Cyclic Behaviour of Unidirectional Hybrid Interlayer Glass/Carbon and Carbon/Carbon Composites

The lack of ductility is a major drawback of fibre reinforced polymer (FRP) materials. As it is known, these materials are stiff and strong, but brittle with little or no warning before final failure. In the last decades, some solutions have been proposed with the aim of having FRP materials with pseudo-ductile behaviour. For instance, the use of unidirectional (UD) hybrid FRP materials (i.e. composites in which two different reinforcing materials are combined in the same polymeric matrix) can lead to tensile pseudo-ductile failure development. This is characterized by fragmentation of the low strain (LS) material and dispersed delamination of the LS material fragments from the undamaged high strain material. This concept is relatively new in the composites field, and almost unexplored in civil engineering applications. Nowadays, despite the research carried out in this area, the cyclic behaviour of pseudo-ductile UD hybrid composites is a remaining open question. The main goal of the present work is to give new insights on the tensile-tensile cyclic behaviour of two pseudo-ductile UD hybrid composite systems, one comprising glass and high modulus carbon fibres and the other comprising standard-modulus carbon and high modulus carbon fibres. The behaviour under quasi-static and cyclic loading is investigated and the results are compared. Digital image correlation is used to observe damage evolution. The experimental program is described and the main results are presented and analysed.