A Novel Test Geometry for Characterization of Traction-Separation Behaviour in Composite Laminates Under Mode I Delamination

Abstract

The integration of composite laminates into automotive structures can provide weight reduction and improvement in occupant safety. However, the adoption of such materials requires characterization and efficient modeling of the damage behaviors of composite laminates which may occur during crash events, such as delamination. Numerical modeling techniques such as cohesive zone modeling require a traction-separation response for each mode of loading. The standard test technique used to characterize Mode I delamination, the double cantilever beam (DCB), measures the critical energy release rate; however, additional tests or inverse fitting techniques are required to characterize the full traction-separation response. Additionally, compliance inherent in the DCB specimen can influence the measured energy release rate while the large size of the specimen complicates the high deformation rate testing needed for crash analysis. In this study, a novel Mode I test specimen adapted from a recent advancement in structural adhesive characterization is applied to evaluate composite delamination. The hybrid Rigid Double Cantilever Beam (RDCB) test specimen presented herein consists of rigid steel adherends co-molded to a composite plate containing a crack initiator. The use of steel adherends eliminates compliance in the composite laminate and ensures the interface of interest is loaded consistently and uniformly during tests, enabling measurement of the Mode I traction-separation behavior of composite delamination in a single test. As an example, the hybrid RDCB geometry is used to characterize the Mode I delamination behavior of a unidirectional E-glass fiber/epoxy laminate under quasi-static conditions, highlighting the ability of this specimen geometry to extract a full traction-separation behavior from a single test.