Post-impact recovery in 3D-printed thermoplastic continuous fibre composites via fusion bonding

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The post-impact recovery behaviour of 3D-printed continuous fibre-reinforced thermoplastic composites (CFRC) repaired via fusion bonding was investigated. Unidirectional and cross-ply laminates were manufactured using a Markforged® fused filament fabrication (FFF) system and subjected to low-velocity impact loading, followed by thermal post-processing through hot pressing. Internal damage evolution and defect closure were characterised using X-ray computed tomography (CT) and scanning electron microscopy (SEM), while compression-after-impact (CAI) testing was used to quantify residual and recovered mechanical performance.The results demonstrate a strong dependence of impact damage development and post-impact recovery efficiency on laminate architecture. Distinct damage modes across the different stacking sequences led to markedly different recovery responses following fusion bonding, with effective reduction of interlaminar delamination and internal void content for matrix-dominated damage states. Rather than proposing a novel repair technique, this study establishes a damage-mode- and stacking-sequence-dependent benchmark for fusion-bonding-based recovery in impact-damaged 3D-printed thermoplastic CFRC, providing a reference framework for interpreting recovery limits and evaluating more advanced or in-situ healing strategies.