CompositesWorld
Issue link: https://cw.epubxp.com/i/576646
OCTOBER 2015 74 CompositesWorld WORK IN PROGRESS Follow-up trials with panels subjected to multiple coats of primer and multiple sanding (a technique currently used to reduce texture on the Corvette hood and glass-flled wind blades, for example) did not eliminate the texture once the panels cooled to room temperature. Te fnished panels, both sanded and unsanded, were then reheated to the bake temperature of 100°C. Immediately after removal from the oven, the unsanded panels were, again, texture-free; however, the sanded panels had reverse structure — that is, the grooves were now ridges. Once again, as the panels cooled, the groove-like texture reappeared. "At this point, we were scratching our heads," Campbell admits. "We suspected what we were seeing could somehow be explained by diferential cooling between the substrate, primer and clearcoat." To better understand the results, the team obtained an optical proflometer, an instrument used to measure the roughness/ smoothness of 3D surface topography. Optical images taken of the composite panel surface showed large carbon fber bundles, 1.5-2 mm wide, embedded in resin-rich domains of epoxy as much as 0.25 mm wide and 0.25 mm deep. Scans of cross sections of the unfnished panels at room temperature also revealed grooves on the surface approximately 5 microns deep. Te grooves aligned with the weave of the fabric. As the unfnished carbon fber substrate was heated to 100°C, the grooves became less pronounced, shrinking to about 2.5 microns (Fig. 1, p. 72). WHETHER YOU'RE BUYING 2 OR 200... ...THERE'S A SUPERIOR TOOL IN YOUR FUTURE! Tools for Composite, Aluminum, Titanium, Steel. Quick Turnaround on Tools & Coating. ORDER RAPID CUSTOM MADE: 800.428.TOOL (8665) TO BUY ONLINE STOCK: SUPERIORTOOLSERVICE.COM