Fumiaki Baba

Structure and mechanical properties of injection moulded CF/LCP thin plates

The effect of injection speed on the structure and bending properties of carbon fibre (CF) reinforced liquid crystal polymer (LCP) injection moulded plates were investigated. The distribution of the modulus in injection moulded LCP and CF/LCP thin plates made using two different injection speeds was investigated by taking slices at 0.1 mm intervals. Moreover the modulus of the CF/LCP thin plate was estimated by the Cox formula and by laminate theory from values of the fibre orientation and modulus of each LCP layer. It was found that the differences in the bending properties and structures due to changes in injection speed were not remarkable. The differences in the fracture behaviours with changes in the cutting position were caused by the differences in the modulus of each layer as in the laminated composite. It was confirmed that injection moulded CF/LCP can be treated in general as a laminated composite, and that the distribution of the modulus in injection moulded CF/LCP could be evaluated by the slicing technique. Comparing the calculated modulus with the experimental one in the machine direction and the transverse direction revealed that the degree of local orientation of the LCP domains near the fibres was different from that of LCP without any fibre. Moreover, it was shown by evaluating the fibre orientation and modulus of the sliced specimens that fibre orientation contributed to the difference in the modulus near the surface when the injection speed changed. It was also verified that the prediction method suggested in this paper is valid to estimate the modulus of thin injection moulded CF/LCP plates.