Measurement of Residual Stresses in Fiber Reinforced Composites Based on X-Ray Diffraction

1. ABSTRACT X-ray diffraction (XRD) measurements have been made to determine residual stresses in embedded Al particles placed between the first and second ply of both unidirectional and fabric graphite/PMR-15 composite specimens. In order to further verify the results obtained, the effect of externally applied four-point bending on the measured strains and stresses in the Al inclusions was investigated. In the modeling part of this research, the state of stress in these inclusions was calculated using visco-elastic laminated plate theory and the Eshelby method. The numerical solutions for different concentrations of inclusions were subsequently compared with the experimental results. It has been shown that the thermal residual stresses in graphite/polyimide composites can be determined with reasonable accuracy by using X-ray diffraction from embedded inclusions in conjunction with the application of the Eshelby method.