Thermoformed Glass Fiber Reinforced Polypropylene: Microstructure, Mechanical Properties and Residual Stresses

摘要

The objective of this work was to characterize the microstructure, mechanical properties and residual stresses in glass fiber reinforced PP composites with respect to the thermoformingparameters (temperature, pressure, residence time and cooling rate) and as a function of the fiber-matrix interface quality. First, DSC technique was used to investigate the crystallization behavior of the PP matrix. Second, short beam shear tests and tensile tests in the +-45deg directions have been conducted to characterize the interface strength. Finally, residual stresses were measured via the curvatures of unsymmetric cross-plied laminates. The cooling rate was found to be a critical parameter since the matrix crystallization temperature, the interfacial strength as well as the residual stresses showed large variations with various cooling rates. At slow cooling, the crystallization process initiates at higher temperatures and covers longer time periods resulting in more spherulitical matrix structures.