Effect of the micro-structure on the compressive failure behavior of three-dimensional orthogonal woven composites

The failure behavior of three-dimensional orthogonal woven composites (3DOWCs) under in-plane axial compression has been experimentally and numerically investigated. The micro-structure at the intersecting points of the fabric reinforcement, which is induced by the tow force in the weaving process, is introduced. The strength and the induced damage along the warp and weft directions were investigated. The micro-structure of the 3DOWC including the details of the tow waviness and resin distribution was accurately obtained through a multiscale modeling approach. Resin cracking and the local stress concentration were captured by the numerical models, and they showed good correlations with the experimental results. The fiber undulation in the region of the tow intersection concentrated stress, which led to fiber fracture in the compression process. The main load-carrying tow, namely, the warp and weft tow along each direction, had different forms of undulation, which should be the reason for the decreasing compression-carrying capacity of the 3DOWC. With increasing Z-binder tow force, the level of fiber straightness decreased and the failure mode transformed from macroscopic brooming type to fiber microbucking. The inclination angle of the through-thickness fracture path suggested that fracture was induced by the shear failure in the load-carrying tows.