Experimental and numerical investigation of composite energy absorbers using variable load concept

Abstract

Composite materials have been extensively used in modern helicopters’ structures to reduce structural weight. These include energy absorption components to improve crashworthiness performance. Despite composite material can offer higher Specific Energy Absorption (SEA) than traditional metallic materials, there are limitations from the current energy absorbers in a practical helicopter crash scenario, such as under-utilisation of the crushing stroke leading to inefficient material usage and occupants experiencing unnecessarily high deceleration. This paper describes the results of a project to develop the improved system for the crashworthiness. As part of this project, a novel Variable Load Concept (VLC) to improve the performance of the energy absorption has been introduced [1] in which, the crushing force can be controlled through the radius size of trigger mechanism and the use of pressurised composite tubes. As the composite specimens of increasing crush speeds were tested, the concept and the system were developed and further validated. The crush speeds included quasi-static, 2 m/s and 8 m/s load conditions. The validation of the VLC through design and test of the energy absorbing pressurised composite tube system is described in details. The final results showed that the VLC with pressurised composite tube system can be used in crashworthiness applications, and that the improvement in energy absorption has been enabled significantly. Finally, an explicit finite element study was carried out by using finite element (FE) software VPS (formerly known as PAM-CRASH) and the results showed very good agreement between FEA model and experimental work.