Residual Stress Measurement on Fibre-metal-laminates

Abstract

A comparison between different residual stress measurement methods on fibre reinforced metal laminates was made. The methods used were X-ray diffraction, neutron diffraction and strain measurement throughout destructively produced stress release. Good agreement was found between the different methods. For these types of laminates, thermally caused residual stresses arise during manufacture. Stretch operation of the laminate will modify the residual stress state. It is well documented that the residual stress state greatly affects the fatigue properties of these laminates, not only during the fatigue initiation stage but also during fatigue crack propagation [1–3]. Neutron diffraction residual stress measurements have also been performed on fatigue-damaged material, specifically in the wake of a fatigue-induced metal crack in the laminate. Delamination and fibre degeneration occur to some extent in the surroundings of the fatigue-induced metal flaw. This will cause a relaxation of the compressive residual stress, and it will affect further development of the fatigue damage.