Integrity of composite aircraft fuselage materials under crash fire conditions

Abstract

This paper summarises a series of small scale tests carried out to evaluate and model the postcrash fire integrity of composite aircraft fuselage structures. The US Federal Aviation Administration regulations for the penetration of an external fuel fire into an aircraft cabin after crash require a burn-through period of 4 min (FAA § 25·856 Appendix F, Part VII). Different candidate structures for the next generation of composite aircraft fuselage, provided by EADS, were investigated, including CFRP monolithic laminate and a folded core CFRP sandwich. Those materials were subjected to constant heat flux from a propane gas burner, while being held under compressive load in a small, specially designed compression test rig with antibuckling guides. The sample time to failure was measured, along with the temperatures at various points through the thickness. Modelling the thermal and structural behaviour under load required the use of a modified version of the Henderson equation, which describes heat transfer through composites under ablative fire conditions. This has been incorporated into the Com_Fire software model. Kinetic parameters for the resin decomposition reaction were determined from thermogravimetric data and other thermal parameters, conductivity and diffusivity, were measured experimentally. The paper will examine measured and modelled behaviour of the CFRP monolithic laminate.