Three-Dimensional Investigation of Free-Edge Effects in Laminate Composites Using X-ray Tomography and Digital Volume Correlation

Laminate composite materials are widely used for many industrial applications because of their high specific mechanical properties as well as the possibility to adapt the structure properties to its application and loading conditions by optimization of the stacking sequence. It is now well known that the mechanical properties mismatch of adjacent layers having different fibre orientation induces stresses concentrations at interlaminar interfaces in the vicinity of structure edges. Edge effects experimental investigation is generally made through two dimensional measurements, crack initiation detection and characterization using various observation techniques. In this paper, it is proposed to investigate edge effects by coupling 2D and 3D measurements, using X-Ray tomography and kinematic field measurements. A preconditioned Digital Volume Correlation is developped in order to capture the in depth evolution of the residual displacement discontinuity at the ply interfaces. After it has been validated by comparison with the 2D measurements on the surface, the analysis of the 3D fields is carried out.