Influence of delamination on fatigue properties of a fibreglass composite

Residual fatigue life, stiffness and strength are directly related to presence of defects and damages in composite materials, among which delamination is one of the most diffused. This work aims to study the effect of delamination on fatigue behaviour of a glass fibre reinforced composite. Experimental tests are carried out to check fatigue life decrease of delaminated specimens, with a Teflon layer at half of its thickness, by a comparison with undamaged material. In order to evaluate defects presence and their progressive evolution, infrared thermography is taken into account, monitoring surface temperature of the damaged and undamaged samples. Static and fatigue tests are carried out, and a high cycle fatigue limit is identified for this composite material. Three approaches, based on thermal observations of static and dynamic tests at increased stress amplitude, revealed a relation between thermal response of the material and the fatigue limit. From this standpoint, thermography can be indicated as a valid tool to monitor damage initiation and its evolution during testing, and to estimate fatigue life.