A step toward digital twin accuracy in composite manufacturing: Pioneering contour method in polymer composites

Digital twinning is revolutionizing composite manufacturing by optimizing product design and enhancing structural integrity through total stress assessment. However, accurately validating residual stress in numerical simulations remains a significant challenge. The present research pioneers the application of the contour method to non-conductive polymer composite materials using diamond wire cutting, breaking away from its traditional use on conductive materials. It establishes a robust experimental framework for assessing and refining numerical simulations in digital twinning of composite structures. A simple epoxy-carbon fiber reinforced cross-ply laminate with unbalanced asymmetric layup is employed in this study. It is ensured the material is elastically deformed during cutting by comparing the operating temperature and the glass transition temperature determined using Differential Scanning Calorimetry. The cut surfaces are thoroughly assessed using optical, confocal, scanning electron microscopy and high-resolution surface topological scanning to validate the contour method assumptions. This includes characterization of the microstructure, material defects and cutting artefacts affecting the deformation topology of the cut surfaces. The paper sets a minimum resolvable length scale for residual stress, considering the size of constituents and surface roughness caused by diamond wire cutting. Finally, through thickness Residual stresses of cross ply laminate measured by the Contour Method is presented and validated against Pulse-method based slitting analysis.