Measurement of assembly stress in composite structures using the deep-hole drilling technique

The deep-hole drilling (DHD) method is a residual stress measurement method that is widely used for measurements in thick metallic components. In the DHD method a reference hole is first drilled through the thickness of the component. The diameter of the hole is measured accurately and then a cylindrical core of material around the hole is trepanned from the component, relaxing the residual stresses in the core. Finally, the diameter of the reference hole is re-measured and the change in diameter used to calculate the residual stress. In this work the method is used to attempt the measurement of cure and assembly stress in thick AS4/8552 composite laminates. The results indicate that although the DHD method cannot measure cure stress, it is able to measure assembly stress. Futhermore, a modification to the standard DHD method allows the through-thickness component of assembly stress to be measured in angle components.