Damage propagation in short fiber thermoplastic composites analyzed through coupled 3D experiments and simulations

Abstract Due to the complex nature of the heterogeneous microstructures of short fiber composites, computationally predicting their mechanical behavior, especially past the elastic regime and into the damage initiation and progression regimes, is very challenging. Matrix cracking has notably been difficult to predict because it can propagate in different manners, such as fiber mediated interfacial cracking and conoidal cracking, which have not been well understood. Therefore, this work couples in-situ X-ray micro tomography experiments with a finite element simulation of the exact microstructure to enable a sub-fiber 3D microstructural study by tracking damage propagation and computing the local stresses and strains in the microstructure. Here we show the role of shear stress in interfacial cracking (and how it differs from debonding), the role of hydrostatic stress in conoidal cracking, and the role of environmental damage in longitudinal fiber breakage. In doing so, this work gives insight into the stress states resulting in non-linear damage propagation in thermoplastic fiber composites.