Lubricated compression of BMC, a concentrated and fibre-reinforced granular polymer suspension

Bulk moulding compounds (BMCs) are thermoset polymer composites widely used in electric and automotive industries. During their processing by injection, BMCs look like fibre-reinforced granular suspensions in the form of pastes, the rheology of which is not well known. For that purpose, lubricated compression tests were performed on BMC samples with various formulations. Firstly, results show that samples flow without sticking to the rheometer’s plates, validating the efficiency of the lubricant. A correction, which requires few assumptions on the rheology of BMC, is then proposed to account for its contribution to the overall axial stress. Thereby, the influences of the axial strain rate, the loading path, the polydispersity of the mineral filler and the fibre content on the BMC flow are analysed. A 1D elementary non-linear viscoelastic model is proposed to capture the main observed trends.