Novel thermomechanical characterization for shrinkage evolution of unidirectional semi-crystalline thermoplastic prepregs (PPS/CF) in melt, rubbery and glassy states

Abstract

Shrinkages, distortions and high residual stresses in the thermoplastic composite parts are induced due to high processing temperature, anisotropy, and fiber–matrix shrinkage mismatch. In this paper the shrinkages have been investigated experimentally and modeled by thermo-mechanical constitutive equations for PolyPhenylene Sulfide (PPS) and the unidirectional Carbon Fiber (PPS/CF) composite prepreg. The thermal shrinkage and the crystallization shrinkage were retrieved from Thermal Mechanical Analysis and compared to a Pressure specific volume Temperature diagram. To describe the crystallization shrinkage in the cooling process accurately, the crystallization kinetics of PPS was evaluated using Differential Scanning Calorimetry. The temperature-dependent elastic modulus was measured by a shear rheometer to formulate a new constitutive model. The mathematical model for shrinkage was validated by a press consolidated [0]₁₂ laminate and unbalanced laminates in four lay-ups. The thermo-mechanical model results presented here provide significant rules for the thermomechanical and shrinkage predictions for the industrial applications of thermoplastic composite.