Abstract: The effects of molding temperature， molding pressure， pressure holding time and clamping speed on the surface quality of carbon fiber/epoxy sheet molding compound molded products were investigated by means of an orthogonal test. The variance analysis indicated that the influencing factors on the surface roughness became more significant by the following order： molding temperature T > pressure holding time t > molding pressure P > clamping speed v. Through the multiple comparison of the Duncan’s test， the difference in average values between the different levels of various influencing factors was further discussed， and the relationship diagram of the measured average values of surface roughness corresponding to each factor was constructed. The molded products showed a slow increase in surface roughness at first， followed by a sharp increase with increasing the molding temperature. The effects of pressure holding time and molding pressure on the surface roughness were opposite. The surface roughness did not change significantly with an increase in clamping speed. The optimal process parameters were obtained as follows： molding temperature T=130 ℃， molding pressure P=600 kN， pressure holding time t=720 s， and clamping speed v=15 mm/s. The molding experiment indicated that under these optimal process parameters， the surface roughness was reduced by 19.3 % compared to the minimum value obtained from the orthogonal test. This result suggests that the surface quality of molded products was improved effectively.

Key words: sheet molding compound, orthogonal test, analysis of variance, process parameter optimization, surface roughness