Interfacial fracture mechanics on sandwich specimens with variable layer thickness

In this paper the influence of an elastic interlayer on the mechanical performance of an otherwise brittle material is analyzed in terms of interface stress intensity factors and crack tip loading mode. Dundurs' parameters are applied in order to characterize the elastic heterogeneity of the systems under investigation. It is found that critical interlayer thicknesses exist below which the second interface interacts with the near tip stress field of the interface crack. This critical thickness is different for thermal loading, d c res / w = 1.25, and mechanical loading, d c app / w = 0.75, where w is the width of the specimen. Crack tip stress intensities as well as mode mixities as a function of elastic mismatch and layer thickness deviate stronger from the respective bimaterial cases under thermal loading compared to mechanical loading. Stress intensity peak values are observed around d / w = 0.5 with respect to thermal loading.