Simulation based on computational solid mechanics models describe the response of structures, as a function of their geometry, loading, boundary conditions, material properties and manufacturing process. Digital Twin Validation i.e. 'the process of determining the degree to which a model is an accurate representation of the real world, from the perspective of the intended uses of the model', is of the most important aspects of engineering simulation. It is the responsibility of the digital twin users to perform sufficient validation of the models developed, by reference to experiments specifically designed for this purpose. Optical measurement and other relevant experimental methods have reached a sufficient technology readiness level that enable displacement or strain data over large areas or even the entire structure to be reliably captured during an experimental test and thereafter visualized and analyzed. Such developments have provided the background for a more comprehensive approach to model validation used in engineering design and evaluation of structural integrity, which could lead to optimized and less conservative designs. An important parameter in digital twins is the mechanical performance of the materials and how it is affected by the manufacturing process, especially when recycled materials are used. During the session, important recent advances on simulation model development, validation methodologies and the performance of recycled composites will be presented by researchers from industry and academia, focusing on validation of novel aircraft structural components and structural details.