In view of the fundamental uses of composite materials for in-plane loading and the needs to combat delamination due to accidental out-of-plane loading, quasi-three-dimensional (Q3D) woven composites have been developed in this study. The Q3D woven composites are not three-dimensional woven composites because there is no fiber specifically oriented in the thickness direction. However, the Q3D woven composites are similar to three-dimensional woven composites because all in-plane fibers between adjacent layers are interlocked together to form an overall three-dimensional network. Accordingly, the Q3D woven composites should offer high delamination resistance similar to the three-dimensional woven composites while retain reasonable fiber flatness, and hence high in-plane properties. In justifying the advantages of the Q3D woven composites, several variations of Q3D woven composites are presented. The comparisons of their in-plane stiffness and buckling strength with the laminated and two-dimensional and three-dimensional woven counterparts are performed with the use of compression tests. Moreover, the damage patterns due to low-velocity impact and the residual properties of the impacted specimens are characterized by using the compression after impact (CAI) tests. Experimental results have concluded that the innovative Q3D woven composites with five-harness have similar in-plane stiffness to the laminated composites but have higher damage tolerance than the laminated counterparts.
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