Use of diffuse approximation on DIC for early damage detection in 3D carbon/epoxy composites

This work is part of a global experimental approach aiming at studying the damage and rupture of 3D carbon/epoxy composites and based on multiinstrumented experiments. It focuses on the use of digital image correlation (DIC) in order to detect the development of local non-linearities corresponding to damage (with no other non-linearities) and is limited to small deformation. To that purpose, the strain field is required, hence derived from the measured displacement field, through a diffuse approximation algorithm. This approach is detailed and studied in terms of filtering and some criteria are proposed to choose the filtering parameters. A pragmatic approach based on the evolution of the linear approximation of the strain is proposed in order to detect local non-linearities leading to a local damage indicator. The effect of the filtering on the damage detection is then discussed.