CA1071376A

CA1071376A - Reinforced composite structure and method of fabrication thereof

Info

Publication number: CA1071376A
Application number: CA303,704A
Authority: CA
Inventors: Morris S. Loyd
Original assignee: Rockwell International Corp
Current assignee: Boeing North American Inc
Priority date: 1977-08-26
Filing date: 1978-05-18
Publication date: 1980-02-12
Also published as: GB1603019A; US4109435A

Abstract

ABSTRACT

A composite structure is reinforced and assembled utilizing barbed quill fasteners. By using such fasteners, the structure can be formed while in a staged condition. This allows co-curing and bonding of the elements of the structure in a joined condition.
Additionally, by virtue of the use of the barbed quills and their being strategically implanted in the structure, peel forces in the structural joint are minimized.

Description

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BACKGROU~D OF THE INVENTION
The present i~vention generally relates to a reinforced composite structureO More particularlyp the invention is directed to a composite structure which is reinforced and assembled utilizing bar~ed quillsO The quills~ by holding together the formed details, allow assembly of the composite structure while in a s~aged con-dition such that the entire structure can be co-cured in one operationO By vi~tue of the Lmplanted quills, the finally formed compos ite stxucture is substantially trengthened as a result of the peel forces in the joint being minimizedO
Usage of composite materials in structures has be~n increas-ing rapidlyO ~hi~ is particulaxly true in the aerospace industry where the lightweight9 high strength characteristics of these materials are paxticularly desirable. In this art, strong, light- ~:
weight, tough, ~el~-sustaining she~t material has been developed, these materials being composed a~ a class9 of a resinous sheet `: reinforced with layers of continuous, lineally aligned~ parallel filaments. ~hes~ ~heets can be forned as a single layer sheet or : as multi-layer laminate ~ and thereafter thermoset to tough9 hard, . 20 exceptionally strong panels, or skin~ ~or aircra~t and the like.
As initially foxmedJ these ~heet material~ are flexible and de~ormable~ providing panel-orming members which can be draped or otherwise conformed to various shapes and thereafter cured~ by thermosetting, upon the application of heat and pressure thereto, ~ to tough, ~trong skins or panels of permanent shape retention and - ~ havlng exceptional tensile strength imparted by the ~ontinuous ~ fiIament reinforcingO
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3~6 Panels or skins made up of these materials are exceptionally strong, lightweight structural units. However, structural joints made by the inclusion of reinforcing ribs or the like on such panels have heretofore seen limited applicability. Presently, these skins or panels are typically joined by first curing the sheet material into the desired shape and adhesively bond~ng a web or rib structure to the panel through the medium of a thenmosetting adhesive.
~owever, as previously stated, uncured composite structure is nexible and deformable. Wh~n curing large combined structural members, such as an aircraft wing box, ~if~iculties have resulted in holding the parts in place, especially when transporting an uncured structure to an autoclave or oven. Fur~her, it has been ound that tension loads, at unacceptably low values, on the ~ured panel or skin of the composite structure result in '~eel" orces which tend to separate the web a~d pan~ of the structure at their interface.

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PRIOR ART STATEMENT

Due to the ~oTmable nature of uncured composite lamina~ed sheetsS the current practice has been to mdividually cure the elements of the struc~ure prior to assembling the structure. As such, the structure is not assembled until ~he individual p~rts are cured. A
urther bonding or fasten mg operation is necessary once the structure is assembled. ~arious attempts ha~e been made to solve the peeling problem in bonded joints under tension load. musJ metal rive~s and bolts have been used as fasteners at the interface of the composite rib/sheet joints. Unfortunately, this has increased the weight of the resulting structure, increased fabrication time, required more plies of material due to the reduced laminate strength resulting from the necessary drilled fastener holes, a~d pres~nted sealing problems where the panel ~orms part of a container, such as a fuel taDX.
Imbedding a metal 'T' element into a joint has also been utilized.
This has also been ~ound to be unsatisfactory in that the element is expensi~e, increases the waight of the structure, requires a critical priming operationJ is incompatible with the surrounding material due ; to its higher thermal co-efficient o~ ~xp~nsion, and is too rigid, thereby resulting in a notch effect.
Applic~nt has found ~hat the barbed quills according to the present invention can be easily inserted into the staged structure with mini~al disturbance to the ibers and hold together the elements of the staged s~ructuIo because of th~ barbs be~omong ~nchored in the composite ibers. With balts or rive~s, holes must be drilled m the el~men*s ; of the structure which cuts the co~posite fibers, a~d ~re subject to ~he above no~ed disadvantages. Fur~her, ~h~re is normally no access

-4-1(17~376 to install corresponding fastener nuts (with of course the additional configuration problems due to protrusion of the nut). Moreover, the composite elements are too soft, even in the staged condition, for efficient hole drilling and for the bolts to effectively grip the material. It has also been found that quills according to the present invention are cheaper and lighter than bolts or rivets, can be implanted into the structure much quicker, do not waste material in that no holes are required, and resul~ in only minimal dis~urbance to the composite fibers. In addition, when strategically placed, the barbed quills add strength to the structure. This is accomplished by ~he elimination ~ " ~
; of need for holes and the a~oidance of tearing of the fibers.

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`.`i 0~ _ INVENTIO~

` It is therefore, an object of the psesent inven-tion, to providc a reinforced composite strUC~uLe with increased re~t~nce to peel orces at the joint interface.
~t is another object o the present invention to provide ~1 efficiently fastened staged composite structure with unimpaired structural strength~
It is still another object of the present invention to provide . . .
a method of a~rication which results in a rein~orced composite s~ructure .
and all~ws co-curing o the assembl~.
Briefly, in accordance with the invention, there is pro~ided a reinforced composite structure co~prising a staged composite panel, .
a staged composite web, and a plurality of quills infixed in the panel .. . .
and web. The quills have barbs thereon which enga~e the fibers of the panel and the web. The quills join the panel to the web suc~ that the s~ructure can be co-cured 3s assembled. Optimally, the quills are positioned such that the structure is reinforced when cured. Option~lly, :
a co~posite reinforcement member in the form of a generally wedge-shaped laminate is provided. In this case, the rein~orcement member would be ~ 20 b ded to ~he panel and web and also have the quills infixed thereinO; In another form of the invention, there is provided a composite st~ucture comprising a~compos~te panel, a composite ~eb, à ccmposite Teinorcement member, and a plurality of ba~bed quills infLxed in the panel, the reinforcemen~ member, and the web.
In still another oIm of the present invention, a method is . .
provided which compr;ses staging of the composîte panel and we~, : positioning the panel relative to the web, inixing a plurality o quills in :~ said panel and said web whi~e they are in a staged condition such that the web and panel ~re joined, and co-curin~ the web and p~nel as jomed~
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BRIEF DESCRIPIION OF THE DRAI~INGS

Figure 1 is a perspective view o a composite s~ructural joint according to the present invention having headed barbed q fasteners implanted therein;
Figure 2 is a perspective view of a barbed quill according : to the prese~t invention;
Figure 3 is a perspective view of another form o barbed quill;
Figure 4 is a perspective view of a composite structure illustrating headed b~bed quills as used in bo~h assembly and strengthemng of the structural joints;
Figure 5 is a perspective view of a reinforcement member; and ~ Figule 6 is a perspective view of a reinforced composite ; structure illustrating a joint strengthened by a reinforcement member in ccmbination with headed barbed quill fasteners.
: While the inve~tion will be described in c~nnection with the preferred embodiments, it will be:understood that it is not intended to limit the inv~ntion to those embodiments. On the contrary, it is intended to cover all alternatives, modiications, a~d equivalen~s that may be.included within the spirit and scope of the inYention as :~ ~ defined by the appended elaimsO

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. -7-3t76 DETAILED DESCRIPTION OF THE INVENTION

Referring now to Figure 1, there is shown according to the present invention a reinforced composite structure generally indicated at 10. Structure 10 utilizes headed barbed quills 12 and 14, which are more fully described with re~erence to Figures 2 and 3, to reinorce the structural joint which is defined by a composite web generally indicated at 16 and composite panel or skin 18. Both web 16 and panel 18 are normally lam~nates of a plurality of fiber composite plies. Web 16 is made up of opposed composite sheets 20 and 22. A portion 24 of each of sheets 20 and 22 is positioned parallel and adjacent to panel 18.
A second portion 26 of sheets 20 and 22 extends transversely to panel 18.
In the embodiment illustrated in Figure 1, the second portion 26 is approximately orthogo~ally disposed to panel 18. Sheets 20 and 24 also have a fillet portion 28 between.first portion 24 and second portion 26.
Positioned between sheets 20 ~nd 22 of web 16 and p~nel 18 is a composite filler mat~rial 30. A ~her~osetting adhesive is placed o~ the contacting sur~aces of web 16, panel 18, and filler 30, bu~ is not su~icient to hold these members in assembled condition at room temperature prior to curing.
In the uncured condition, the composite sheet materials are nexible and deormable. After conforming them to the desired shape, the composite members are, according ~o the present invention, staged which gives`th0n a stiffiness at room temperature ~Jhich allows the ~ members to be assembled and fas~ened to the desired form utilizing the : 2S quiIls hereIn described. Staging is accomplished by heating to a t~mperature normally less than the cu~ing temperatur~ and compressing the composite members~ Specifically, it has been found that graphtte ~' , 3LC37 ~L3~76 epoxy lam mates can be heated to a temperature of about 175F for about 30 minutes to one hour while simNl~aneously compressed to cause bleeding (getting rid of excess resin) to result in a member which is suitably staged for the present invention.
S In this staged condition, the composite members will still normally be too soft to allow the ins$allation of bolts in view of the di~ficulty of hole drilling. In any case, as previously mentioned, hole drilling is time consuming, wastes material, results in fuel sealing problems, cuts the composite fibers, re~uires the use of extra plies, and does not overcome the probl~m of access to ~pply the corTesponding nuts and bol~s.
Figures 2 and 3 illustrate barbed quills according to the present invention. In Figure 2, the quill generally indicated by 33 has a head 41 and a ~od portion 35 pre~erably perpendicular to head 41.
Rod 35 is pre0rably tapered to allow easy insertion into the staged composite panel and webO The dis~al~end 49 of rod 35 is pointed. By virtue o~ the pointed distal end 49 and taper of rod 35, the fibers o~ the composite laminates are spread rather than torn on insertion therein of the quills. As a result, structural strength is not impaired.
Convoluti~ns of conical barbs 37 are cut out on rod 35 such that edges 39 of barbs 37 will engage ~he fibers of the staged composite laminate upon insertion thereby p~viding an anchoring effect. Head 41 of barbed quill 33 is generally flat to provide a driving surface. Such a head is normally needed unless the laminate is thick ~where ~here ~uld be more anchoring to prevent the quill5 from being pulled from the soft laminate). Figure 3 illustrates ~nother type of quill gffnerally indicated~by 43 which would normally be used for a lam mate which w~uld ~; ~

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be relatively thicker than the type quill 33 is best suited for. Thus, quill 43 has a rod 47 having a portion 48 adjacent head 51 of constant ~ection. This prevents the thickness of rod 47 near head 51 from becoming unacceptably large due to the increasing taper from pount 53.
S The material used for the quills should be one that is compatible with composite material. Normally this would be a metallic material. Ayplicant has fo~nd that titanium tor an alloy th~reof) is particularly suitable due to its high streng~h to weight ratio.
With reference again to Figure 1, a row of barbed metallic quills such as illustrated in Figure 2 or 3 is imbedded in each of fillet portion 28 of sheets 20 and 22, through iller material 30 and into cover 18. Quills according to the present invention can be inserted into the composite structure in the staged condition very quickly, such as by i~pact hammer or optimally by ultrasonic gun.
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Suitable ultrasonic guns are manufactured by the Sonobond Corporation located in Westchester, Pennsylvania. After placing quills such a~
the type 33 or 43 into contact with composite sheets 20 and 22, the ultrasonic ~un causes such quills to vibrate while ~orcing them into the--ccmposite sheets. This vibration heats up the quills and in so .. _ . ... ..... ...
doing softe~s the staged epoxy resin which aids parting o the composite ibers o~ sheets 20 and 22 by ~ing them more pliable. In combination with the pointed and tapered shape of the quills, this results in minimal`fiber dar~ge (which otherwise would 1mpair s~ructural strength).
Quills 12 are oriented at an a~gle ~which is preferably about 45) with respect to cover 18.~ Respec~ive rnws of quills 14 can also be used to supple~ent fas~ening of portion 24 of sheets 20 and 22 to panel 18.
Quills 14 are pTe~erably oTthog~nally disposed to cover 18. Spacing of quills 12 and 14 along their respective ro~s is a ma~ter of design choice.
The length of quills 12 and 14 should be such that there is no protrusion below cover 180 7~376 Figure 4 illustrates a complex composite structure generally indicated at 54 where rows o barbed titanium quills 56 are used in joining the assembly in the staged condition. The quills 56, like quills 12 and 14 of Figure 1, allow for lay-up and co-curing of ~he composite structure as opposed to curing of each of the individual parts prior to lay-up and curing of the entire assembly. With Applicant's in~ntion, subsequent ~o lay~upS the individual parts and structure as a whole are co-cured in one operation. This allows large structures, such as a wing box which is illustrated in Figure 4, to be co-cured. It further saves time and expense of mul~iple curing operations and difficulty in joining of rigid cured parts. The barbed quills also add strength to the structuTal joints as more ~ully described hereinafter.
Curing of the assembly, such as 54, is accomplished by thexmosettmg on the application of heat and pressure to the composite struc~ure~ Typically, ~Jhen cuiing an assembly such as that shown m Pigure 4 which is of graphite epoxy material, the assembly would be placed in an autocl~ve or oven and heated to a tem~erature oE about 350F for about one hour whereupon the panels of the structure become tough and have a permanent shape retention and the assembly itself becomes permanently joined. The quills which are infixed in the structure bec~e eve~ more anchored in the structure by virtue of the resin lo~king around the barbs of the quills during curing.
With Teference again to Figure 1, under normal conditions, without the infixing of the quills of the presen~ L~venti~n; a tension load applied to panel 18 would, at undesirably low le~els, cause a peel mg o~ web 16 f~am panel 18 a~ ~illet areas 28. However, by virtue o~ quills 12, whi~h add tensile strength due to the rod o~ the ~C~7 ~L3 7 6 quills and especially due to the barbs which anchor the quill in place by interaction with the composite fibers and by virtue of the cured resin which locks around the barbs, the joint is substantially strengthened and resistance to peel increased. Cptionally, quills 14 can also be provided to further strengthen the joining of web 16 to panel 18 in the same manner. It has been found that a row aTrangement of quills 12, such as illustrated in Figure 1, is a particularly effective arrang~ment for reinforcing structure ]0. This is basically due to the strengthening of the joining of the web 16 at its tangent point connection to filler material 30 ~or load coupler 60--see Figure 6~ where peel orces are greatest.
Figure 5 illustrates a load coupler or reinforcement member generally indicated at 60. Reinforcement member 60 is normally ~ormed as a multilayer laminate by blanking the desired shape from sheets o~
composite material. The layers or sheets of the laminate are of uniform size and shape and a~e stacked to ~h~ desired length to form reinforcement member 6Q. The layers are bonded together by means of a thermosetting resin which is contained in the material itself when acquired in preimpregnated foTm. ~;
Consideration must be given to the fiber orientation in stacking ths layers of the la~onate and it is Important that the ibers of the lamina~e run in at least two directions. This is illustrated on face she~t 62 of reinforc~ment me~ber 6n wh~re longitudinal fibers 63 run in the direction of arraw 64 and transverse fibers 65 in the dirsetion ;~ 25 of arrows 66. For most embodiments, the longi*udinal and transverse fibers will optimally be or~hogonally oriented. Normally, this wqll take the fo~m of ~ 0/90 orienta~ion ~he~e the 0 axis is parallel to .

~07~376 the flat bottom 67 of base 68 of member 60. Thus, the transverse fibers are 0 fibers and the longitudinal fibers are 90 fibers. It should of course be understood-that other orientations can be used, such as -45/45, 0/85, etc., depending upon the particular geometry of the reinforcing member 60 and/or the joint to be reinforced.
As can be seen in Figure 5, reinforcement member ~load coupler) 60 is generally wedge-shaped. In this reg~rd, it is meant that the structure has an enla~ged base with sides tapeTing to a thin edge. Member 60 is generally defined by a shank 70 and a base 68.
Shank 70 has two longitudinal sides 72 and 74 which collverge OT taper to a thin upper edge 76. While the interface between shank 70 and ``
base 68 is not specifically delineated in that each layer of the laminate is pre~erably integral, such can be approximated by considering the transition at a fillet area 78 on each side of m~mber 60. Thus, base 68 extends arcuately outward from sh~nk 70. By virtue of ~his diverging arcuate con~ou~ and 1at bottom 67 of base 68, it is seen .

~hat the base 68 is taper~d as it extends from shank 70.
It can n~w be seen that a flatwise tension load on the bottom face 67 of base 68 th~ough longitudinal ibers 63 and the ;
connected transverse ~ibers 65. Since thc great majority o fibers termina~e at ~he longitudinal sides 72 and 74 of shank 70, the bulk ; of a tension force on bottGm face 67 is transferred ~Q ~he longitudinal sides 72 and 74 along fillet areas 78.
Figure 6 illustrates a reinforced composite s~ruct~re g~nerally indicated at 80 which utllizes a comb~ati~ OIC th9 load coupler 60 and barbed quills~82 a~d 84. Such a conbinati~ slibst2ntially strengthens the s*Tuctural joint generally indicated at 86 which is defined by opposed sheets 88 and 90 malcing up a web generally i~ica~ed at 92 .~

~7137~i and composite panel or s~in 94. Nonnally web 92 would be joined to l~per panel or spar cap 96. A portion 100 o~ sheets 88 and 90 is positioned parallel and adjacent to panel 94. A second portion 102 of sheets 8~ and 90 extends transveTsely to panel 9~. In the el~odiment S i~.lustrated in Fi~ure 6, second por*ion 102 is approximately orthogonally disposed to panel 94. Sheets 88 and 90 also have a fillet portion lQ4 be~.reen first poTtion 100 and second portion 102. Load coupler 60 is . posi*ioned between sheets 88 and 90 of web 92 and panel 94 such that .the bo~tom face 67 o~ coupler 60 rests directly on ~or ;s imbedded in) panel 94. As can be seen in Figure 5 and 6, the longitudinal fibers of ; reinorcement me~ber 60 are parallel to the center line ~not sh~n) o web 92 and trarLsverse fibers are parallel to panel 94. It has been ..
found that this is normally the optimal configuratian of such fibers ; Thus, a flat~ise tension load on panel 60 is distributed through : 15 member 60 to.sides 72 and 74 where there is a double shear bond joint .:
. to web 92. This effectively bypasses the peel prane fillet areas 104 because the great majority of fibers of member 60 terminate above fillet areas 104.
. Barbed quills 82 are placed in the fillet areas 104 through member 60 and into panel 94 as set forth previously. This holds the staged assembly together to enable co-cur mg as previously descri~ed and also strengthens s~ructural joint 80. Barbed quills B4 may also .~. be used for additional strengthening.
Thus it is apparent that there has been provided, in acccrdance 25. with the inventiQn, a reinforced co~posite structure and method of fabrication thereof that fully satlsfies the objectives, aims, and .~:
advantages set forth above. While the invention has been described in ~-", ~ . 14- - :
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~ 7~376 conjunction with specific embodiments thereof, it is evident that many alternatives, modifications, and variations will be apparent to those skilled in the art in light of the oregoing description.
Accordingly, it is intended to embrace all such alternatives, modifications, and variations that fall within the spirit and scope of the appended claims.

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Claims

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A reinforced composite structure comprising:
a staged composite panel, said panel having a plurality of fiber composite plies, said plies being adhesively bonded together;
a staged composite web, said web having at least one sheet of fiber composite material, said sheet having at least one layer, said sheet having three portions, a first portion positioned parallel to said panel, a second portion positioned transversely to said panel, and a fillet portion between said first and second portions; and a plurality of quills infixed in said web and said panel, said quills having barbs thereon, said barbs engaging the fibers of said panel and said web, said quills joining said fillet portion to said panel whereby said panel and said web can be co-cured as assembled.

2. The reinforced composite structure of claim 1 wherein said quills have a head and a rod, said barbs are provided on said rod, said rod is positioned approximately perpendicular to said head, said rod having a pointed distal end, and said quills are positioned such that the structure is reinforced when cured.

3. The reinforced composite structure of claim 2 wherein said quills are metallic and said rod has at least a portion thereof tapered to said distal end.

4. The reinforced composite structure of claim 3 wherein said quills are of titanium, and said quills are positioned substantially in a row along said fillet portion.

5. The reinforced composite structure of claim 1 also including a composite reinforcement member, said member comprising a generally wedge-shaped laminate, said laminate being defined by a shank and a base, said shank adjoining said base, said shank having two longitudinal sides, said base extending arcuately outward from said shank, said base being tapered in thickness as it extends from said shank, said laminate having a plurality of fiber composite sheets of uniform size and shape, said sheets of said laminate being adhesively bonded together, said sheets of said laminate being arranged such that the fibers thereof substantially distribute a tension load on said base as a shear load along said longitudinal sides of said shank, said reinforcement member being bonded to said web and said panel, said base adjoining said panel and said fillet portion of said web, and said shank adjoining said second portion of said web, said quills being infixed in said reinforcement member.

6. The reinforced composite structure of claim 2 also including a composite reinforcement member, said member comprising a generally wedge-shaped laminate, said laminate being defined by a shank and a base, said shank adjoining said base, said shank having two longitudinal sides, said base extending arcuately outward from said shank, said base being tapered in thickness as it extends from said shank, said laminate having a plurality of fiber composite sheets of uniform size and shape, said sheets of said laminate being adhesively bonded together, said sheets of said laminate being arranged such that the fibers thereof substantially distribute a tension load on said base as a shear load along said longitudinal sides of said shank, said reinforcement member being bonded to said web and said panel, said base adjoining said panel and said fillet portion of said web, and said shank adjoining said second portion of said web, said quills being infixed in said reinforcement member.

7. A reinforced composite structure comprising:
a composite panel, said panel having a plurality of fiber composite plies, said plies being bonded together;
a composite web, said web having at least one sheet of fiber composite material, said sheet having at least one layer, said sheet having three portions, a first portion positioned parallel to said panel, said first portion being bonded to said panel, a second portion positioned transversely to said panel, and a fillet portion between said first and second portion;
a composite reinforcement member, said member comprising a generally wedge-shaped laminate, said laminate being defined by a shank and a base, said shank adjoining said base, said shank having two longitudinal sides, said base extending arcuately outward from said shank, said base being tapered in thickness as it extends from said shank, said laminate having a plurality of fiber composite sheets of uniform size and shape, said sheets of said laminate being adhesively banded together, said sheets of said laminate being arranged such that the fibers thereof substantially distribute a tension load on said base as a shear load along said longitudinal sides of said shank, said reinforcement member being bonded to said web and said panel, said base adjoining said panel and said fillet portion of said web, said shank adjoining said second portion of said web; and a plurality of quills infixed in said panel, said reinforcement member, and said web.

8. The reinforced composite structure of claim 7 wherein said quills have a head and a rod, said barbs are provided on said rod, said rod is positioned approximately perpendicular to said head, said rod having a pointed distal end, and said quills are positioned to reinforce the structure.

9. The reinforced composite structure of claim 8 wherein said quills are metallic, and said shank has at least a portion thereof tapered to said distal end.

10. The reinforced composite structure of claim 9 wherein said quills are of titanium, and said quills are positioned substantially in a row along said fillet portion.

11. A method or forming a composite structure which comprises:
providing a composite panel and a composite web, said panel having a plurality of fiber composite plies, said plies being bonded together, said web having at least one sheet of fiber composite material, said sheet having at least one layer, said sheet having three portions, a first portion and a second portion which are divided by a fillet portion;
staging said panel and said web;
positioning said panel relative to said web such that said first portion is positioned parallel to said panel and said second portion is positioned transversely to said panel;
infixing a plurality of quills in said web and said panel while said web and said panel are in a staged condition such that said fillet portion is joined to said panel, said quills having barbs thereon, said barbs engaging the fibers of said panel and said web; and co-curing said web and said panel as joined.

12. The method of claim 11 wherein said infixing of said quills is such that said quills are positioned to reinforce said structure when cured.

13. The method of claim 12 wherein said quills have a head and a rod, said barbs are provided on said rod, said rod is positioned approximately perpendicular to said head, and said rod has a pointed distal end.

14. The method of claim 13 wherein said quills are metallic and said rod has at least a portion thereof tapered to said distal end.

15. The method of claim 14 wherein said quills are of titanium, and said quills are positioned in a row along said fillet portion.

16. The method of claim 11 wherein said infixing a plura-lity of quills is with an ultrasonic gun.

17. The method of claim 11 wherein said panel and said web are bonded together during said co-curing step.

18. The reinforced composite structure of claim 1 wherein said quills are positioned adjacent to said fillet portion.

19. The reinforced composite structure of claim 1 wherein said quills are positioned in said fillet portion.

20. The reinforced composite structure of claim 7 wherein said quills are positioned adjacent to said fillet portion.

21. The reinforced composite structure of claim 7 wherein said quills are positioned in said fillet portion.

22. The method of claim 12 wherein said quills are positioned adjacent to said fillet portion.

23. The method of claim 12 wherein said quills are positioned in said fillet portion.