Co-authors​ :

 Tao TAO ZHENG (CHINA), Licheng GUO (CHINA), Tao TAO ZHENG (CHINA) 

3D woven composites have been commonly adopted for lightweight applications in aerospace, astronautics and defense fields because of their exceptional energy absorption, better damage tolerance and lower fabrication costs compared with conventional laminated composites. However, the complex interlaced yarn architecture makes the failure behaviors of 3D woven composites especially complicated. In the literatures, most of the damage models of 3D woven composites are mainly aimed at the mesoscale, ignoring the microstructure of the fiber filaments and matrix inside the fiber yarns. Moreover, conventional mesoscopic models require a large number of input parameters, such as failure strength and fracture toughness of yarns in each principal direction, which are usually difficult to accurately obtained through experiments. Therefore, highly accurate and efficient damage prediction models are necessary to deeply study the damage mechanisms of 3D woven composites under complex loads.
In this paper, a multiscale damage model is proposed based on a micro-mesoscale bridging model and a multiscale kinking model, which can predict the damage development processes of 3D woven composites under different loading conditions using only few material parameters. The correlation between the mesoscopic stress of yarns and microscopic stress of constituents is established by employing a stress amplification factor. With the microscopic stresses, the fiber breakage and matrix failure can be separately judged at the microscale. Therefore, at the microscale, the various mesoscopic damage modes of yarns, including tensile fiber breakage, compressive fiber kinking and transverse inter-fiber fracture, can be simply divided into matrix- and fiber-dominated damage. For the special-shaped structures of 3D woven composites, a novel full-scale geometry modeling method, capable of characterizing the complex geometric features of fiber yarns, automatically defining the local material orientation, and appliable to special-shaped structures, is developed to reconstruct the biaxial specimens of 3D woven composites. Then, the multiscale modeling of 3D woven composites is established, including hexagonal microscopic RVC, full-thickness mesoscopic RVC, and full-scale model of cruciform specimens. Instead of using deterministic values, the stochastic strengths of fiber filaments are characterized by adopting a Weibull probabilistic distribution. The proposed multiscale damage model is integrated to ABAQUS with a user-defined subroutine to analyze the tensile, compressive and biaxial tensile failure behaviors and damage mechanisms of 3D woven composites. The numerical predictions exhibit good correlations with the relevant experiments.