Inverse solution methods for in-situ characterisation of damage in composite structures

Delamination damage is one of the most important damage modes in composite laminates, which could significantly reduce the stiffness and strength of the structure. Therefore, there is great interest in developing reliable damage identification and characterisation methods to evaluate the residual strength and provide a prognosis for the remaining life of the structure. This thesis presents a novel two-step approach for detecting, locating and quantifying delamination damage in composite structures. In the first step, baseline-free methods such as the gapped smoothing method and the continuous wavelet transform method are applied to locate the edges of the damage from vibrational curvature data. <br><br>In the next step, the severity of delaminations in the through-thickness direction is determined using newly developed analytical and computational inverse methods. The equivalent condition between the soft inclusion model and the delamination model has been firstly demonstrated and manifested both analytically and numerically. This two-step approach quantifies the stiffness reduction in the damage region, which is essential for managing structural safety. Practical aspects of the implementation of this procedure are discussed, and numerical and experimental validations using a scanning laser vibrometer are presented. Various damage patterns have been considered. Finally, the proposed two-step approach is extended from beam-like structures to plate-like structures.