Colloquia

Samenvatting

Unidirectional carbon-fiber reinforced thermoplastic polymers (UD CFRTPs) are gaining increasing attention due to their recyclability and potential for automated manufacturing. However, manufacturing-induced defects remain a major challenge as they can significantly affect mechanical performance and introduce large uncertainties in structural design. This work presents a multiscale modelling framework to investigate the mechanical impact of common manufacturing-induced defects in UD CFRTP laminates. The framework employs a two-step homogenisation and stress-strain field recovery method to efficiently incorporate defects into finite element analyses. 
Experimental observations of a reverse-formed laminate representative of stamp-formed products with surface-ply fibre waviness revealed variations in fibre orientation, ply thickness, and fibre volume fraction throughout the surface ply and several underlying plies. These defects were quantified and evaluated directly with the modelling framework. Results showed that surface-ply fibre waviness is the dominant contributor to strain concentrations in the laminate. Including ply thickness variations led to an additional increase of up to 20% in surface-ply shear strain, while variations in fibre volume fraction showed a negligible effect. 
Overall, the framework proved effective in incorporating manufacturing-induced defects into UD CFRTP analyses. The implementation of the ply homogenisation and stress-strain field recovery highlighted the importance of boundary conditions for accurately preserving the ply-level stress-strain fields. This work demonstrates how experimentally observed manufacturing defects can be integrated into a multiscale modelling approach to efficiently identify the defects most critical to mechanical performance, providing insight for improved design and manufacturing strategies.