Thermal de-consolidation of thermoplastic matrix composites—I. Growth of voids

Thermoplastic matrix composites have one unique advantage, being reprocessable or recycleable through post-thermoforming and fusion bonding subject to a re-heating/cooling cycle. However, this advantage is not unconditionally available, and thermoplastic matrix composites may suffer greatly from unexpected deterioration in meso-structures during the thermal processing, leading to de-consolidation. Based on experimental observations, the mechanisms of thermal de-consolidation are discussed in detail, and a void growth model is established to evaluate the degree of de-consolidation in a post-thermal operation. Using this model the dependence of void growth on material properties and processing parameters, such as the compressibility of fibre reinforcement, the effects of elasticity/viscosity of matrix, the applied external pressure and processing temperature is evaluated. It is shown that the results obtained are in a good agreement with the experimental data.