Strain fields at an interface crack in a sandwich composite

Interface damage characterization and interlaminar failure of sandwich specimens with an initial interlaminar delamination in between the face sheet and the core is done by using the digital image correlation method (DIC). Virtual strain gages are emulated at the interface and beneath it, in the polyurethane core and opening strains are measured. Peel tests reveal interesting particularities on damage localization and strain variation while damage is completed. After analyzing the experimentally obtained results, four characteristic domains which describe the opening strain variations in the core are established together with the corresponding variation of the opening strain at the interface. The critical strain at damage initiation, as well as the critical displacement when damage is finalized, is established by DIC in the cohesive zone. After the calibration of the finite element model through experimental results, the use of the cohesive elements together with a linear softening law give in the core a pattern of strain variation similar to the one obtained experimentally.

► Interface damage and failure are analyzed by using digital image correlation.
► Four characteristic domains of opening strain variations in the core are presented.
► Critical parameters for initiation and finalization of damage are established.
► Cohesive finite elements give a strain variation similar to the experimental one.