X-ray phase contrast microtomography for the analysis of the fibrous microstructure of SMC composites

X-ray microtomographs of samples cut from non-deformed and compression moulded Sheet Moulding Compounds (SMC) plates have been analysed using the phase contrast mode. Results emphasise a significant decrease of the porosity after moulding, this phenomenon being enhanced with increasing the initial SMC temperature. They also show that pronounced migration of the polymer–matrix occurs through the thickness of the plates during compression moulding. The substructures of compression moulded plates through their thickness exhibit a core zone sandwiched between upper and lower skins. Inside the skins, the fibre content and the porosity are weaker than in core zones, and fibre-bundles are highly broken up. On the contrary, fibre-bundles remain preserved in core zones. Therein, the significant flattening and widening of bundles, their weak bending as well as their orientation have been quantified.