Fiber Orientation and Mechanical Properties of Injection Molded CF/LCP Thin Plates

Fiber reinforced plastics formed a multi layer structure by injection molding. To estimate the mechanical properties of injection molded articles, sliced technique are applied. Injection molded plates with 1mm thickness under different injection speeds of Liquid Crystalline Polymer (LCP) and carbon fiber reinforced LCP composite (CF/LCP) were sliced at every 100µm layer and measured the dynamic modulus. Cox formula and laminate theory on the based on the fiber orientation and modulus of each LCP layer were applied to calculate the modulus of the CF/LCP multi layer plate. It could be confirmed that the injection molded CF/LCP plates can be treated as general laminated composite, and distribution of the modulus in the injection molded CF/LCP can be evaluated by the sliced technique. Comparing the calculated modulus to the experimental modulus in MD (machine direction) and TD (transverse direction) specimens, it is concluded that the degree of local orientation of LCP near fiber in CF/LCP is different from that of LCP without fiber. Moreover, it was cleared that the fiber orientation contributed to difference of the modulus near the surface layer due to the injection speed by evaluation of fiber orientation and modulus of sliced specimen.