Experimental investigation of thickness effects in the manufacture of thick-section composite structures using liquid thermoplastic resin

Thick-section composites (10–100 mm) are increasingly used in structurally demanding applications. Growing interest in sustainable alternatives has driven the development of recyclable, room-temperature-processable liquid thermoplastic resins to replace thermosets in vacuum-infused composites. However, managing the thermal effects of polymerisation to avoid boiling and defects remains a challenge in thick-laminate manufacturing . While low-exotherm grades are available, their behaviour in thick laminates remains poorly understood. This study examines the exothermic polymerisation of Elium® 188 XO, a low-exotherm thermoplastic resin, in laminates with thicknesses of 9.5 mm, 17.9 mm and 26.4 mm. Process times are presented to support implementation. Using five embedded thermocouples, maximum temperatures of 86.5°C, 92.6°C and 93.9°C were recorded, all remaining below the resin’s boiling point. The results indicate a progressive increase in interlaminar temperature with increasing laminate thickness. Ambient-temperature-adjusted data showed peak increases of 2.7°C and 3.1°C between successive laminate thicknesses. These findings provide critical insights into polymerisation behaviour, informing process optimisation and industrial adoption.