Punch shear performance and damage mechanisms of three-dimensional braided composite with different thicknesses

Abstract

In this study, the punch shear properties and damage mechanism of three-dimensional braided carbon/epoxy composites with different thicknesses are investigated both experimentally and numerically. Three kinds of specimen thickness are prepared: 3 mm, 5 mm, and 8 mm. A modified split Hopkinson pressure bar with a specially designed punch shear fixture are used to conduct the punch shear tests. The results indicate that the punch shear modulus increases along with the specimen thickness, whereas the peak punch stress shows insensitivity to the change in thickness. The specific energy absorption decreases with an increase in thickness due to a reduction in composite damage. Moreover, the dominant failure modes under punch shear loadings are discussed through SEM examinations and finite element analysis. The results show a high level of agreement between the experimental and finite element analysis models. Particularly, the finite element analysis model simulates the punch shear damage evolution at various high strain rates. Both the stress distribution and stress propagation process are also investigated in the model. It is found that a low-stress zone appeared in the punch region and the zone area decreases as the thickness increases.