The Physical Mechanisms Responsible for the Weathering of Epoxy Resins and GFR Epoxy Resins

摘要

Experiments are described where the cylindrically symmetric fields associated with the fibre/resin interface are explored by examination in the optical microscope. The patterns of birefringence show how the difference of the principal stresses vary with distance from the fibre. Changes in the load transfer at the interface during hot water uptake have been detected. Specimens examined include E and S glass fibres totally embedded in epoxy resin slabs as well as 1 mm thick transverse sections through a undirectional composite. The ultrasonic photoelastic method has given way to a more direct approach to investigate SiO2/epoxy resin interfaces, where epoxy coated X-cut slabs of quartz are stimulated piezoelectrically and the resonant mechanical vibration examined. Attempts to incorporate the quartz slabs into the transducer in visualization experiments have so far failed to produce fringes. The computer model to simulate the stress fields is described. A finite element approach is taken treating the fibre as purely elastic in an elastoplastic resin matrix. The aim is to treat the interfacial region as a third phase of finite dimensions.