Experimental evaluation of residual tensile strength of hybrid composite aerospace materials after low velocity impact

Although much work has considered hybridised Carbon and Glass Fibre Reinforced Polymers to positively influence the performance of composite structures when subjected to transverse impact loading, there is limited understanding considering low energy impact levels (<= 10J) - in particular how variation in impact energy influences damage formation and post impact tensile strength. Herein, low velocity impact and residual tensile strength after impact tests are completed on four laminate designs (one pure Carbon laminate layup and three hybrid Carbon and Glass layups). Three repeat tests and three graduated low energy level impacts (<= 10 J) are considered along with pristine laminate performance. The impact response was evaluated in terms of surface damage size by visual inspection, and the evolution of peak force and stiffness with impact energy level. The contribution of this paper is the first presentation of a detailed experimental study on the tensile performance of hybrid composite materials subjected to a graduated range of low energy level impacts. The methodical experimental work demonstrates how the hybrid layup influences the scale and form of damage. By distributing the glass plies through the laminate, as opposed to clustering the glass plies at the inner or outer mould surfaces, more favourable residual tensile strength and strain to failure is demonstrated.