CA2243336A1 - Reinforced composite structure - Google Patents

Abstract

A tank for storing a pressurized gas including walls of a layered material 15 and continuous fibrous bundles of fibers (16) woven through the walls of layered material (15). The continuous fibrous bundles (16 and Fig. 8) have first ends (17) that extend over a first wall of material (15), pass through the first wall of material (15), extend through the interior of the tank (11), pass through another wall of the material (15) and have second ends (17) that extend over the other wall of the material (15). Other bundles of fibers (18, 20) can be woven between different walls of the tank (11) in a similar pattern to produce complex three dimensional shapes (Figs. 3-8). In another embodiment (Fig. 9), a reinforced composite structure (29) is formed by opposed layers of material (30, 32) extending over a core (28) and continuous bundles (34) are woven in a repeating pattern through the opposed layers (30, 32) and the intermediate core (28) to form the reinforced composite structural member (29).

Description

- ' 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 , 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 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

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.

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, , 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.

, 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 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.

, _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 -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 ' 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 ~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 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 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 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 .

_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, 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.

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;

Claims (16)

1. A reinforced composite structure comprising.
a core;
first and second layers of fibrous material, the first and second layers bounding the core and having respective exterior surfaces; and a first set of continuous, fibrous bundles extending in a repeating pattern over the exterior surface of the first layer, through the first layer, through the core;
through the second layer, and over the exterior surface of the second layer.

2. The reinforced composite structure of claim 1 wherein the core is a material selected from the group consisting of clay, foam, a honeycomb metal, paper, plastics rubber, wax and wood.

3. The reinforced composite structure of claim 1 wherein the layers are a material selected from the group consisting of a fibrous composite layered material, a woven fabric, a unidirectionally oriented fiber and a randomly oriented fiber.

4. The reinforced composite structure of claim 1 wherein the fibrous bundles are made from a material selected from the group consisting of glass fibers, quartz, fibers, graphite, fibers, organic fibers and steel fibers.

5. The reinforced composite structure of claim 4 wherein the steel fibers are joined together by a lower melting point metal matrix.

6. The reinforced composite structure of claim 1 further comprising a matrix material joining the first and second layers and portions of the fibrous bundles extending over the exterior surfaces of the layers.

7. The reinforced composite, structure of claim 4 wherein the matrix material is selected from the group consisting of a thermoset resinous matrix material and a thermoplastic resinous matrix material.

8. The reinforced composite structure of claim 1 further comprising a protective layer covering respective exterior surfaces of the first and second layers and portions of the fibrous bundles extending over the respective exterior surfaces.

9. The reinforced composite structure of claim 8 wherein the protective layer is made from a material selected from the group consisting of a resinous coating, a protective film and a metal.

10. The reinforced composite structure of claim 1 further comprising an edge layer extending between edges of the first and second layers.

11. The reinforced composite structure of claim 1 wherein the fibrous bundles extend between the first and second layers in a direction substantially perpendicular to the first and second layers.

12. The reinforced composite structure of claim 1 wherein the fibrous bundles extend between the first and second layers in a direction oblique to the first and the second layers.

13. A method of making a reinforced composite structure comprising the steps of;
applying first and second layers of fibrous material around a core material; and sewing a set of continuous, fibrous bundles in a repeating pattern over the exterior surface of the first layer, through the first layer, through the core material, through the second layer, and over the exterior surface of the second layer.

14 The method of claim 13 wherein the method further comprises sewing the fibrous bundles in a generally perpendicular direction with respect to the first and second layers.

15. The method of claim 13 wherein the method further comprises sewing the fibrous bundles in an oblique direction with respect to the first and second layers.

16. The method of claim 13 wherein the method further comprises applying an edge layer extending between edges of the first and second layers.