Stress Measurement in Graphite/Epoxy Composites By X-Ray Diffraction from Fillers

Abstract

The purpose of this work was to measure stresses in graphite/epoxy composites by diffracting X-rays from crystalline filler particles embedded in unidirectional laminates before curing. Particles used were Ag, Nb and CdO, having sharp diffraction peaks at large diffraction angles, θ. The diffraction peaks shift linearly with applied stress in the fiber direction and have stress sensitivities of (2.6, 3.9 and 1.9) X 10 -4 deg 2θ/MPa for Ag, Nb and CdO respectively. Elastic strains in filler particles measured by X-rays are proportional to the corresponding composite strains in agreement with the model of H. T. Hahn. Residual strains and stresses in filler particles were also obtained.