Stamp forming of carbon fibre/PA12 composites – A comparison of a reactive impregnation process and a commingled yarn system

Two forms of carbon fibre reinforced polyamide 12 (PA12) were compared during non-isothermal stamp forming. The first was a stretch broken commingled yarn woven into a fabric, studied at three initial preconsolidation levels. The second was produced by in situ anionic polymerisation of lactam 12 (APLC12) in a carbon fibre textile, using a thermoplastic resin transfer moulding (TP-RTM) process. A processing window was defined for TP-RTM based upon non-isothermal polymerisation kinetics. For each material form, the effects of stamping parameters on flat plaque properties were examined. For commingled materials, the influence of preheat temperature and the initial preconsolidation level dominated, with preconsolidated materials deconsolidating strongly during the preheat cycle. For CF/APLC12 materials, the effect of material temperature and tool temperature dominated and reduced deconsolidation occurred. Hemisphere forming was enabled by stretch-broken yarn but was possible for both material classes. Over-injection moulding of recompounded CF/APLC12 composite onto stamped CF/APLC12 plate was performed, demonstrating a closed-loop recycling process.