Characterisation and modelling of structural integrity of carbon fibre wing box laminate subject to fire

Delamination damage occurs in carbon fibre reinforced plastic (CFRP) as a result of fire exposure, followed by extensive resin decomposition and charring. The initial delaminations are detectable using portable ultrasonic equipment and appear to coincide with the onset of resin decomposition, as measured by thermogravimetric analysis (TGA). However, further work is needed to determine the exact temperature for permanent damage. The spread of delaminations through the structure correlates with a reduction in compressive strength which can be described using the ‘two-layer' model. Temperature-dependent thermal properties, including anisotropic values of thermal conductivity, enabled the 3-D temperature field to be modelled using a finite element (FE) package. The high in-plane thermal conductivity of CFRP can result in indirect thermal damage in regions adjacent to the zone of fire exposure.