RELATED EXPERIMENTAL AND MODELLING METHODS OF ANALYSING CRACK INITIATION AND PROPAGATION CONDITIONS IN POLYMER MATERIALS

摘要

A test method has been devised that initiates and propagates a crack in polymer materials that avoids the need of an impact device. This is to take advantage of the good thermal insulation properties of polymers and similar materials and their tendency to be embrittled when cooled to low temperatures. Crack initiation in an embrittled part of the specimen is a simple process and it can be arranged for the crack to then propagate into the main part of the specimen which can have a variety of different shapes and include bonded joints and other features. Also, the stress loading for the main part of the specimen can be varied to relate to the different conditions in which a material may be employed. With impact testers, that also apply dynamically a three-point bend or other test condition then a problem can be in determining how much the crack initiation and propagation is due to the impact transient forces relative to the three-point bending or other loading of the specimen. Although impact testing is a very useful and realistic test, it can be difficult to determine precisely the threshold of crack initiation and propagation and other key factors that the proposed test method achieves. In many ways, impact testing and the proposed method complement each other.