THE APPLICATION OF SCANNING LASER EXTENSOMETRY TO EXPLORE THERMAL CYCLING CREEP OF METAL MATRIX COMPOSITES

In-cycle creep data for metal matrix composites undergoing thermal cycling while under load are essential to the understanding of composite stress relaxation mechanisms. Such information may enable life predictions to be made for structural components in thermal cycling environments. Non-contacting laser scanning extensometry is here shown to be a relatively straightforward technique for making incycle strain measurements. Accuracy of +/- 2-mu-m is maintained. Preliminary results utilizing this novel technique are shown for the Al-10vol.%C fibre composite system. The composite is observed to creep in the reverse sense to the applied load during the cooling part of the cycle. This is unsurprising in view of calculations from the Eshelby model, indicating that internal stresses from differential thermal expansion can be highly significant compared with those from an external load.