Visualization of Fiber/Matrix Interfacial Shear Debonding Mechanism at High Rate Loading

Abstract

The interfacial properties of fiber reinforced composites are widely studied due to their importance in controlling the desired material strength. However, the effects of loading rates on interfacial crack initiation and propagation at the interfaces are yet to be studied systematically. Thus, visualization of the debonding event in real time facilitates the study on the dynamic crack initiation and propagation mechanisms at the fiber-matrix interface. In this study, the debonding between the fiber and the matrix is recorded by synchronizing a modified tension Kolsky bar with high-speed synchrotron X-ray phase contrast imaging (PCI) technique. The microbond and pullout methods were utilized to study the interfacial shear debonding mechanism of S-2 glass fiber and carbon fiber composite Z-pin with SC-15 epoxy at pull-out velocities of 2.5 and 5.0 m/s. Both S-2 glass fiber and Z-pin at 2.5 and 5.0 m/s experienced a catastrophic interfacial debonding. Z-pins revealed relatively high peak debonding forces compared to S-2 glass fiber at both velocities. Furthermore, the peak debonding forces for both materials were higher for higher velocity.