Multi-axial fatigue life estimation of unidirectional GFRP composite

Aim of this work is to test and understand the mechanical behaviour, in multi-axial stress conditions, of a composite material (E-glass reinforce fibres and vinyl-ester matrix) used to build a structural component: a corner beam of bus cabin. A series of experimental tests is performed on specimens cut out from this beam. Different unidirectional (UD) fibres orientations with respect to the direction of load application are considered: longitudinal (0°), normal (90°), inclined at 30° and 45°. Static and fatigue characterization are carried out to identify the mechanical behaviour in terms of σ–N curves. Obtained fatigue data are then interpolated by fitting the parameters required for multi-axial models of fatigue life estimation. A final comparison with the literature data is included, proposing a simple tool to evaluate the damage evolution of E-glass reinforced composites during fatigue life.