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免费下载此文档侵权投诉Structure Design of the 3-D Braided Composite 261 In comparing with two dimensional composite laminates, a key property of the new innovative 3-D braided composite is its ability to reinforced composites in the thickness direction. Braiding with continuous fibres or yarns can place 3-D rein-forcements in monocoque structural composites, it includes multi-directional fibre bundle which interconnect layers. Since the braiding procedure dictates the yarn structure in the preform and the yarn structure dictates the properties of the compos-ite, designing the braiding procedure to yield the desired structural shape that is endowed with the desired properties is an important element in textile composite technology [3]. Thus, it is feasible to design the textile structural composites with considerable flexibility in performance based upon a wide variety of preform geome-tries and structure parameter.

The ant colony optimization (ACO) algorithm is a novel simulated ecosystem evo-lutionary algorithm. It takes inspiration from the observations of ant colonies foraging behavior with which ants can find the shortest paths from food sources to their nest [4]. Preliminary study has shown that the ant colony algorithm is very robust and has great abilities in searching better solutions. ACO algorithm has been successfully used to solve many problems of practical significance including the Quadratic As-signment Problem [5], Traveling Salesman Problem [6], Single Machine Total Weighted Tardiness Problem [7].

Whereas wide application of hollow-rectangular-section 3-D braided composite in engineering, the 3-D braided composite made by 4-step method is taken as the studied object in this paper. The 3-D braided composite description is given in section 2. The stiffness and damping analysis of the composite were introduced in Section 3. And model of structure optimization designs for the composite were proposed. A hybrid algorithm based on ACO algorithm for solving the optimization problem is presented in section 4. Simulation results and the discussion of the results are presented in sec-tion 5. Finally, conclusions are given in Section 6.

2 3-D Braided Composite Description

The 3-D braided fibre construction is produced by a braiding technique which inter-laces and orients the yarns by an orthogonal shedding motion, followed by a compact-ing motion in the braided direction. The basic fibre structure of 4-step 3-D braided composite is four-direction texture. An idealized unit cell structure is constructed based upon the fibre bundles oriented in four body diagonal directions in a rectangular parallelepiped which is shown schematically in Fig.1 [8][9]. The yarn orientation angles αand βare so-called braided angle. From the geometry of a unit cell associ-ated with particular fibre architecture, different systems of yarn can identified whose fibre orientations are defined by their respective interior angle αand cross sectional angleβ, as previously show in Fig.1. According to requirement of braid technology, the range of αand βare commonly between 20°and 60°. In Fig.1, geometric parame-ters of cross section of composite are b1, b2, h1, and h2 respectively.

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