CompositesWorld
Issue link: https://cw.epubxp.com/i/576646
OCTOBER 2015 72 CompositesWorld WORK IN PROGRESS » Automakers and their suppliers have been painting glass fber-reinforced composite exterior body panels, including those made from sheet molding compound (SMC), for many years. SMC painting, in particular, came in for its share of problems (see "Learn More," p. 76) but today, can be integrated into OEM production and assembly processes. But painting and decorating carbon fber composites has a shorter history, and almost none in connection with volume produc- tion. Carbon body panels are typically limited to very low-volume sports cars, and here, OEMs are often content to play up the natural look of carbon fber weave by applying a clearcoat. By 2025, however, when new US corporate average fuel economy (CAFÉ) requirements and European CO 2 emissions limits kick in, carbon fber could be in the auto industry mainstream as engineers seek to tap the material's high strength- and stifness-to-weight ratios as a partial solution to the conundrum of nearly doubling the average number of miles a vehicle can travel on a given volume of fuel. With respect to weight reduction, As tougher emissions standards loom, one supplier's study sheds light on the challenges of applying flaw-free primer and paint to production CFRP exterior body panels. Carbon fiber auto body panels: Class A paint? FIG. 1 Textured grooves that kept appearing on the painted panels at room temperature prompted researchers at BASF to measure the topography of the unpainted carbon fber substrate with an optical proflometer. Scans of cross sections of the unfn- ished panels at room temperature revealed grooves on the surface approximately 5 microns deep. The grooves aligned with the weave of the fber mat. As the carbon fber substrate was heated to 100°C, the grooves became less pronounced, shrinking to about 2.5 microns. The periodicity of the grooves aligned with the grooves of the painted panels, meaning the texture could be explained by diferential expansion/contrac- tion in the substrate. Source | BASF By Michael LeGault / Contributing Writer 4 3 2 1 0 -1 -2 -3 -4 position (mm) displacement (microns) displacement (microns) position (mm) 2 1.5 1 0.5 0 -0.5 -1 -1.5 -2 -2.5 25 ° C 100 ° C 02 46 81 0 0 46 81 0 Overlay of 25 ° C and 100 ° C (uncoated) Diference between 25 ° C and 100 ° C (uncoated)