AU3037497A

AU3037497A - Composite material tubular equipment produced by winding of weft-unbalanced wov en fabric on a compressible mandrel

Info

Publication number: AU3037497A
Application number: AU30374/97A
Authority: AU
Inventors: Bernard Castagner
Original assignee: Individual
Current assignee: Individual
Priority date: 1996-05-23
Filing date: 1997-05-23
Publication date: 1997-12-09
Also published as: CA2255860A1; PL330186A1; CN1219903A; FR2748964B1; FR2748964A1; WO1997044181A1; JP2000510779A; TR199802381T2; BR9709357A; KR20000015809A; EP0907494A1; NO985411L; NO985411D0

Description

1 TUBULAR ELEMENTS IN COMPOSITE MATERIALS OBTAINED BY WINDING AN UNBALANCED-WEAVE FABRIC ON A COMPRESSIBLE MANDREL 5 Numerous structural elements, in particular piles, posts or masts, are made from steel and, as a consequence, suffer from disadvantages such as: a) their significant weight and, in certain cases, the resultant problems in placing them; 10 b) their tendency to corrode due to the effects of air, water or the soil. c) the cost of their maintenance. In an attempt to overcome these disadvantages, such structural elements have been made from aluminium or 15 composite materials. Regarding such structural elements in composite materials, the technique that is generally employed consists in winding filaments of rovings. Structural elements such as piles, posts or masts should not only have good breaking strength characteristics but also 20 be highly rigid when subject to movements which tend to bend them. To achieve this, it is necessarily for the composite structure to take full advantage, firstly, of the tensile breaking and compressional strength of the fibers and, secondly, of the flexural modulus of the reinforcing fibers. 25 Thus, the major portion of the latter should be placed along the axis of the pile, post or mast. According to the invention, elongated structures such as piles, posts, masts, beams, are produced by winding, preferably helically, thermosetting-resin-impregnated glass 30 fabric impregnated with a a heat-setting resin such as an epoxy, polyester, or vinyl ester resin. According to the invention, these fabrics have an unbalanced weave, in other words have a higher percentage of filaments in the fill or woof than in the warp. Additionally, 35 their weave makes angular deformability possible thereby 4600\14606US.DOC - 13 novembre 1998- in/ 2 making it possible, according to the invention, to place the fill or woof filaments parallel to the X- X' axis of the structure. The originality of the design of these high bending 5 strength composite tubes of the invention will become clear from the description and corresponding technical justification. According to the invention, a tube is produced by helically winding a glass fabric in which the ratio warp/woof 10 is unbalanced, with c>t, where c is the percentage of the fiber placed in the warp and t is the percentage of fiber placed in the woof. The preferred values are between 10 and 25% for c and between 90 and 75% for t; this figure for modularity makes it possible, as a function of 15 diameter/thickness ratio, to ensure good resistance against radial buckling. According to the invention, the tube is built up from successive layers provided by forward and return helical winding. On the forward runs, helical winding is done at an 20 angle of B1 = (90 0 - ) with respect to the longitudinal axis and on the return run with an angle of B2 = (900 + a). According to the invention, helical winding is preferably carried out while giving the fabric an oblique slope of angle a (see FIG 1) so that the fill or woof 1 is parallel to the 25 longitudinal axis of the tube, the warp 2 having an angle a with respect to the circumferential plane 3; this arrangement improves flexural modulus. According to the invention, each layer is wound preferably by partially overlapping (see 6) successive turns 30 4, 5 (see FIG 2) . To avoid local excess thickness the width of offset 1 between two successive turns is such that L 35 n 4600\14606US.DOC - 13 novembre 1998 -2/7 3 where L is the width of the layer and n is an integer > 1. Without departing from the invention, helically winding is performed either with individual widths abuting as 5 indicated by reference 7 in FIG 3, or with alternating individual widths (see FIG 4). The individual widths 8 and 9 are placed during the first outward run. The individual widths 10 and 11 are placed during the first return run; the widths 12 and 13 during the second outward run. This latter 10 type of winding improves resistance to inter-layer shear stress. According to the invention, where winding is done with the turns abuting, the successive layers are preferably offset in order to decrease the effect of discontinuity 15 brought about by the individual widths. For example, in the case of a helical winding with abuting individual widths of width L and a number of layers q, the position of each layer (outward + return run) is offset by a space of width K such that 20 L K = m 25 where m is an integer > 1 and if possible with q m = r 30 r being an integer (see FIG 5). The individual widths 14 ,15, 16 are the widths for the first outward run and the individual widths 17,18 and 19 are the widths for the second outward run. 35 Even though the preferred fabric is a glass fabric it is possible, without a departing from the scope of the invention, to employ fabrics in carbon, aramide, or high 4600\14606US.DOC - 13 novembre 1998 - 3/7 4 strength polyethylene. It is also possible to employ hybrid fabrics, for example glass plus carbon. Without departing from the invention, the fabrics can be pre-impregnated with heat-setting resin. 5 Without departing from the invention, the fabrics employed can be pre-impregnated with thermoplastic resin. Without departing from the invention, the fabrics can be wound at the same time as a thermoplastic film and impregnated by melting plus compression. 10 Where it is desired to produce structural elements such as piles, posts or masts which are of considerable thickness, including cylindrical portions and having an unbalanced fiber reinforcement along the X-X' axis of the structural element, the presence of significant forces tending to clamp the 15 composite structure against the mandrel, after polymerization, has been observed; this phenomenon can make it difficult to remove the element from the mandrel and can create micro-cracking in the structure. In order to avoid these major disadvantages, according to 20 the invention, a smooth layer of a compressible material is placed on the mandrel after which the glass fabric is wound onto this compressible mandrel. According to the invention, the characteristics of compressability of the material will be such that it only 25 shows a slight deformability under the limited force of winding the fabric and it will absorb the contraction of the composite structure and only transmit a slight clamping force to the mandrel, thereby facilitating removal therefrom. The material chosen should have a low coefficient of friction. 30 According to the invention, the material is preferably a closed-cell polyethylene foam with a smooth polished skin. Without departing from the invention, another material having the above characteristics can be used, for example a flexible polyurethane foam. 4600\14606US.DOC - 13 novembre 1998 -4/7 5 According to the invention, in order to facilitate removal from the mandrel and preserve the internal surface state of the tube, the foam should be coated with a terpane film. 5 In the presence of flexural forces operating in a priviledged radial direction, oblong-shaped tubes are provided (see FIG 6) . This type of tube can for example be employed in the construction of breakwaters. Without departing from the invention, the tube can have a 10 sandwich structure (see FIG 7) constituted by two concentric tubes 20, 21 obtained by means of the invention and separated .: by a wall 22 in a material which is rigid in compression such as a rigid foam, a honeycomb structure, balsa, and so on. *** This makes it possible to make the tubes lighter and improves .15 rigidity. -0 Without departing from the invention, in order to improve 00 rigidity in the presence of bending forces acting along a preferred axis, the inner tube can be cylindrical and the outer tube oblong. 0 0 0O *0 0 S 0e 0 :0 4600\14606US.DOC - 13 novembre 1998 -5/7

Claims

1.- A tube in a composite material characterised in that it is obtained by helically winding fabric in which the fill 5 or woof is unbalanced with respect to the warp

2.- The tube according to claim 1, characterised in that it is provided by inclining the fabric by an angle equal to the angle of helical winding. 10

3. - The tube according to one or several of claims 1 and .... 2, characterised in that the helical winding of the tube is performed with partial overlapping of successive turns. .15 4.- The tube according to one or several of claims 1 and 2, characterised in that individual widths are butt-jointed or alternate and successive layers thereof are offset in order to counterbalance discontinuities due to the individual widths. 20 **. 5.- The tube according to any one of the preceding claims, characterised in that the fabric employed is composed of fibers of a single type or of hybrid fibers. :25 6. - The tube according to any one of the preceding claims, characterised in that its profile is cylindrical or * 0 oblong. 0

7.- The tube according to any one of the preceding 30 claims, characterised in that it has a single-walled structure.

8.- The tube according to any one of the preceding claims, characterised in that it has a sandwich structure 4600\14606US.DOC - 13 november 1998 -6/7 7 that includes a material having high compression strength between two tubes.

9. - The tube according to any one of the above claims, 5 characterised in that its winding mandrel is covered with a layer of compressible material.

10. The tube according to claim 9, characterised in that the compressible material is a closed cell polyethylene foam. *. 0\ 14 0166S O 3n~ m19 -/