Study On The Microstructure And Mechanic Properties Of The Three-Dimension Braided Complex Composite

With the application of three-dimension(3D)braided composites, more and more studies on it have been done. Most of the studies on3D braided composites have been concentrated on those with simple rectangle cross-section. Few on complex rectangular cross-section has been published. The complex rectangular shape here refers to the kind of the geometrical shape formed by joining two or more rectangles together, such as T-shape, L-shape, etc. In this paper two braiding methods including the right-angle braiding method and the rounding chamfer braiding method are applied to manufacture the complex preforms with L-shape. The yarns paths show that in the joint region there exhibits three different kinds of unit cells, including the interior unit cell, surface unit cell and corner unit cell. The yarns tracks are same for the complex preform with rounding chamfer.The purposes of this paper are as follows:(1)We analyze the four-step braiding method according to the yarns paths to know the unit cells in the preform, including the interior unit cell, surface unit cell and corner unit cell. The relationship between the braiding parameters and the dimension of the preform is analyzed.(2) The braidings are cured with the certain process. The yarn volume fraction is calculated with two methods, namely the volume method and density method. The result from the later one is more accurate. (3) To do research how the structure of the joint region influences the mechanic properties, experiments are taken to compare the specimen mentioned above. The experiment focuses on the corner region of the composites. The composite formed by the traditional method performs best among them due to the structure integrity and the more yarns in the interior unit cell of the joint region.