Thermal Fracture Toughness of a Bi-Material Layer

摘要

Fracture at the interface between dissimilar materials becomes an important issue in many bi-material layered systems, such as composites and micro-electronic devices. It is well known that there are large thermal expansion coefficient mismatches between the individual layers of the electronic assemblies. The mismatch can lead to large thermal stress at the interface resulting in thermal cracks during the operation. To avoid such failure in bi-layered structure, it is necessary to provide a simple and efficient analytical model, so that the stress level in the layers can be accurately estimated. Basing on the Bernoulli beam theory, a simple but accurate analytical formulation is derived for the calculation of the thermal stress and the strain energy release rate due to the thermal mismatch in bi-material layered structures. The analytical results are compared with finite element analysis results. The good agreement shows that the proposed approach is able to provide an efficient way for the calculation of strain energy release rate in bi-material layered structures. The effects of layer thickness and material property on the fracture toughness are presented through a parametric study.