Fatigue behaviour of composite sandwich beams strengthened with GFRP stiffeners

Abstract

This paper investigated the fatigue behaviour of composite sandwich beams, which consisted of glass fibre reinforced plastic (GFRP) skins and a foam core, strengthened with transverse or longitudinal GFRP stiffeners. A total of 42 specimens were prepared using vacuum-assisted resin transfer molding technology. The effects of GFRP stiffeners (transverse or longitudinal) on failure mode, bending deflection behaviour and fatigue life of specimens were investigated. Experimental results revealed that for beams with transverse stiffeners, the failure initiated from core shear and interface debonding between stiffeners and foam core; while for beams with longitudinal stiffeners, the failure was due to GFRP skins compression failure or longitudinal GFRP stiffeners buckling or fracture failure. Moreover, the bending strengths and failure fatigue cycle numbers of beams with longitudinal GFRP stiffeners were all larger than those of common beams or beams with transverse GFRP stiffeners. Lastly, a fatigue damage model was developed to predict the failure cycle number under different loading levels. The validity of the proposed model has been verified to estimate the fatigue behaviour of sandwich beams strengthened with GFRP stiffeners.