Ultraviolet Digital Image Correlation for Molten Thermoplastic Composites under Finite Strain

The thermostamping process used to fabricate thermoplastic prepreg composites is widely studied due to its use in several applications in the automotive and aerospace industries. In recent years, different constitutive mechanical models and new numerical techniques have been proposed to simulate this process. However, from an experimental point of view, no substantial progress has been recorded on the experimental methods used for the characterisation of thermostamped thermoplastic prepreg composites. Moreover, there is currently no experimental protocol to visualize or analyse deformation fields at temperatures above the melting point of a material during the characterisation process. The knowledge of these fields allows precision modelling of the mechanical behaviour of this type of material. Therefore, the aim of this paper is to propose a new experimental protocol that uses a digital image correlation method, which faces constraints such as light reflections on either the yarns or the molten thermoplastic matrix. The proposed solution uses an ultraviolet light source and a photoluminescent powder to make the speckle pattern. This approach avoids any visible reflections, since the sample itself is the visible light source.