Experimental evaluation of through-the-thickness stress distribution in transverse crack tension test samples

Transverse Crack Tension (TCT) samples represent an alternative to End Notched Flexure configurations for the characterization of pure mode II fracture toughness of Fibre Reinforced Polymer composites. TCT is supposed to reproduce a pure Mode II failure mechanism while avoiding the frictional energy dissipation between the flanks of a starter crack. The TCT geometry is that of a unidirectional tensile sample where a number of embedded plies, centered on the middle plane, are cut in the transverse fibres direction. The tensile loading should then activate four symmetric fronts of mode II delamination from the transverse cut tips. The present work describes the implementation of two full field experimental stress analysis techniques: Thermoelastic Stress Analysis (TSA) and a Digital Image Correlation (DIC). These are applied to evaluate the stresses and strains on the through-the-thickness surface of a TCT sample during static and cyclic loading. The stress and strain information carried out by the thermoelastic signal and DIC analysis are analyzed to investigate the effectiveness of the TCT specimen for the purposes of Mode II characterization.