Investigation of stiffness properties of PEEK in the transition region between Tg and Tm (Masterarbeit)

Abstract

This thesis investigates the stiffness properties of neat and carbon fiber reinforced PEEK in the temperature region between glass transition and melt. This regime is rarely studied comprehensively and quantitatively, but is fundamental for accurate material models for process simulation. Due to a lack of data in this regime, current material models rely on assumptions (e.g. absolute values of modulus above Tg, interaction between amorphous and crystalline regions) that remain to be proven. This research project combines Dynamic Mechanical Analysis (DMA) and rheology with crystallization kinetics from Differential Scanning Calorimetry (DSC), providing a unique data set and insights into the relation of stiffness properties to crystallinity and temperature histories. The results outline the necessary steps for improving existing material models. A revised crystallization model should include the influence of melting temperature on the induction time of crystallization for both neat and fiber reinforced PEEK. An experimental data driven model of the tensile modulus of neat PEEK is developed, addressing shortcomings of previous approaches and providing unique insight into the high temperature regime.