A new interpretation of mode I interlaminar fracture in layered materials

Interlaminar crack propagation in layered materials, such as composites, is still a not fully understood phenomenon in fracture mechanics. Experimental observations reveal a broad spectrum of crack propagation velocities during the interlaminar fracture of layered materials under varying loading conditions and rates. While there have been numerous studies examining interlaminar crack propagation under quasi-static, fatigue, and more recently, high-speed loading, there has been a notable lack of endeavors to present and interpret crack growth data within a unified framework. To this direction, we present a new interpretation of interlaminar crack propagation data acquired from a broad test campaign under various mode-I loading conditions (quasi-static, fatigue and high-speed). We connect the crack tip velocity to the rate of change of the SERR to propose a new equation/model that shows potential in presenting and explaining the variety of experimental crack growth data. This correlation arises from a simple mathematical analysis of the rate of change of the SERR using the chain differentiation rule. Subsequently, it is further substantiated by experimental evidence, in an effort to accommodate results from various experiments under a unified description. A robust correlation of the test data is established through a range of slopes which are proven -experimentally- to be characteristic constants of the mode-I interlaminar fracture of a specific material system.