Correction method for evaluation of interfacial fracture toughness of DCB, ENF and MMB specimens with residual thermal stresses

The energy release rates associated with crack growth in multilayered double cantilever beam (DCB), three-point end notched flexure (ENF), and mixed-mode bending (MMB) specimens, including the effects of residual thermal stresses, are derived as special cases of Nairn’s formulation [Nairn JA. On the calculation of energy release rates for cracked laminates with residual stresses. Int J Fract 2006;139:267–93]. The difference between the true toughness and apparent toughness attributable to the consequence of ignoring residual stresses can be calculated for a given specimen geometry and mechanical properties based on classical lamination theory. The true fracture toughness is obtainable using the apparent fracture toughness and the present correction method. Numerical examples of DCB, ENF, and MMB tests are presented, and the calculated difference in the energy release rates based on the present correction method is compared to those obtained using FEM to verify the correction method.