In-plane and interlayer shear strengths for needled composites prepared by different needling processes

The in-plane and interlayer shear properties of 3D needled composites are closely related to the complicated needling processes. The microstructure and fiber morphology of the needled composites are observed, and the in-plane and interlayer shear experiments of the needled composites with different needling processes are carried out. The failure modes of the composites in two different shear experiments are analyzed through the observation and analysis of multiple fractures. Based on the failure analysis of the microstructure, the strength prediction models are established by finite element method to calculate the shear strengths of the composites with different needling processes. The simulation results are in good agreement with the experimental results, where the maximum relative errors are 4.65 % and 14.52 % respectively. Moreover, the effects of different process parameters on the in-plane and interlayer shear strengths are demonstrated by the simulation models. This study can effectively guide the design for 3D needled composites with different needle punched processes.