Study of surface and sub-surface damage initiation and propagation in carbon/epoxy composites

The objective of this study is to create a link between defects detected through nondestructive testing (NDT) and the mechanical performance of the composite structures using strain mapping technique. Flash Thermography, a conventional NDT technique, is used to predict detectable pre-existing surface and sub-surface irregularities and defects on stitch-bonded biaxial composite laminates. Attention is drawn to the homogenized mechanical behavior at the macro-scale and to damage initiation and propagation at the unit cell level. Damage onset and propagation are studied using time-dependent nonlinear regression of the strain field. Effects of the manufacturing and installation irregularities on damage initiation, propagation, and failure are monitored at the end of the loading process.