In-Situ Observation of Thermal Residual Strains in Carbon/Thermoplastic Microcomposites Using Raman Spectroscopy

Thermal residual strains in carbon/thermoplastic microcomposites have been measured in-situ using micro Raman spectroscopy. This experimental method provides quantitative information of the relation between the level of residual strains and the temperature history. Two different microcomposites have been investigated; carbon fibre/ polycarbonate and carbon fibre/polypropylene. The observed strain-temperature profile exhibits two characteristic nonlinear zones for both composite systems. It is shown that the linear thermoelastic solution strongly overestimates residual thermal strains. In order to overcome this deficiency the thermorheologically simple model is applied to predict residual strains. The results indicate that the model correctly estimates the level of residual strains in thermoplastic microcomposites, but fails to describe the two nonlinear characteristic zones. This leads to the conclusion that a more complex constitutive model of the matrix phase must be considered.