Study of an energy absorption element for leading edge slat or fixed leading edge through numerical simulations

Abstract

The present final work project has been performed at Sonaca, a Belgian company which is producing aeronautical components. The objective was to study composite leading edge slat designs and more precisely the feasibility of using aluminium honeycomb cores as energy absorption elements to handle the issues of composites parts submitted to bird impact. After a validation of the numerical simulation on a well known aluminium slat design, two composite designs have been studied. A hybrid design which combines an aluminium slat top skin and a composite rear structure has been found compliant with birdstrike requirements while cutting down the weight of the whole structure by 17.2% and the weight of the slat itself by 27.1% with respect to a reference aluminium slat design. Thereafter, the constitutive model used to represent the crushing behavior of aluminium honeycomb core has been identified using quasi-static crushing experiments before it has been validated under dynamic conditions using an birdstrike experiment carried out on a fixed leading edge. A full composite slat design associated to a fixed leading edge reinforced with aluminium honeycomb core has been proven compliant with birdstrike requirements while cutting down the weight of the whole structure by 17.5% and the weight of the slat itself by 41.7% with respect to a reference aluminium slat design. Key prerequisites for slat design integrating aluminium honeycomb cores such as the absence of localised stiff points and a sufficient stiffness of the part which support the core have been identified. The influence of the some design parameters has finally been assessed to give a first insight of the elements which should be taken into account during sizing of fixed leading edge reinforced with aluminium honeycomb cores.