Experimental And Numerical Investigation On Three-Point Bending Behaviors Of Unidirectional Warp-Knitted Composites

This study develops a novel specimen model, which considers the progressive damage of the layers, the knitting yarns, and the interlaminar cohesive zone, to investigate the flexural properties and the interlaminar shear properties of the unidirectional warp-knitted composites. Three-point bending tests are conducted as verification of the numerical model. Improved strain-based Hashin criteria are proposed to analyze the shear nonlinearity. Results show that specimens with small span-to-thickness ratios exhibit obvious nonlinear behaviors and the corresponding simulation results are sensitive to the value of the shear nonlinear factor. Failure mechanism and stress distributions are analyzed based on numerical simulations. The effect of the specimen size on bending behaviors is discussed. The influence of the width is found to be negligible but that of the span-to-thickness ratio is significant. The ranges of the span-to-thickness ratio corresponding to different failure modes are given. (c) 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 136, 48132.