CA1090151A - Composite tubular elements and methods for making same - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE
A composite tubular drive shaft is disclosed in which a plurality of layers of laminated sheet material is circumferentially disposed on a tubular core. The sheet material contains unidirectional fibers oriented at an angle of about 15° to about 12° with respect to the longitudinal axis of the tube.

Description

1~01~1 - ? -1 BACKG~OUND OF THE DNVENTION

2 1. Field of the Invention

3 This ~nvention relates to improved rotating ele-

4 ments. In particular, this invention relates to composite tubular elements for transmitting forces, and for sustaining 6 axial and tor~ue bearing forces.
7 2. Prior Art 8 Conventional rotating eLements intended for trans-9 mission of forces such as rotor or drive shafts are gener-ally made of metal, since these metal rotors or drive shafts 11 are believed generally to possess $~eat durability. As is 12 well known, me~l rotors or drive shafts, however, suffer 13 from a number of disadvantages. For i-nstance, it is imprac-14 tical, if not impossible, to employ a single long metal drive shaft on a truck since, as the shaft is rotated, 16 centrifugal forces act on the shaft mass. ConsequentLy, 17 any asymmetry in the shaft increases dramatically with an 18 increase in the speed at which the shaft is rotated. The 19 increased asymmetry causes the shaft to bend. Bending, however, is opposed by the elast;Lc properties of the shaft 21 metal, thereby resulting in a harmonic oscillation or vibra-22 tion. The speed at which the amplitude of vibration is 23 greatest, sometimes disastrously so, is referred to as the 24 critical speed. For a long metal shaft for a truc~, the critical speed is far too low for practical use.
26 In order to overcome the critical speed limita-27 tions of single long shafts, multiple sections of shafts `
28 are typically employed. Indeed, in the case of truck drive ~9 shafts, it is known to use up to four relatively short length solid metal cylinders in the transmission chain, one ;
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1 connected to the other by means of universal joints ant the 2 like rather than a single length of rotor shaft. At each 3 joint, bearings are required, as well as mounting brac~ets 4 and the like. These multiple components not only increase the overall weight of the truck, but more importantly 6 they tend to wear in use completely offsetting the great 7 durability normally associated with metal rotational 8 shafts.
9 Thus, the permissive circumferential speed of a rotor shaft is determined by its design and by the material 11 employed in its construction. The design of a rotor or 12 drive shaft of lighter weight and with greater axial stiff-13 ness would permit, of course, the application of such a 14 shaft in higher critical speeds than presently possible with all metal shafts as presently constructed. In the 16 past, some attempts have been made to design a lighter 17 drive shaft. For example, it is known tQ reinforce metal 18 tubes with helically wound filaments which are subsequently 19 impregnated with a resin such as an epoxy resin, thereby forming a composite structure which has a metal portion and 21 a plastic portion reinforced with continuous filament wind-22 ings. Such composite structures, while capable of with-23 standing very high circumferential speeds, suffer from 24 numerous disadvantages. For example, such helically wound rotors have inadequate axial stiffness for drive shaft 26 applicationS-27 Another difficulty associated with fiber reinforced 28 resin coatings on tubular metal shafts is associated with -~9 the significant difference in the physical properties of the two essential materials, i.e. the metal and the fiber . . . . ` .
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1 reinforced plastic. To get the requisite performance from 2 the rotor or drive shaft, both materials must be combined 3 in such a way as to operate harmoniously in absorbing and 4 transmitt~ng substantial torsion, tension and compression j loads. Also, it is worth noting that durability tends to 6 be a problem when bonding two dissimilar materials, such as 7 ~astic to metl Consequently, there still remains a need for 8 an improved rotor or drive shaft that will have the neces-9 sary strength and weight and load carrying ability and which can be economically prepared.

12 Generally speaking, the present invention provides 13 an improved tubular composite for transmitting substantial 14 torsion, tension and compression loads in which the axial loads primarily are borne by unidirectional reinforcing 16 fiber filaments embedded in a resin matrix and the primary 17 torque loads are borne by a metal tube, and in which compo-18 site structure the fibers are oriented at a predetermined 19 angle of orientati~n 90 as to compensate for the signifi-cant differences in the physical properties of the fiber 21 reinforced resin and metal tube, especially the significant 22 differences in thermal coefficients of expansion of the 23 metal tube and the fiber of the fiber reinforcéd resin.
24 Thus, in one embodiment of the present invention, there is provided a tubular composite structure for trans-26 mitting forces which comprises a metal tubular core, prefer-27 ably of aluminum, having a layer of structural metal adhe-28 sive on the exterior surface of the core. On top of the '~!9 structural adhesive layer are alternating laminae of resin impregnated unidirectional reinforcing fibers, particularly ,.. ~ .... . .

S`)~51 1 carbon or graphite fibers, and of woven fiberglass, begin- -2 ning with a lsyer of woven fiberglass followed by a lamina 3 of resin impregnated continuous unidirectional reinforcing 4 fibers and continuing in alternating fashion but ending

5 with a final layer of resin impregnated continuous

6 unidirectional reinforcing fibers, each successive layer of

7 resin impregna.te~ continuous unidirectional fihers having.

8 the fibers oriented at an angle of between about 5 to 12

9 with respect tQ the longit~dinal axis of the metal tube and in opposite orientation with respect to the next preced.ing.
11 layer. The fibers in the woven fiberglass layer are ori- ~
12 ented at 0~ and 90 with respect to the longitudinal axis of 13 the metal tubular core. PreferabLy the unidirectional con-14 tinuous reinforcing fibers are carbon fibers and particularly graphite fibers having a Youngs modulus of elasticity of 16 about30 x 106 to about 50 x 106 psi and a tensile strength of 17 about 300,000 to about 400,000 psi.
18 These and other embodiments of the present inven-19 tion will become readily apparent upon reading of the Detailed Description which follows in conJunction with the 21 drawings~

23 Figure 1 is an isometric drawing, partly in per-24 spective and partly cut away, showing the relationship of 25 the alternating sheets of glass fibers and unidirectional ~.
26 resin impregnated fiber reinfcrcing layers to the metal core.
27 Flgure 2 is an end view, partly in perspective and 28 greatly exaggerated showing the relationship of the alter-~", .' nating sheets of glass fibers and unidirectional resin impregnated reinforcing fibers arranged to be rolled on the .
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~ 1~ 9~)1 5 1 tubular metal core to form a shaft for transmitting forces 2 in accordance with the present invention.
3 Figure 3 is an exaggerated end view showing still 4 another alternate arrangement of glass fibers and unidirec-tional resin impregnated reinforcing fibers.
6 Figure 4 is an exaggerated end view showing an 7 alternate arrangement of glass fibers and unidirectional 8 resin impregnated reinforcing fibers.
9 Figure 5 is a view partly in perspective of a composite shaft.having a core longer than the reinforcing 11 fiber layer..
12 DETAILED DESCRIPTI~N ~F THE INVENTION
13 Referring. now to.the drawings, it should be noted 14 that like reference characters designate corresponding parts throughout the.several drawings and views.
16 The drive shaft of the present invention has. a 17 metal core 25 in the form of a cylindrical hollow tube as 18 i8 shown in Figure~ 1 and 2. In order that the drive shaft 19 will have the requisite strength and weight, it is preferred that the metal tube be fabricated from aluminum or magnesium 21 alloys. Indeed, it i~ particularly preferred that core 25 22 be fabricated from the following aluminum alloys: 2024, 23 7075, 7078 and 6061. The foregoing numerical designations 24 re~er, of course, to U.SO alloy compositionsO It is parti-cularly preferred that these alloys have a T-6 temper.
26 Aluminum alloys having the foregoing compcsitions and temper 27 are articles of tra.de readily available and can be shaped.
28 into tubular articles by standard techniques, such as draw- ~.
9 ing or extruding heavy walled cylindrical billets to the required dimensions.

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1 In fabricating the composite tubular element of 2 the present invention, it is important that the metal core 3 25 be completely clean. To avoid any possible surface con-4 taminants, the final cleaning of the metal core 25 generally is made with a material such as alcohol or chlorofluoro-6 carbons to remove traces of lubricants, grease, etc.
7 The metal core 25 of the present invention is en-8 cased in a sheath of resin impregnated continuous unidirec-9 tional reinforcing fibers and glass fiber fabric which is bonded to core.25 so that it i~ substantially integral 11 therewith. This sheath of resin impregnated fiber material 12 is actuaLly fabricated from various layers of material and -~
13 indeed at.lea~t two layers of fiber reinforced re~.in which :
14 are ulti~tely bonded one to the other by curlng of the ~.
resin contained therein.
16 In fabr~cating the composite tubular element., a 17 generally quadrangular, and preferably rec.tangul~r,. sheet 18 such as Lamina 26 is cut from a sheet of unidirectional 19 continuous fiber reinforcing fibers impregnated with a plastic re~in and which fibers are preferably carbon or 21 graphite fibers and which fibers will for convenienc.e be 22 hereinafter referred to as graphite fibers. As is shown 23 in the figures.,. this lamina 26 is cut with a length pre-24 ferably slightly longer than the axial length of the rein-forcing layer in the final composite tubular elementO The 26 reason for this sLight oversizing is for ease of manuac-27 ture which will become. apparent upon a further reading of 28 this detailed descriptionO The width of the rectangular :`9 fiber impregnated sheet material 26 preferably is equal to at least about twice the circumference of the metal core ': .'.
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` 1t)9)151 1 25. In other words, the width of the fiber reinforced 2 resin impregnated graphite fibers should be sufficient that 3 it can be completely wrapped around the circumference of the 4 metal core 25 at least two times. The width of the fiber impregnated sheet material can be greater; however~ it is 6 especially important that it is sized to provide only full 7 wraps and not frac~ional wraps which would make the shaft 8 unbalanced 9 The resin material impregnating the graphite fibers 22 of the quadrangular sheet 26 is a thermosetting 11 resin. Suitable thermosetting resins include epoxy and 12 polyester resins.
13 The epoxy resins are polyepoxides which are well 14 known condensation products or compounds containing oxirane rings with compounds con~aining hydroxyl groups or active 16 hydrogen atoms such as amines, acids and aldehydes. The 17 most common epoxy resin compounds are those of erichlor 18 hydrin and bis-phenol and its homologs.
19 The polyester resin is a polyccndellsation ~roduct of polybasic acids with polyhydrio alcohols. Typical poly-21 esters include polyterephthalates surh as poly(ethylene-22 terephthalate)-23 As is well known in the art, these thermoset resins 24 include modifying agents such as harde~ers and the like.
Forming such compounds is not a part of the present inven-26 tion. Indeed~ the preferred modified ep~xy resin impreg-27 nated graphite fibers are ccmmer~ially ~vailable mater;~ls;
28 for example, modified epoxy pre~impregnated graphite ~ibers ~9 are sold under the name of Rigidite 5209 and Rigidite 5213 by the Narmco Division of Celanese Gorporation, New Yor~, 6 ~k - .:

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~osr,l~l 1 NY- Other ccmmercial sources of resin pre-impregnated 2 graphite fibers are known in the industryO
3 In general, the resin impregnated quadrangular 4 sheet 26 will have a thickness of about 0.007 to 0.01 inches and contain from about 50 vclume ~/O to about 60 volume 6 c/o of graphite fibers in the thermoset resin matrix. Prefer-7 ably the quadrangular sheet 26 used in the present invention 8 has 54 volume ~/. to 58 volume ~/. of contin~ous unidirectional ~;9 graphite fibers in an epoxy resin matrix. Indeed, it is

10 especialLy preferred that the graphite fibers have a Youngs :~

11 modulus of elasticity in the range of 30x 106 to 50x 106

12 psi and a tensile strength in the range of about 300,000 to

13 about 400,000 psi.

14 . Returning again to the drawings, a woven glass fabric layer designated generally as 27 also is provided.
16 This quadrangular sheet 27 has the same dimensions as shee~..
17 26. The quadrangular sheet of woven fiberglass will have 18 a thickness of about 0.001 to about 0.002 inches and will 19 consist of woven glass fabric, preferably a fiberglass fabric known in the trade as fiberglass scrim. An espe-21 cially useful fiberglass.scrim is Style 107 sold by 22 Burlington GLass Fabrics Company, New York, NY. As can be 23 ~een, the fibers 21 of the woven fiberglass fabric are at 24 angles of 0 to 90 with respect tc the major axis of the 2S quadranguLar sheet material.
26 As can be seen in the cut~out of Figure 1, the 27 unidirectional graphite fibers 22 in quadrangular sheet 26 28 are oriented at.~.specific predetermined angle, ~1- with .29 respect to the major axis of first layer 260 In the next layer of resin impregnated unidirectional continuous , . . . .
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~: : ' '. -- . - -lO9Vl~l 1 graphite fibers, i.e layer 28, the unidirectional graph-2 ite fibers 20 are oriented at a negative predetermined 3 specific angle, ~2~ with respect to the major axis of the 4 secont layer 28. Such angle is preferably of the same dimension and9 of course, opposite sign of the angle of 6 orientation of the fibers in the first layer 260 7 In fabricating the composite shaft, a multipli-8 city of layers of resin impregnated continuous graphite 9 fibers and woven fiberglass arè cut from stock material to the desired flat pattern. Each layer is cut to the same 11 size and shapeO As indicated above, the marginal edges 12 along the minor axis of the quadrangular shaped material 13 should be sufficiently wide to accommodate at least two 14 complete turns about the tubular metal core 25. Also, as indicated previously, the major axis generally would be 16 determined by the.desired length of the shaft, and pr.efer-17 ably the~ma~r axis is slightly lon~er in Len~th.~han ~he................. .
18 longitudinal Length of the ultimate composite tubular ele-19 ment.
The various layers of sheet material are arranged 21 in alter.nating sequence starting, for example, with a bottom 22 layer of resin impregnated graphite fibers followed by a 23 layer of fiberglass, followed still by another layer of 24 resin impregnated graphlte fibers, which in turn is followed by another layer of fiberglassO In Figure ~ for example, 26 there is provided glass layers 17, 27 and 29, and graphite 27 fiber layers 26, 28 and 30 in alternating sequenceO
28 In each successive lamina of resin impregnated 29 unidirectional reinforcing fibers, however, it should be 30 noted that the reinforcing fibers are oriented at a prede-':~
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~0 90 1 5 1 1 termined angle of orientation with respect to the major 2 axis of that layerO Generally, th~s angle of orientation 3 will range between about 8 to about 12 and preferably 4 this angle of orientation will be about 10. It is parti-cularly preferred that the angle of orientaticn of the 6 graphite fibers in each succeeding layer of resin impreg-7 nated graphite sheet material be of the same magnitude but 8 opposite orientation from the next preceding layer. Thus, 9 with reference to Figure 1, fibers 22 in sheet 26 are seen being oriented at an angle, ~1- and fibers 20 of sheet 11 material 28 are oriented at an angle, ~2~ with respect to 12 the length of the quadrangular sheet material. In sheet 30 13 the fibers 22 are oriented at an angle, ~1~ with respect to 14 the longitudinal axis of the tubular core. In all instances, however, the magnitude of ~1 and ~2 are the same and they 16 are merely opposite in sign.
17 In arranging the individual lamina cut to the 18 predetermined flat pattern, it is particularly preferred to 19 form a ply of sheet material consisting of a layer of resin impregnated graphite fiber lamina having a woven fiberglass 21 lamina on top of the graphite laminae. Then, the plies are 22 placed on top of the other. Each successi~e ply, however, 23 is set back r~m the leading edge of the preceding ply in 24 an amount equal to about 1/2 the diameter of the core.
Thus, in Fi~ure 1, an outer layer of resin impregnated 26 graphite fiber 30 is followed by glass layer 29, graphite 27 layer 28, glass layer 27, graphite layer 26 and glass layer 28 17.
29 As can be seen in the arrangement of Figure 2, the first ply comprises a layer of resin impregnated graphite : . . -., . , . ~ .
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~0901'>1 1 fiber sheet material 32 on which is superimposed a fiber-2 glass layer 33. A second ply is provided comprising a layer 3 of graphite resin impregnated sheet ma~erial 30 on which is 4 superimposed a fiberglass sheet material 31. The second ply, however, is set back approximately a distance equal 6 to approximately 1/2 the diameter of the core 25. A third 7 ply, comprising a sheet of resin impregnated graphite fibers 8 28 on which is superimp~sed a layer of woven fiberglass 29, 9 is positioned to substantially correspond with the first ply. The fourth ply comprising a sheet of resin impregnated 11 graphite fiber 26 is superimposed over fiberglass layer 27 12 and this ply of sheet material is set back from the marginal 13 edge of the third ply in the same manner as the second ply 14 of material. Thus, alternating plies, comprising graphite fibers and glass fibers, are set back from the longitudinal 16 or ma~or edge of the rectangular sheet.
17 In Figure 4 is shown still another and especially 18 preferred arrangement of glass fibers and resin impregnated 19 fibers. In this embodiment, the first ply consists of a layer of resin impregnated graphite fiber sheet material 21 28 on which is placed a sheet of woven fiberglass scr~m 29.
22 Next is provided a layer of resin impregnated graphite fiber 23 26 and woven fiberglass scrim 27. In this embodiment, the 24 width of sheets 26, 27, 28 and 29 are sufficient to provide more than two full wraps around core 25. Also provided is 26 layer 19 of sufficient width to provide one full wrap 27 around core 25.
28 Layer 19 as shown in Figures 1 to 4 is a metal 29 a & esive Layer. It is particularly important in the prac-tice of the present invention that a metal adhesive layer ;,- .
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- : ' -" 1090151 1 be employed to bond the resin of the resin impregnated sheet 2 material to the tubular core 25. The metal adhesive materi-3 al employed in the practice of the present invention is one 4 typically employed for bonding plastic~ to metals, such as elastomeric modified epoxy and elastomeric modified phenol-6 urea type resins. An example of one type of a & esive is 7 polysulfide elastomer modified epichlorohydrin-bis-phenol 8 resin. Many structural adhesives are co~ ercially avail-~3t, 9 able, one of which is known as Metalbond 1133 which is an elastomer modified epoxy material sold by the Narmco Divi-11 sion of Celanese Corporation, New York, NY. Another is 12 FM 123-2 sold by American Cyanamid, Wayne,~ NJ. The struc-13 tural metal adhesive can be applied to the top side of the 14 fiberglass sheet material such as 17 of Figure 1 by means of brushing or spraying, for example, if the physical consis-16 tency of the a&esive permits, so as to cover the entire 17 top surface of the sheet. It can also be brushed or ~;
18 sprayed, for example, on the circumference of the metal 19 core 25. In the practice of the present invention, it is particularly preferred to employ an adhesive in the form of 21 a thin film of sheet material such as sheet material 19 shown 22 in Figures 1 to 4. This sheet material will be cut to the 23 same dimensions and predetermined pattern as layer 26, for 24 example, or it can be cut to provide one full wrap around core 25 as explained in conjunction with Figure 5.
26 Additionally, it has been found to be particularly -27 advantageous to also apply, by brushing or spraying, a solu-28 tion of the same adhesive used in layer 19 to the exterior 29 of the me~al core 25 after the metal core has been adequate-ly cleaned.

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9 O ~ 5 1 In general, the weight of structural metal adhe-~ 2 sive layer employed in the practice of the present invention ; 3 should be kept in the range of abou~ 0.020 to 0.040 lb/ft2, 4 and, indeed, it is particularly preferred that the weight of r, 5 adhesive layer 19 be kept to about 0.030 lb/ft2- Apparently 6 the amount of adhesive that is applied is important in ~- 7 assuring not only the proper bonding of the plastic resin 8 to the metal core but also assuring the cooperation of the 9 torsional rigidity of the metal tubing with the longitudi-nal stiffness of the graphite fiber reinforcement.
11 In any event, an oblong sheet of laminated materi-12 al consisting of a structural adhecive layer 19, resin 13 impregnated graphite fiber layers and glass fabric and a 14 multiplicity of fiber layers are wound around the circum-ference of metal core 25. It should be noted, of course, 16 that the a & esive layer is placed in contact with the tubu-17 lar metal core 25 and that the continuous unidirectional 18 graphite fiber~ are arranged at angles between +5 to +12 19 with respect to the longitudinal axis of the metal core whereas the woven fiberglass layers are arranged at angles 21 of between 0 and 90 with respect to the longitudinal axis 22 of the metal core 25. In wrapping the laminated structure 23 around metal tube core, it is particularly preferred that 24 there be very little, if any, overlap. After wrapping the metal core with the requisite layers of material, these 26 materials can be held in place by means of cellophane tape, 27 for example. Alternatively, the assembly of core and exter-28 nal resin impregnated graphite fiber reinforcing ma~erial 29 can be held in place by a wrapping of a polypropylene heat shrinkable film (not shown) which serves, in effect, as i lU 90 1 5

- 15 -1 the mold and which is subsequently removed as hereinafter 2 described.
3 After wrapping the metal core with the requisite 4 number of layers of material, the assembly is placed in an oven and heated to a temperature sufficient to cause a 6 bonding of the separate layers in the various convolutions 7 to each ather. The temperature at which the assembly is 8 heated depends upon a number of factors including the resin 9 which is used to impregnate the graphite fibers. These temperatures are well known. Typically for a modified 11 epoxy resin impregnated graphite fiber the temperature will 12 be in the range of about 100C to about 180C and preferably 13 about 140C.
14 If an external polypropylene wrapping film is used to hold the various layers around the metal core, this can

16 be removed very simply by manually peeling it away from the

17 surface of the shaft. Surface imperfections, if there are

18 any on the shaft, can be removed by sanding or 8rinding or

19 the like. If so desired, the shaft can be painted.
In those instances where particularly heavy 21 wall thickness of fiberglass scrim and resin impregnated 22 graphite fibers are to be built up on the tubular core 25, 23 after wrapping the core with a number of the multiple layers 24 and heating the assembly in an oven, additional wrappings of glass and resin impregnated fiber may be wrapped on the 26 previously cured assembly. This new assembly can be heated 27 and cured in the same manner as the original wrappings.
28 This procedure can be repeated as many times as is necessary 29 to get the requisite coating on the core.
In view of the fact that it is not always possi-.:. ... . .- : :
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1 ble to get a perfectly flat butt ed8e in the composi~e tubu-2 lar material, as indicated before it is generally preferable 3 to use a Laminated sheet material which is slightly larger 4 than the requisite length of the ultimate composite tubular element. In this way, any rounded shoulder such as shoulder 6 5 shown in Figure 5 can be eliminated merely by making a 7 radial cut through the tube behind the shoulder, thereby 8 providing a perfectly straight butt edge, if this is requir-9 ed for the composite tubular element.
The application has been described with particular 11 reference to composite shafts for transmitting substantial 12 torsion, tension and compression loads, irrespective of the 13 application for such shafts.
14 ~o further illustrate the present invention, reference now is herein made to a typical composite shaft 16 for a truck. In such application the metal core 25 typi-17 cally will be in the range of 8 to 10 feet long and have an 18 I.D. in the range of 2-3/4"to 4-1/2" and an O.D. in the 19 range of 3" to 5". The shaft will have a layer of struc-tural metal adhesive in the range of about .020 to .040 21 lb/ft2. On top of the structural adhesive layer will be 22 bonded thereto 2 to lD plies of fiberglass scrim and the 23 epoxy impregnated unidirectional continuous graphite fiber 24 sheet material, each ply consisting of a layer of scrim and a layer of the fiber sheet material. The orientation of 26 the woven glass fiber layers will be at 0 to 90 with 27 respect to the longitudinal axis of the shaft and the 28 orientation of the continuous graphite fibers. Each suc-29 ceeding layer of graphite fiber will be about 10 but in opposite direction from the next preceding layer. Thus, . .

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: 1~ 90 ~ 5 1 the graphite fiber is said to be oriented at +10 with 2 respect to the longitudinal axis.
3 In contra~t thereto, for a typical standard size 4 automobile, a composite drive shaft of the present inven-tion wouLd have an aluminum core having a length of between 6 about 40" to 72" and an O.D. between 2-1/2" to 3" and an 7 I.D. of between 2-1/4" to 2-3/4". Such composite ~riue 8 shaft would have 2 tolD plies of woven fiberglass and con-9 tinuous unidirectional graphite fibers impregnated with an epoxy resin, each ply consisting of a layer of fiberglass 11 and a layer of the resin impregnated fibers. As with the 12 drive shaft for the truck, the graphite fibers are oriented 13 at +10 with respect to the longitudinal axis of the shaft.
14 Additionally, the shaft will have interposed between the metal core and the reinforcing layer a layer of structural , ~
16 metal adhesive.
17 As indicated hereinabove, one of the difficulties 18 associated with forming a composite tubular element for the 19 transmittal of axial compressive and torque loads is that

20 there is a vast difference in the physical properties of the ~'! '

21 metal core and the fiber reinforced resin layer such that

22 each resin layer tends to operate in opposition to the other.

23 The present invention is predicated on the discovery that

24 the two very different materials in the composite can be made to cooperate one with the other and to act in harmony, 26 thereby providing a vastly improved rotor or shaft which has 27 light weight and great strength. The key to this coDpera-28 tion resides in two very important features: (a) the proper 29 orientation of the ~raphite fiber and glass in the reinforced material, and (b) the layer of structural metal ~,.~ ., .. , ~ - - , . . -. - . . ....................... .
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1 adhesive between the metal core and the continuous graphite 2 fiber reinforced layer.
3 As should be appreciated, a broad latitude in modi-4 fication and substitution is intended in the foregoing disclo-sure. Accordingly, it is appropriate that the appended claims 6 be construed broadly and in a manner consistent with the spirit 7 and scope of the invention herein.

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Claims (9)

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

1. A tubular composite rotor shaft structure for transmitting substantial torsion, tension and compression loads comprising:
a cylindrical tubular metal core;
a layer of structural metal adhesive on the exterior surface of the metal core;
a plurality of superimposed layers of resin impregnated unidirectional continuous reinforcing fibers circumferentially wrapped around said tubular metal core, each layer of said resin impregnated reinforcing fibers being generally quadrangular in shape, each layer of said resin impregnated fibers having the fibers oriented at an angle of between about 5° to 12° with respect to the longitudinal axis of the tubular metal core and in opposite orientation with respect to the next preceding layer of said resin impregnated fibers;
a layer of woven fiberglass cloth interposed between each super-imposed layer of said resin impregnated reinforcing fibers; and a layer of woven fiberglass cloth interposed between said layer of structural metal adhesive and said superimposed layers of said resin im-pregnated reinforcing fibers.

2. The structure of claim 1 wherein the resin is a thermoset resin.

3. The structure of claim 2 wherein the reinforcing fibers are fibers selected from carbon and graphite and wherein said fibers are oriented with respect to the longitudinal axis of the tubular metal core at an angle of about 10°.

4. The structure of claim 3 wherein the woven fiberglass cloth is oriented so that the fibers therein are at 0° and 90° with respect to the longitudinal axis of the tubular metal core.

5. The structure of claim 4 wherein the metal core is selected from alloys of aluminum.

6. The structure of claim 5 wherein the structural metal adhesive is present in an amount ranging from about .020 to .040 lb/ft2.

7. A composite drive shaft for transmitting forces comprising:
a cylindrical tubular metal core having a layer of structural metal adhesive from the circumference of the tubular metal core in an amount ranging from about .020 to about .040 lb/ft2;
a plurality of layers of resin impregnated unidirectional continuous reinforcing fibers wrapped around said metal core, the fibers in said fiber reinforcing layers material being selected from carbon and graphite fibers having a Youngs modulus of elasticity of about 30 x 106 to about 50 x 106 psi and a tensile strength of about 300,000 to about 400,000 psi, each layer of said resin impregnated fibers being generally quadrangular in shape, each layer of said resin impregnated fibers having a width at least twice the circumference of the tubular core and only in full increments thereof, each layer of said resin impregnated fibers disposed in an opposite angled orientation with respect to the proceeding layer of said resin impregnated fibers, said angle of orientation being between about 5° and 12° with respect to the longitudinal axis of the tubular metal core;
layers of woven fiberglass cloth interposed between alternating layers of said resin impregnated fibers, the fibers of the woven fiberglass cloth being oriented at 0° and 90° with respect to the longitudinal axis of the tubular metal core.

8. In a composite rotating element for transmitting forces having a tubular metal core encased in a fiber reinforced resin sheath, the improvement comprising:

a structural metal adhesive layer interposed between said tubular metal core and said fiber reinforced resin sheath, said structural metal adhesive being present in an amount ranging from about .020 to about .040 lb/ft2; and said reinforcing fibers comprising alternating layers of woven glass fabric and resin impregnated continuous unidirectional fibers selected from carbon and graphite, the fibers of said woven glass fabric being oriented at 0° and 90° with respect to the longitudinal axis of the metal core and said continuous unidirectional reinforcing fibers being oriented at an angle of orientation between ?5° and ?12° with respect to the longitudinal axis of the tubular metal core.

9. A composite drive shaft for a truck or car comprising:
a tubular metal core formed from an alloy of aluminum having an inner diameter in the range of from about 2-1/4" to about 4-1/2" and having an outer diameter in the range of from about 2-1/2" to about 5", said metal core having a layer of structural metal adhesive on the periphery thereof in the range of about .020 to .040 lb/ft2; and bonded to said core by said adhesive from about 2 to 10 plies of fiberglass scrim and an epoxy impregnated unidirectional continuous graphite fiber sheet material, each ply consisting of a layer of said scrim and a layer of the fiber sheet material, the orientation of the fibers of the fiberglass scrim being at 0° and 90° with respect to the longitudinal axis of the tubular core, and the orientation of the graphite fibers in said graphite fiber sheet material being at about 10° with respect to the longitudinal axis of the metal core, each layer of graphite fiber sheet material having the same angle of orientation but of opposite direction from the next preceding layer.