Abstract
The mechanical properties of carbon-fibre composites (CFC) when exposed to constant environmental conditions are well known, but the effects of rapid high temperature excursions (thermal spikes) are less well understood. The effects of such thermal spikes on laminates of CFC subjected to a range of conditions of temperature, humidity and spiking have been investigated. These conditions were intended to represent those that could be met in service by a specific component andformed part of the airworthiness clearance procedure. Details of the experimental programme are reported together with the results of mechanical tests and optical examination. Comparisons are made with laminates which had received no environmental exposure. Both uniform moisture distributions and moisture gradients were investigated.
Thermal spiking of laminates containing more than 1·3% moisture was found to increase both the rate of moisture uptake and the equilibrium moisture content. This was considered to be associated with matrix damage but only under the most severe conditions could this be confirmed by optical examination.
The combined effect of the various combinations of moisture content, thermal spiking and testing temperature on the mechanical properties is quite complex and the tests reported here were not sufficiently exhaustive to establish the contribution made by each effect. The consequence of thermal spiking is a modified total moisture content and distribution, from one that is uniform to one that has a higher concentration at the surface and is of a higher average content. Thus moisture alone could be responsible for the extra loss in strength, or it could be due to the spike induced damage. Sufficient evidence is available, however, to suggest that, at least for the range of temperatures investigated, the effect of thermal spiking damage is small compared to other environmental effects.
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Collings, T.A., Mead, D.L., Stone, D.E.W. (1987). The Effects of High Temperature Excursions on Environmentally Exposed CFC. In: Marshall, I.H. (eds) Composite Structures 4. Springer, Dordrecht. https://doi.org/10.1007/978-94-009-3457-3_27
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DOI: https://doi.org/10.1007/978-94-009-3457-3_27
Publisher Name: Springer, Dordrecht
Print ISBN: 978-94-010-8048-4
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