A quantitative thermoelastic stress analysis method for pultruded composites

A non-contact Thermoelastic Stress Analysis (TSA) method is proposed to measure the sum of the direct strain components on the coated surface of thick pultruded composites. Traditionally, TSA methods are used to relate the change of surface temperature to the change of the first invariant of the stress. The proposed method takes advantage of the in-plane transversely isotropic surface layer and relates the measured temperature change to the sum of the surface strains because the latter are directly related to the first invariant of stress. Quantitative strain measurements using the TSA method are verified for multi-axial stress states by comparing the measured in-plane strain invariant in plate samples with a circular hole to those obtained from finite element (FE) simulations. Good comparisons are obtained when compared to the FE strain contours.