Surface Quality of Carbon Fibre Reinforced Nanocomposites: Investigation and Evaluation of Processing Parameters Controlling the Fibre Print-Through Effect

Abstract

The chapter investigates the effect of the essential manufacturing parameters on the surface quality of uncoated carbon fibre reinforced composites (CFRP) used as car body panels with visible surfaces (Class A properties). A series of CFRP laminates maunfactured by the RTM technique are investigated varying in the fibre volume content (30–60%), reinforcement material (woven fabrics vs. unidirectional fibre reinforcements), curing temperatures (40–120 °C), additives (SiO2-nanoparticles as matrix fillers) and using a surface finish applied as an in-mould coating. The laminate surfaces are characterized by roughness analysis (white-light interferometry) and wave-scan measurement to quantify the influence of the different manufacturing parameters on the surface quality. Especially the used resins are intensively characterized concerning thermal properties (CTE) and total resin shrinkage. These results correlate very well with the performed analysis of surface roughness. It is found that the fibre print through effect is significantly reduced by realising low total resin shrinkage and an even distribution of resin and fibres at the surface. Thus, using of unidirectional fibre reinforcement (no weft or sewing threads; very fine filaments), low curing temperatures (slow curing processes) and an in-mould coating are most successful for reduction of fibre print through effect and getting surface similar to Class A properties. In addition, the surface quality is quite positively affected by the application of nanoparticles and also strongly controlled by roughness of tooling.