Applicability of J-integral to tension-softening materials

This brief paper addresses the application of the J-integral to fracture analysis and toughness characterization of quasi-brittle materials, with specific focus on the tension-softening behavior in the fracture process zone. Concern is often raised on the validity of the J-integral when unloading occurs in the material points along which the J-integral contour path traverses, particularly during process-zone growth. This paper clarifies that this concern is misplaced. Whereas the J-integral contour wraps around the tension-softening line springs of the bridging elements in the process zone, the material points on the J-integral contour undergoes elastic loading and unloading. Therefore application of the J-integral to quasi-brittle materials does not violate the basic tenet of the assumption of nonlinear elastic material behavior underlying the J-integral theoretical formulation.