A study on damage evolution in composite laminates. A Ritz computational framework for VAT plates and experimental tests for SHM systems

This thesis investigates the development and implementation of numerical damage models and experimental tests for damage detection and monitoring in thermoplastic composite plates.The core of this thesis is a numerical formulation based on the Ritz method within the Continuum Damage Mechanics framework, offering insights into the initiation, evolution, and failure of composite laminates, including Variable Angle Tow configurations. This method shows a remarkable reduction in computational costs compared to traditional approaches. However, the study also identifies limitations in the single-domain Ritz approach, highlighting the need for adaptive techniques to mitigate spurious numerical effects.Additionally, part of the research activities have been performed at Centro Italiano Ricerche Aerospaziali, collaborating on an ongoing project featuring experimental tests on thermoplastic composite materials. This experimental campaign involved testing thermoplastic composite coupons equipped with various sensors, such as Fibre Bragg Gratings and distributed fibre optics. These tests aimed to evaluate the ability of the considered sensors to detect and localise damage under controlled conditions. The findings indicate that both sensor types are effective in damage detection, providing essential data for refining the numerical models, and laying the groundwork for the development of a fully functional SHM system for thermoplastic composite materials in aerospace applications.Future research directions include extensive experimental validation of the numerical models, integration of advanced sensor technologies with SHM systems, and the development of sophisticated algorithms for data analysis and damage prediction. The ultimate goal is to create more robust and reliable SHM systems, ensuring the safety and longevity of engineering structures.