Simulation-guided process development for thermoforming of aligned discontinuous fibre composites

Aligned discontinuous fibre-reinforced composites (ADFRCs) combines near-continuous fibre mechanical properties with the formability and recyclability needed for sustainable manufacturing of composites. Structural properties have been demonstrated at coupon scale, and recent studies have shown that ADFRCs can be formed into complex geometries. However, these forming trials remain largely empirical. The interplay between matrix viscoelasticity, fibre overlap evolution, and the requirement to form below the melting temperature to preserve fibre alignment creates a narrow process window that is difficult to navigate through trial-and-error alone. This study presents a forming simulation framework to contribute process development. ADFRCs comprising 3 mm carbon fibres in a bio-based poly(L-lactic acid) matrix were manufactured via the HiPerDiF process. Viscoelastic constitutive models implemented within Abaqus/Explicit predict fibre sliding, overlap evolution, and forming feasibility, where the tensile constitutive model is experimentally validated; shear and bending models are supported by sensitivity analysis demonstrating their secondary role under the conditions studied. Parametric development identified that a forming temperature of 140 °C, a rate of 375 mm min -1 , and corner-constrained boundaries yield defect-free laminates. This was confirmed experimentally in a single forming trial without iterative optimisation. The framework demonstrates that simulation-guided process development can reduce dependence on empirical trial-and-error by narrowing the process window before physical trials.