Assessment of interface stress concentrations in layered composites with application to sandwich panels

Layered composites where one or more layers consist of an inhomogeneous material are subject to an increased delamination hazard compared to laminae consisting solely of homogeneous materials. This effect is caused by an incompatibility of the microscopic modes of deformation associated with the individual layers. In the present paper, two concepts for analysis and assessment of the delamination hazard induced by the deformation mode incompatibility are presented. The first concept is a microscale approach based on the analysis of local stress singularities. The second concept is defined on the mesoscale using the average energy release rate as a fracture parameter. Both concepts are derived and illustrated for the example of a structural sandwich panel with hexagonal honeycomb core. The study is closed with a discussion on the advantages and disadvantages of the different approaches.