X-Ray Diffraction Investigation of Triaxial Residual Stresses in Composite Materials

Triaxial residual strains have been measured in a thermosetting resin of the type used in high performance fibre composite materials. X-ray diffraction measure ments were made on fine metal particles accurately positioned within the material. The variation of stresses and strains with the cure temperature and the amount of particulate matter present were investigated. No significant differences were seen in measured strains over a range of metallic particle volume fractions. However, the expected trend of increas ing compressive strains with increasing cure temperatures was not seen and the magni tudes did not coincide with theoretically predicted values. These results are discussed and some explanations are offered to describe the behaviour observed.