CA2019658A1 - Oriented fibre structure and a method for manufacturing it - Google Patents

Abstract

ABSTRACT
The object of the invention is a method for the manu-facture of an oriented fibre structure for lamination and/or pro-tective purposes, in which especially glass, carbon, aramide, borax or ceramic fibres, reinforcing fibres in general are bound to form an oriented fibre mat or corresponding structure, by means of which the fibres can be laminated inside resin or another binder and thus form a strong shell structure, in which the strength of the shell is principally based on the strength of the above-mentioned reinforcing fibres. The intention of the invention is to create a new kind of laminable fibre structure, which can be easily formed on the surface of a mould and by means of which air-bubbles can be avoided in the laminate. In accordance with the invention the reinforcing fibres are bound to the basic knitted structure consisting of one-sided loops by loops running trans-versely in the opposite direction.

Description

20196~8 The present invention concerns a laminated oriented fibre structure in which reinforcing fibres are bound to form an oriented fibre mat or corresponding knitted element, by means of which the fibres are laminated inside resin or other binder and thus form a strong shell structure and a corresponding method for manufacturing it.
Here laminate means various kinds of fibre composites in general.
In accordance with known technology, glass-fibre composite is manufactured by spreading resin on a glass-fibre mat that has been placed on top of or inside a mould. The glass-fibre can be bound into a glass-fibre mat as discontinuous fibres, or woven into a blanket structure. The problem with these is that air-bubbles tend to remain in the laminate. This phenomenon is especially problematic at corners. One blanket structure is known from the German patent application publication DE 3.304.345.
United States publication 3.201.104 shows a circular knitting machine, in which metal wire, intended to reinforce a hose, is bound into knitted fabric. In this, however, the fabric is a fairly loose net. If the fabric is drawn tight, the reinforcing wire or fibre will not remain straight, on account of which it is not suitable for glass-fibre, for instance, which loses its strength when bent.
This invention is intended to create a new type of laminated fibre structure, which can be easily formed to the sur-face of a mould, and which avoids the afore mentioned air-bubbles in a laminate. By means of the invention, it is also advantageous to use the so-called prepreg or commingled method, in which the binder is contained in the support fibre or fed next to it, so that when it is heated it hardens in the knitting into a thin shell structure. It is possible to use polyester fibre as one kind of binder. Because the support fibres are often of an elastic material, the knitted fibre draws together so that the inelastic reinforcing fibres project from the fabric. This can be control-led by arranging for one needle to be removed so that openings, from which the reinforcing fibre is made to project, are left at regular intervals in the knitted fabric. The principal advanta-ges of the invention can be listed as follows:
- by means of a suitable choice of support fibre filament and reinforcing fibre filament materials a very low specific weight can be achieved, - by means of a suitable choice of support fibre filament (e.g~ polyester) an excellent moisture absorption ability can be achieved, in which case there is little formation of air-bubbles in the laminate, - in textile products the direction of the oriented fibres can be seen immediately, in which case it is easy to place the oriented glass-fibre filaments, which have a high strength, in such a way that they carry most of the load that the laminate is intended to withstand, - the knitted fabric containing the reinforcing fibres 2 5 g - 2a - 27899-7 is elastic or flexible in every direction, so that it is easy to laminate it and especially to place it on a form corresponding to its use, - a hose-like knitted element can easily be cut both across and with the direction of the oriented fibres, which makes it possible to use the knitted element as a sheet element of a desired shape and/or size, and it is also intended to create a fibre structure that can be used for various protective purposes. In addition, the invention is intended to create a method of manufacturing the fibre structure that can be used for any fibre at all that is required to be oriented. The principal characteristics of the method in accordance with the invention appear in the accompanying Patent Claim 1. The main principle of the invention is the binding of the reinforcing fibres to a double-sided knitted fabric, in a transverse direction to the wales. The application in accordance with Patent Claim 2 firstly makes it possible to 2~19~58 W^89t07~73 ~CT~l89/~029 `~`

achl~v~ a great output ln productlon, And secondly a po~lble the manufacture Or product in nccordanca wlth Potent Claim 11. T~l~ klnd of tube e ribre structure lo partlcularly advantageous ae~ during lamlnation, it can be 5 drawn directly onto a pipe, pin, or corresponding form.
Gener~lly~ both support fibres and relnforcing flbre3 are ~llament ~ibro6, l.e. ~ndles~ fibre the method ln Potent Clalm 3 ie used to create dense knittlng 10 wlth rein~orolng tlbre~. The form Or ~ppllcation in Patent Clalm 4 has the partlcular advantage that w~sn resin is ~fectiv~ly ~uakod into the ~abrlc, it l unlikely what sir-bubble~ will fsrm. Many rein~orolng fibre do not wlthstand knots at he 6trength of aramide flbres, on the other 15 hand, is reta$ned even after they have been bent to a rsa~onab-le extent, in which case the entire fibre structure can be knltted with this fibre. Simile experiment ore also belng msde with spun glas3-~ibre.

20 In plsce of only a slngle reln~orclng fibre, it it naturally possible to use several reinforcing flbres, l.e. bunches of ~lbres. On the other hsnd, lt l not necesoary to feed reinfor-cing ~lbres to every course Or loop6. In this connection -there is no problem ln using ag the reinforcing fibre any known 25 ribre, for example glass, carbon, aramide, borax, and ceramic fibre, either a fllaments or a bunches of filaments. It is lo po~ible to uee polyamide and their derivatives as relnforclng fibre In what hollows the lnvention ls lllustra-ted by means ox examples by referrlng to the accompAnylng 30 figure, ln which Flgure 1 chow nn enalArged plct~re of the knitted fabric in accordance with the invention figure 2 shows an enlargement of another knitted fabric 35 Figure 3 shows an enlargement of a thlrd kind of knltted ~nbrl~
figure 4 shows a ho~e-like knitted fabric wo 89Jo76?3 . 2 0 1 9 6 5 8 PCT~189/~20 ,~

The knltted ~abrlc shown in Figure 1 l created with a ~o-cal-led double circular ~nltting m~mhine, in which there are verticsl cyllnd~r needl0s And horlzont~l plate needles.
Generally lt i8 po~ible to ~peak'o~ the ~trst jet of needles 5 and the 6econd jet oS needle, the sir t 4r which knlt the rlght way round end the second knit the wrong, wry round, Polye ter or other ~lbre l used ~8 ths bate eupport rlbr~ 7 1Ø the loop ment. the needl0~ on the cylinder slde are uet to knit on ev~y ~9d~ 1 e. the ~OOp8 2 in the course. the 10 needles on the plate slde, on the other hand, ore aet to knlt ln the so-called interlock 6etting, in which Gaze ln the consecutive feeding ~nittin~ ta~e6 place ~eclprocal~y. the loop knitted by thy plato naedles are marked with the referen-ce numbers 3 end 4. The rsinforcing Slbre 1 it fed to every 15 second course and it remsin~ in the channel Sormed by loops 2, 3, 4 ln dlffere~t dirQotions. The reinforcing flbres 1 remain transverse to the directlon of ohs wales 10. Because ox the lnterlock ~ettlng, the knitted f~brlc tands to contract longltu~inally, in which case the reingforcing flbres become 20 very dense. The possible projection of the reinforcing flbres la controlled by removing needles Srom the set of plate needles at regular intervals, so that the reinforcing ~lbre pro~ect~
rrom the gaps that ante surprislng advant~ge~ in lamination are gained wlth thl~ klnd of knitted fabric. Because ox the 25 projecting loops of reinforcing ~lbres, the directlon ox the fibre i6 tri-axial, which p~event~ the delamlnation of the finl~hed reinforcing et~uoture, in other words, the ~eparatlon ox it layers from each othor.

30 Naturally it i8 pos6ible for the support fibre structure to devlate from the above ln many ways. the knitted ~abrlc must hove, however, loop that ore formed ln both dlrections, both ~rlght-way round" end "wrong-why round", 80 that the rein~or-clng fibre can by led between them. Reinforclng fibres can alto 35 be knitted into a very 10088 6mooth knltted fabrlc. The dia~ater~ ox tha cylinder ox ~nlttlng machines ln general use range from 5/8~' to 36 I. By using a larger machine lt i8 possible to efficiently manufacture wide ~lbre mats, as the Jose can be cut open and spread out a a Nat. For example, a 2~96~8 ~'~89/0~673 . PCT~189/~20 36" m~chlne can maze fibre cloth bout 2.8 metres wide During lamination alternatlng layer con be placed cross-wi~e, BO that the ~tr~ngth of the lAmlnate it squally great tn ill dlrec-lion On the othQr hind, lt lo vory easy to ~ohieve the 5 l~mlnatlon ox ho~e-llke produot~ wlth ho~e-llke f lbre ~tructur~r A spiral direGtlon ror the reln~orclng ~lbres l.
exactly rlght when conslderlng, or ex~mpl~, pre~ure loading.

In thQ ~acond adYnntaseou~ form ox r~all~atlon ox the lnvention lO the orlentod reln~orolng ~ibre~ ' run ln tha way shown in Figure 2 above and below the loop 13 and 14 of the support ~ibre~ in a straight direction and parallel to one another in the channol wormed botw~en the courses ll and 12 every thlrd course, thy belng perpendicular to the walQs lO in such a way lS that ouch rlght-wAy wound loop l4 or the courses ll end 12 thst contaln the support flbree 2 enclo6e benaath them one rein~or-clng fibre l. In order to achieve this kind of 6upport fibre ~ilam~nt a~r~ngem~nt an amount.oS support ribre ~llament~
corresponding to the course num~sr l/4 lo used in a clrcular 20 knlttlng machine. the filaments are led to the needle rlng from feedlng points located perlpherlcally at regular lnter-~818. A quantlty of loop flbre filament oorre6ponding to 3/4 ore led prom the ~eedlnq polnts ~$tu~ted it regular intervals on the ne4dl~ ring. When the ~ou;r6e number le ths above-men-25 tloned 36, thers ore g support fibre filaments and 27 loopflbre SllAment6. In the knltted olem~nt then produced, a number of the firEt end second course nd 12 are knltted together wlthout the support fibre l being dropped between them. In the directlon ox the wales lO, each cour6e ll, 12 containing 30 support flbre 1 ls followed by it least one course wlthout a support fibre f llam~nt.

Figure 3 shows till one more ~davantageous knltted element already touched on ln the prevlous for ox nppllc~tlon, whlch 35 iB formed according to the second form of realizatlon of the lnvention, wlth the diS~erence that ln plaoe of one support fibre l, sevsral, ln this cave three, parallel support f ~bre ent~ ore laid from one ceding point at a time on top of the first course if hub in this cay etch course ll, 12 con-W0~ 7673 2 019 6 8 PCT/F189/~20 tainlng sevoral parallel support fibre l are followed, in thedlrectlon of the wales lO0, by two support fibre courses that hove no support fibre filament6. In a corresponding manner, blnder ~ibre~ own be laid together wlth the r~lnforcing fibre.

Flgure 4 chow a hose-like knitted fabric 5, Srom which a rlbbon-l$ke flbre etructure l obtalned. The hose-like fabric ls divlded into narrow trips 6, to Welch no reinrorcing fibre fed. who knltted ~brio can easily be cut open at the edge lO Or the trip 8 and thu the above-mentioned ribbon-like product con be obtained. Flgure 4 how clearly that the wales 10 run perpendicularly in the hose-liku f3brlc, wherea6 the reinfor-aing fibs 1 Hun round the ~abrio in a spiral.

15 In one test knltted fabric the ratlo ox glas~-Slbre and polyester fllaments was nbout 50/50. In this way a low speclfic waight was achleved ror the laminate, only 1.3 g/cm3. The theoretical density ox hollow sphere wlth a diameter ox lO0 mm and a wall thicknesa ox 2.5 em would be bout 0.2 g/cm3 with 20 thl~ laminate.

A method, on which the ~lbre l ~lr~t treated 50 that when at re6t lt ~88ume8 a ~plral or twlsted form, BO that ln the ~inlsh~d product lt tend to contract, can be ~pplled especlal-25 ly to aramldes. In this way lt l possible to make the knlttedr~brlc elastic nlso ln the dlrectlon of the reinforclng ~ibres.

Claims (12)

1. A method for the manufacture of an oriented fibre structure to he laminated, in which reinforcing fibres (1) are bound to form an oriented fibre mat or corresponding knitted element, by which the fibres (1) are laminated inside resin or other binder and thus a strong shell structure is formed, characterized in that the knitting is carried out on a so-called double circular knitting machine, in such a way that the knitting includes the following sequential and continually repeating stages in manufacture, a) the first loop (2) is made by the first set of needles, b) at least one reinforcing fibre (1) to be included in the knitted fabric is oriented and laid on top of the above-mentioned first loop, and c) a second loop (3, 4) is knitted by the second set of needles on top of the oriented reinforcing fibre and attached to the above-mentioned first loop (2), in which case the oriented reinforcing fibre (1) runs with the support of the loops (2, 3, 4) and straight between the courses in the channel formed by them.

2. A method of manufacture in accordance with Patent Claims 1, characterized in that the needles on the cylinder side are essentially arranged to knit in each feed and the dial or corresponding needles are arranged to reciprocally by-pass, i.e.
they are set to the so-called interlock position, so that the knitted fabric is made to contract longitudinally.

3. A method of manufacture in accordance with any of Patent Claims 1 - 2, characterized in that polyester or other fibre that absorbs resin well is used as the support fibre (7).

4. A method of manufacture in accordance with any of Patent Claims 1 - 3, characterized in that more that one fibre (1) is laid in parallel on top of the above-mentioned first loop (2).

5. A method of manufacture in accordance with any of Patent Claims 1 - 4, characterized in that a part of the courses of the above-mentioned first and second loops (2, 3, 4) are knitted together without the above-mentioned support fibre filament being laid between them.

6. A method of manufacture in accordance with any of Patent Claims 1 - 7, characterized in that aramide or spun glass-fibre is used as the support fibre (7).

7. A method of manufacture in accordance with any of Patent Claims 1 - 6, characterized in that the support fibre contains binder for lamination, which is made to react by the effect of heat or in some other manner, and which then makes it possible to manufacture a strong shell structure by means of the so-called prepreg method.

8. A method of manufacture in accordance with any of Patent Claims 1 - 5, characterized in that one needle has been removed at regular intervals from one side, most advantageously from the plate needles' side, in which case the reinforcing fibre is made to project from the opening thus created in the knitted fabric.

9. A fibre structure to be laminated, in which reinforcing fibres (l) are bound to form an oriented fibre mat or corresponding knitted element, by means of which the fibres (1) are laminated inside resin or other binder and thus form a strong shell structure, characterized in that the reinforcing fibre (1) in the transverse direction is bound to the smooth knitted fabric formed by the right-side loops (2) by means of the wrong-side loops (3, 4).

10. A knitted fibre structure in accordance with Patent Claim 9, characterized in that the knitted fabric (5) is hose-like, in which the reinforcing fibres (1) run in a continuous spiral round the knitted fabric (5).

11. A knitted hose-like fibre structure in accordance with Patent Claim 10, characterized in that there is a narrow spiral strip (6) without reinforcing fibre (1) between the spirally circulating reinforcing fibres (1), by means of which the hose-like knitted fibre (5) can be cut open to form a ribbon.

12. A fibre structure in accordance with any of Patent Claims 1 - 11, characterized in that the reinforcing fibres, for example aramide fibres, have been coiled, so that the fibre structure is elastic also in the direction of the fibres.