Effect of Injection Speed on Internal Structure and Mechanical Properties in Short Glass Fibre Reinforced Polyamide Injection Mouldings

Injection mouldings of glass/polyamide can have heterogeneous features such as skin/core structures, depending on the injection moulding conditions. The structure of glass fibre reinforced polyamide injection mouldings is discussed on the basis of the results of acoustic emission and fractographic observations associated with static and fatigue testing. The heterogeneous structures identified by variations in fibre distribution were affected by injection moulding speed. The mechanical properties and the fatigue life were also affected by the injection speed because there is a strong relationship between the internal structure and the fracture behaviour. In particular, the existence of resin rich regions dominates the fracture behaviour in both tensile and fatigue testing.