Macro-scale fracture analysis of isothermal composites: Theory and seven applications

Starting with the macroscopic energy balance and the macroscopic entropy inequality, a lower bound is derived for the critical strain energy at which an isothermal composite or multiphase material fractures or fails. It relates the work done on the body, or the strain energy created in the body, to the new fracture surface area created. No assumption is made about the number or configurations of these fractures. Using previously published experimental observations by others, seven examples are developed to demonstrate how this inequality can be used to calculate bounds that can be compared with experimental observations. Six involve carbon fiber/epoxy aerospace laminates, and one an oil/gas producing sandstone. No adjustable parameters or history matching are employed.