Economical carbon and cellulosic sheet moulding compounds for semi- and non-structural applications

Abstract

The use of discontinuous carbon fibre plastics (DCFP) in automotive applications is increasing. The material offers a light weight and stiff alternative to conventional short-fibre glass-reinforced composites such as sheet moulding compounds (SMC). Prohibiting factors to wider utilisation of this material are cost and formability. Carbon moulding compounds available commercially are expensive containing high fibre volume fractions (Vf) which hinders or stops flow during moulding. This study examines the flexural and impact performance of cheaper carbon fibre (CFSMC) and cellulosic SMC grades produced using a standard, polyester, SMC production route where flow during moulding has be retained. Mechanical properties were assessed relative to increasing fibre length, volume fraction and bundle morphology. It was found that although much lower Vfs were employed, the new CFSMC grades offered superior impact strength when compared to commercially available DCFPs. The optimal impact performance achieved by CFSMC and cellulosic SMC samples were 103 KJ/m2 and 76 KJ/m2, respectively. These CFSMC and cellulosic SMCs had an average density of 1.62 g/cm3 and 1.57 g/cm3 compared to an average commercial value of 1.50 g/cm3, respectively. The developed SMCs have the potential as a cost-effective replacement to commercial carbon fibre SMC grades in semi- and non-structural applications where impact rather than stiffness is paramount.