INFLUENCE OF REPEATED IMPACT ON DAMAGE GROWTH IN FIBRE REINFORCED POLYMER COMPOSITES

The study presents the problems of the influence of repeated low velocity and low energy impacts on damage growth in carbon and glass fibre reinforced high strength polymer composite. The laminate response to impacts was analyzed, the types of damages and their interrelations were identified as well as damages mechanisms were described for tested laminates subjected to repeated impacts. The following conclusions have been drawn on the basis of completed tests: (1) composite materials with polymer matrix reinforced with continuous glass and carbon fibres demonstrate limited resistance to repeated impacts. The laminates resistance to impacts depends mainly on the properties and type of components, particularly in case of reinforcing fibres, orientation of layer under the influence of external impact; (2) tested laminates with carbon fibres are characterized by lower resistance to repeated impacts than laminates with glass fibres. This is proved by the curves of laminate response to impacts, wider damage area and tendency to laminate structure perforation as a result of repeated impacts; (3) repeated impacts lead to damage growth mainly through propagation of damage initiated in initial impacts phase. Delaminations and matrix cracks belong to the basic mechanisms of damages in composite materials; (4) composite damage propagates with increasing number of impacts in fibres orientation direction, particularly in lower composite layers. Further impacts may result in higher stress concentration and higher initiation energy causing the damage growth in various areas of the material. Further impacts increase the damage leading to gradual growth of damages initiated before.