Experimental investigation of composite patches with a full-field measurement method

The aim of this work is to study the displacement and strain fields on the surface of a composite patch used to reinforce metallic structures. The analysis focuses on the stress evaluation in both the composite and the adhesive. Shear stress concentrations exist in particular in the adhesive because of the progressive load transfer from the substrate to the patch along the so-called transfer length. The grid method is used for this purpose. Analysis of uniaxial tensile tests shows progressive load transfers in the longitudinal direction and also in the transverse direction, the latter due to Poisson's ratios. Complex couplings between longitudinal and transverse directions are also observed near the free edges of the patch. Bidimensional phenomena are compared to results obtained from a usual unidimensional theoretical approach.