in the drawings. The fibrous bundles 16 çan
consist of monofllament line, wire or fiber that can be unidirectional, braided or
10 twisted. More specifically, the fibers can be bundles of glass, quart~, graphite,
organic and/or metal1ic fibers which are joined together. Organic fibers that may
be used include witl~out limitation aramid, nylon, polyethylene, and next
generation organ~c fibers. Metallic hbers include without limitation steel and
aluminum. The bundles of fibers rnay include either a single hber or any
15 co",bi, lation of fibers. The fibrous composite layers 15 and bundles 16 may be
coagulated togell ,er using a matrix materiall v~hich in tum can be a thermoset
or ther"~plastic resin or a metal matrix.
FYrosed portions 17 of fibrous bundles 16 are crossed over or
stitched through the fibrous composite layered materi~l 15 as shown in FIGS.
20 4, 5, 6 and 8, and can be covered with a protective layer or coating 26. The
protective layer or coating 26 can be, for e~a~ 'E, a coat;ng or protective filmsuch as rubber, urethane, vinyl, etc., or a thermoset or l~,c~,,,oplastic resin, a
metal andlor a composite fibrous overlap.
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,
_9
The continuous, fibrous bundles 16 arranged along the A axis
serve to provide ~ ,fiurc ement suL,slc,ntially perpendicular to that of reinforcing
fibrous bundles 18 and 20 shown in FIG. 6 The rei"rorcing fibrous bundles 16
pass throlJgll the rnulti-ply tank wall then exposed 17 along the exterior surface
5 of the outer structural wall and then re-enter the tank throu~h the wall. rnis
pattern is repeated seriatim to provide the internal reinforcement mainly along
the A axis resisting the internal pressure forces, which would otherwise tend to
warp the tank away from its desired three-dimensional, noncylindrical structural
configuration. The thickness of the wall 15 and the spacing of fibrous bundles
1016 and 17 can be varied as desired. Protective covering 26 can be a composite
fibrous ove~vrap or layer or it can be a resinous coating. A liner 27 can be used
on the interior surface to meet the perrneation requi~ements for specific
a~lir~tions. The liner 27 may be a urethane, silicon, isocyanate, or "TEFLON"
material.
15Continuous, fibrous bundles 18 are arranged mainly along the B
axis as is shown in FIGS. 3, ~ and 6 and are crossed over/slilched through the
walls 1~ and emanate along the outer structural wall as 19.
Asshown from FIG. 6, disposed along the C axis are reinforcing
continuous, fibrous bundles 20 whose eYr~osed ends 21 emanate from the
~0 interior of tank 11. These bundles pass through the multi-plies of the outer
structural wall and are ~Yposed on the exterior surface of the outer structùral
wall. The bundles then re-enter into the interior of tank 11 to serYe as a lateral
,_i"f~,~",ent, tying the multi-ply u/alls together so as to reinforce tank 11 from
CA 02243336 1998-07-15
-1~
forces ~~vhich would othervvise tend to push the tank out on all walls. The tanks
of this invention are ~I,aracteri~e~ as having a noncylindrical three-dimensional
tank outer wall having an exterior surface and substantially opposed wall
portions of fibrous composite wall material an~ reinforcing portions. These
5 reinforcing portions are in the form of a first set of continuous, fi~rous bundles
which traverse through the tank outer wall, and a second set of continuous,
fibrous bundles nJnning in a direction substantially perpendicular to the hrst set
and, also passing through the tank outer wall. The first set and the second set
of fibrous bundles exit and re-enter the tank outer wall to pro~/ide exposed
10 portions on the e7a~erior surfaces thereof. A protectfve layer covers the exterior
surface of the tank outer wall and these ~ ~posed portions of the fibrous bundles.
As ~ill be apparent from FIG. 7, t~e vector forces operatin~
intemally on the noncylindrical tank wal1s, ~i~h are of a multi-layered
construction sho~rn at 11, 15, exert substantially perpendicularly opposed
15 forces. Forces from the fibrous bundles shown as 22, 23 balance the gas
pressure forces shown as 24, 25. As will be appreciated, for tanks of complex
shapes, the forces shown as 22, 23 ~vill not necessarily be perpendicular. As
will be apparent from FIG. 7, the respeclive pairs of forces 22, 24 and 23, 25 are
in parallel but opposite di.tclions.
~0 The r~inror~"~g fibrous bundles are depicted two dimensionally in
axes A and C in FIG. 8. One or more additional sets of reinforcing fibrous
bundles can be located so as to be at re;nrorl_;"g positions other than
su6stdntia'1y per~endi~-~lar with respect to substantially opposed outer structural
CA 02243336 1998-07-15
'
wall portions. The fibrous reinforcing bundles can be placed at ~ngles other
than 90~ to r"~i"k,i" co~ lrY shapes and/or to minimize the number and length
of the internal reinforced fibrous bundles, therefore ,naxil"king tank volume.
Fibrous bundles \Nhich are not substanti~tly perpe~idicular to a wall surface are
5 designed to balance the forces such. that the desired tank shape is maintained.
Such georl,~trically complex non~ylindrical fuel tanks in
accordance with this invention are characteri,~d by a strudure having fiber
bundles oriented in a crossi"g substantially perpendicularly intersecting pattern
in ~ombination with fiber bundles which are arranged at angles other than
0 s~b~ldntially ninety degrees col "pared with the substantially perpendicular fiber
bundles. Such structure is illustrated in FIG. 8 and cont~ins a complex geometric
configuration having multiple plzteaus connecled by sloping spans and further
characterized by rounded or sharply rounded edge surfaces.
In a lesser complex aspect, as shown in FIGS. 3, ~ and 6, the
5 rci"forc;ng structure illustrated irlvolves plies of unidirectional tape or woven
fabric having a crossing 90~ intersecting pattern involvin3 substantially
perpendicL~lar internal reinfo, ~;er"~n~. Thus the nature of the intemal
rein~o,~l"enl and ex~ernal reinf~ rc~i"enl provided by these bundles and woven
or non-woven fabric cor,lai"ir,g thern can be varied in acco,dance with the
20 present invention depending upon the specific pressure loads and the exterior
wall engineering configuration of the tanks 11.
Fabrication
The tanks of the present invention can be made by a variety of
CA 02243336 1998-07-15
~12.
procedures, including, but not nerecsarily limited to, procedures wherein the
exterior tank wall is laid up, and in an enveloping fashion, covers a temporary
or fugitive core through which tl~e internal fibers are then stitched, or three
dimensionally braided over a mandrel in ~hich case a fugitive core is not
5 needed.
The intemal fibers or bundles of flbers as previously defined may
be joined together by a thermoset or a thermoplastic resinous rnatrix material,
or other matrix material. The metal fibers may joined by a brazing or soldering
matrix materia! that is heated with the metal fibers at a temperature and for a
10 time so that the metal flbers are joined with the matrix material but do not
become annealed. The matrix material is capable of withstanding the solvents
employed to remove the foam or other temporary, viz., fugitive, core on the one
hand or is capable of withstandin~ the temperatures at ~4hid- the foam or other
temporary core rnaterial is pyrolyzed once the intemal and external substantially
1~ perpendicular and non-perpendicular reinror~,ing fibers have been placed and
solidified at their desired locations. Woven plies of pre-i.,lpregnaled material
stitohed with pre-i",pregnated bundles of fibers can be formed by inflation
followed by curing within asse"lbled sections of a moid. Upon cooling or curing,
the tank 11 adlieves its solid, non-cylindrical, thre~dimensional desired
20 configuration.
The liner material 27 may be added by t~40 methods. The flrst
method involves placing the liner material, for example, a urethane, silicon,
isocyanate, or '~EFLON" mate~ial, over the preform and under the fibrous
CA 02243336 1998-07-15
composite material that forms the tank walls. The entire assembly is then
stitched with a set of fibrous bundles and then heat and/or pressure is applied
to fuse the liner material to the assembly. The second method involves filling
the tank ~ith a liquid, for example, a urethane, silicon, isocyanate, or '~EFLON"
5 liquid, after the preform is dissolved; and then dumping the liquid out such that
the internal surfaces of the tank are completely coated with liquid. The internally
liquid-coated tank is then cured.
Additionally, with respect to the fabrication of non-cylindrical fuel
tanks 11 three-dimensional braiding techniques using a mandrel can be
10 employed without the use of core or fugitive materials on which to construct the
tanks 11~ Braiding techniques pem it the tank 11 to retain its shape while
resisting the internal pressure forces acting thereon, such is illus~rated for
example in FIG. 7.
One such techniq~e for braiding without a core is the use of a
15 braided pre-form which has a thermoplastic re~in previously incorporated
therein. Such pre-resinified, pre-braided structures can then be heated up and
inflated to its final shape with a gas or liquid. The orientation and length of the
fibers in the braided p~e-form determine its ultim~te shape
Alte~natively, a gas material can be injected into ~he interior of the
20 resinified pre-forrn after it is plaoed within a female cavity of a rnold, e.~3, a mold
formed from sections, so that the injected gas operates to force the structure
against the mold sedion into which ultimate shape tank 11 conrolll ,s. The heat
can then be removed and the mold portions sep~rated to result in the desired
CA 02243336 l998-07-l5
-14-
configuration.
The process used to attain functional rigidity of the tank is
dependent on the matrix or resin material used. A thermosetting resin can be
cured at room or elevated temperatures and a thermoplastic is final formed at
elevated temperatures, then cooled.
The following nonlimiting example will further illustrate a storage
tank constructed in accordance with the principles of the present invention.
EXAMPI F
First, a core ~vas formed from a piece of one inch thick foam cut into a six inch
10 by six inch square. The edges of the foam were roundedl using a one-half inchro4ter bit, thereby creating a foam square with smooth sernici~cular edges
haYing a one-half inch radius and two opposed five inch by five inch surfaces
Notches were cut at the center of two opposed curved edges to receive metal
inserts. The metal inserts were made from a two indl long, one inch diameter
15 piece of aluminum rod that was sawed in half longitL~dinally to aeate an insert
with a semicircular cross-section. A longitudinal center hole ~as drilled through
the metal inserts, and the holes were tapped to accept a ~/~ pipe. The metal
inserts were then inserted into the notches so that their ends were flush with the
surface of the curved edge.
Next, three plies of three ounce per sq~are yard E~lass woven
fabric v~ere wrapped around the core, followed by three plies of twenty ounce E-glass woven fabric The second set of plies of woven fabric was rotated ninety
~eyl~es with respect to first set of plies. ~lle fabric covered foam core assembly
CA 02243336 1998-07-15
was now ready to be stitched through the thickness. The stitches were rnade
with a seventy pound tensile Strerly(~l braided "KEVLAR" line in a grid pattem.
The grid pattern had stitching along a first set of rows extending diagonally
across the opposed surfaces. Stitches also extended along a second set of
5 diagonal rows substantially perpendicul~r to the hrst set of rows. The stitclles
penetratecl the fabric approximately every 0.125 inch, and the rows of stitches
were separated by approximately 0.125 inches, thereby tying the two five inch
by five inch surfaces logeU ler. T~le fabric was cut from around the tapped holes
in the metal inserts and two ~f~ pipes were attac~ed to the assembly. Epoxy
10 resin was then squirted be~veen the fabric and the foam, using a hypodermic
needle. The resin was applied in this ~ashion to ensure the resin thoroughly
saturated the fabric The completed assembly was cured in one-half an hour
and was allowed to post~ure for one week Acetone was then used as a solvent
to dissolve the foam core, thereby forming the tank interior.
A T-fitting ~Ivith two Zerk fittin~s was connected to one of the two
1~b pipes in the cured tank assembly. A 3,000 pounds per square inch ("psi")
pressure gauge was attached to the opposite 1/~ pipe and was used to record
pressure. Testing began by first filling the tank with grease through the Zerk
fittings. ~/Vhen the tank pressure reached 600 psi, a small leak developed at one
20 of the comers. The tank pressure was raised to 1,000 psi, and it took twenty-
nine seconds for the pressure to drop from 1,000 psi to 500 psi. Pressure was
again applied to the tank, and the internal fibers began to fail at appro~i",~tely
1,300 psi. By increasing the number of stitches per square inch and/or by
CA 02243336 1998-07-15
.
_1~
changing the type of fabric or material, it is believed that a tank can be
fabricated in which an initial failure of the internal fibers will not occur until a
pressure of 10,00û psi or rnore.
While manufacturing the tanks previously described, it was
5 discovered that an intermediate structure provi~ed significant alternative uses.
I~llore specifically, ~vhen the tank is manufactured around a captive core, prior to
its removal, there is provided a very stif~, light ~/veight reinforced composite
structure. Referring to Fig. 9, the rei,lror~ed composite structure 29 is formed
by two opposed skins or layers 30, 32 of fibrous composite material applied to
10 a capti~re core 28. The core 28 may be made from clay, foam, honeycomb,
metal, paper, plastic, rubber, wax, or wood. The foarn core may be metal,
ceramic, rub~er, concrete, plastic, or a polymer material. Further, the
honeycomb core may be made from paper, cc)" I~Josite, rnetal, plastic, a polymer,
or thermoplastic material. The layers 30,32 are substantially identical to the
15 layer 15 of Fig. 8 and are made of the same co~"posite materials as previously
described with resped to the layer 15.
Continuous intemal fibrous bundles 34 are identical to the
previously described internal fibrous bundles 16 of Fig 8. HoweYer, in Fig. 9,
the fibrous bundles 34 extend in a diredion ~enerally perpendicular to the major
20 surfaces of the layers 30, 32. Alternatively, the fibrous bundles may extend in
a direction obliq~e to the major sur~ces of the layers 30, 32 as shown in
phantom by the oblique bundles 36. The bundles of fibers 34 are sewn or
threaded in a repeating pattem over an exterior surface 38 of the layer 30,
CA 02243336 1998-07-15
through the first layer 30, through the core 28, through the second layer 32 andover the exterior su~ce 40 of the second layer 32.
A side 44 or end 46 of the reinforced composite structure 29 may
be left unfinished. Altematively, the side and end surf~ces may be finished witha close out or edge layer 48 that extends between the edges 50, 52 of the
respedi\~e tayers 30, 32 The hbrous composite layers 30, 32 and bundles 34
may be coagulated together using a matrix material, ~hich in turn can be a
thermoset or thermoplastic resin or a metal matrix as previously described.
Further, e~osed portions 54 of fibrous bundles 34 are uossed o~er or stitched
0 through the fibrous composite layered material 30, 32 as described and can becovered with a protecti~e layer or coating 56 that is identical to the protective
coating 26 previously desaibed.
The te" If oroed composite structure 29 is a sandwich construction
that has the r~p~hility of being made to any desired geometry or shape to fit any
15 desired space. The r~ hrced c~,n~osite structure 2g is especially useful in the
aircraft industry and can be used to make doors, panels, wings and structural
members. In addition, the reinforced con~posit~ structure can be used in an
automobile chassis, bridges, floomllelllL,els for buildings, trailers or trucks and
grating, etc. The cornposite structure 29 has the advantages of being very stiff,
20 lightweight and capable of possessing greater strength and stiffness ~vhen
corrl~ared to other composite stnlctures. In addition, the reinforced composite
structure 29 possesses increased damage tolerance and resistance to
delamination.
CA 02243336 1998-07-15
While the invention has been set forth by a description of the
preferred embodiment in considerable detail, it is not intended to restrict or in
any way limit the claims to such detail. Additional advantages and modifications
readily appear to those who are skilled in the art. For example, the preferred
5 embodiment of the invention is a noncylindrical fuel tank for storing pressuriz~d
natural gas for powering a vehicle. As will be appreciated, the construction of
the present in~ention may be used in the construction of tanks of any geometric
shape including cylindrical tanks. Further~ tanks constructed in accordance with
the present invention may be used to store any gas under pressure, for example,
10 oxygen for aircra~ emergency supply tanks, air for ernergency rescue and scuba
tanks, nitrous oxide or other ~ne~lhetic in medical environments7 a propellant
gas for a gun or weapon, propane in a lighter weight, more portable conlai"er.
In addition, tanks constructed in accordance with the present invention may be
used for hydraulic accumulators, fire exting~isher, tankard trucksl gas storage
15 tanks for industrial or col"",ercial, etc
The inYention, therefore~ in its broadest aspects, is not limited to
the specific detail shown and described. Consequentl~, departures may be
made from the details described herein without depaning from the spirit and
scope of the claims which follow.
20 What is claimed is;
