Bridging and toughening of short fibers in SMC and parametric optimum

A simple analytical approach was proposed to simulate the bridging and toughening of randomly oriented short fibers in brittle matrix. Based on a magnitude order analysis, the energy dissipation before fiber pullout was neglected. The coupling of matrix spalling and fiber pullout was simulated by an approximate bridging model to determine the energy dissipation in the whole pull-out process of randomly oriented short fibers in brittle matrix. The proposed approach was applied to analyze the bridging/toughening of short fibers in SMC plates with mode I crack and to discuss the effects and optimum of parameters. The modelling results show that the main parameters for toughening are fiber length and interface friction stress and there is an optimal combination, i.e., their product nearly equals a constant (about 15–17 MPa-mm).