Fatigue damage in GFRP

Purpose - Composite materials are increasingly used in the structural and mechanical fields, thanks to their high strength-to-weight ratios and the possibility of tailoring them to meet specific requirements. This study is focused on the damage to a glass fiber reinforced composite under different loading conditions. The aim is to find, by coupling mechanical tests with thermal analyses, a damage parameter, able to define the damage initiation in the studied material. Design/methodology/approach - The object of this work is a glass-fiber reinforced plastic ('GFRP) laminate. To study the damage of this material under different loading conditions, static, dynamic and fatigue tests were carried out. During these tests, the surface temperature of the specimens was monitored by means of an IR-camera. In the dynamic tests, a D-mode ('dissipation mode) analysis was also performed allowing the dissipated energy to be determined. Findings - In the literature, thermography is an experimental technique which has always been applied to the study of homogeneous materials. Results obtained from the proposed experimental tests on this GFRP composite show how this practice can be applied also to this kinds of materials, to identify their damage initiation. From these observations, the results can be used to definite a stress corresponding to the damage initiation, which can be related to the fatigue behavior, and useful in design stage with these materials. Originality/value - This paper provides for a useful tool to understand and predict fatigue behavior of a GFRP composite, from thermographic observations. Applications of thermography to the study of composite materials is an innovative research field, and the presented results seems satisfactory and promising for further experimental investigations.