Processing and experimental micromechanics of Elium® thermoplastic composites

Developing new structural materials with high specific strength and stiffness is no longer sufficient: good environmental performance has become a prerequisite for reaching the market. In this context, the composite community has been faced with the pressing challenge of transitioning from thermosetting to recyclable thermoplastic matrices. The recent development of Elium, a range of methyl methacrylate-based resins compatible with liquid composite moulding (LCM) methods, has marked a turning point in this transition. Mitigating porosity in thick Elium laminates manufactured by LCM was the primary goal of this work, given the suspected tendency of the monomer formula to boil during the in-situ polymerisation step. Thermochemical modelling was used for assessing the influence of various parameters on the evolution of preform temperature during polymerisation, thus preventing the occurrence of thermal porosity. In parallel, a miniature infusion setup was designed for monitoring void growth in 2 cm-thick Elium laminates via dynamic X-ray computed tomography, which helped identify and decouple various mechanisms responsible for void formation in a proof-of-concept study. The second part of the work explored the deformation and failure mechanisms occurring at the constituent level in Elium composites. Using nanoscale digital image correlation, the strain fields in between two adjacent fibres of a composite specimen subjected to transverse compression could be successfully captured. Small-scale indentation techniques were also used to quantify the influence of fibre proximity and physical ageing on the elastic properties of the Elium polymer, and assess the thickness and mechanical response of the fibre-matrix interphase region.(FSA - Sciences de l'ingénieur) -- UCL, 202