Bag Bernard Schrauwen

Predicting the Yield Stress of Polymer Glasses Directly from Processing Conditions: Application to Miscible Systems

Abstract A previously developed model which predicts the yield stress of a polymer glass directly from processing conditions is applied to a system of miscible polymers. The selected system consists of a blend of polycarbonate with polyester and three blend compositions of increasing weight percentages polyester are investigated with respect to their aging kinetics. Based on these kinetics, the yield stress as it results form the thermal history experienced during processing is predicted and found to be in good agreement with experimental results. The parameters governing the evolution of the yield stress are shown to follow the rule of mixtures, enabling the prediction of the yield stress of any blend composition.

Influence of hybridisation and test geometry on the impact response of glass-fibre-reinforced laminated composites

This paper describes the results of falling weight impact tests (FWITs) on glass-fibre-reinforced (GRP) laminates and E-glass/Dyneema® hybrid laminates. The test programme consisted of (i) falling weight impact tests to determine the penetration energy and (ii) experiments to determine the influence of hybrid construction on damage development and impact fatigue lifetime under repeated impact conditions at sub-penetration energy levels. The objective of this work was to investigate the effect of hybridisation on the impact behaviour of GRP laminates as well as to find optimal conditions for hybridisation. It was shown that in the case of a rigid test set-up - and hence small deflections - the influence of the Dyneema® on the impact behaviour of hybrid laminates is rather small because damage processes are the result of local contact stresses in the vicinity of the impact body, whereas in the case of a compliant test set-up and large deflections the high energy storage capacity of the ductile Dyneema® fibres is used far more effectively for the protection of hybrid composite laminates. Therefore, it was concluded that in order to fully utilise the potential of high-performance polyethylene fibres it is essential that these fibres are located on the (non-impacted) tensile side of an impacted laminate and that the geometrical test conditions are such that large (bending) deformations are allowed.