Effects of braiding architectures on damage resistance and damage tolerance behaviors of 3D braided composites

The primary goal of this research is to present a systematic study on the damage resistance and damage tolerance behavior of three-dimensional (3D) braided composites. Therefore, the low velocity impact (LVI) and compression after impact (CAI) tests of 3D braided composites with eight different braiding architectures and a traditional two-dimensional (2D) laminated composite were carried out. The transient impact force response demonstrates that for 3D braided composites, fiber and matrix work as a whole to withstand impact loads and exhibit a progressive failure process, which is a very different phenomenon from the 2D laminates. The damage morphologies of 3D braided composites are obviously different, for 3D four-directional and 3D five-directional composites the damage patterns are in fusiform shape, and in the case of 3D six-directional and 3D seven-directional braided composites, damage patterns exhibit cross-shape. The energy absorption rates of 3D braided composites are 3.53–7.6% lower than 2D laminate, which means less impact energy has been dissipated by matrix and fiber damage. The comparison of LVI damage parameters and CAI shows that 3D5d-A has better damage resistance and damage tolerance.