Experimental and numerical investigation of shear-driven fracture in hybrid tape/fabric-laminate end-loaded-split specimens

Crack migration in polymer matrix composites is a commonly observed process in which delamination transitions into intralaminar fracture due to ply-level shear loading. To date, several studies have attempted to reproduce this failure process in an experimental setting; however, most efforts have found crack migration difficult to control, resulting in variability in the observed damage morphology and the associated specimen response. The objective of this work is to develop a new experiment that enables direct control of crack migration based on the end-loaded split (ELS) test configuration and a custom dual-actuator load frame. A non-standard hybrid ELS specimen geometry was used, containing a core of 90° tape plies placed at the specimen’s midplane and bounded by plain-weave fabric plies. The fabric plies were used to constrain the crack migration process to the core plies and to stabilize the pre- and post-migration delamination growth at the tape/fabric interface. The crack migration process in the specimens was controlled by changing the direction of the ELS loading, which alters the sign of the local shear stress that drives fracture. Experimental tests were performed to initiate repeatable and controllable single migrations and multiple consecutive migrations. The experiments were simulated using the BSAM progressive damage analysis tool, demonstrating good agreement between the experimental and numerically derived global force–displacement responses, the locations of major migration events, and the delamination growth rate. Differences in the observed and simulated fracture patterns are analyzed and discussed to inform future developments of the experimental and computational methods described herein.