CompositesWorld
Issue link: https://cw.epubxp.com/i/532917
JULY 2015 38 CompositesWorld INSIDE MANUFACTURING BASF high-performance materials are smart —and yes, beautiful. Our plastics and polyurethanes can be found in the innovative designs of some of the world's most popular automobiles. At BASF, we create chemistry for a better tomorrow. And a smarter ride. www.performance-materials.basf.us that lets beauty love brains. t h t l t We create chemistry anything except make the car safe." To that end, all models are equipped with crush- able composite nose cones. Even the vehicle's twin-bafe, 50-mm composite "pontoon outriggers," fared sections near the bottom of door sills, provide protection from side impacts. Because everything bolts to the chassis, rather than to the body, the latter is completely unstressed. However, when Bevan and his Trident teammates initially looked at carbon fber prepreg, he says they were disappointed with trial panels, especially for the doors. "Everything sounded awful," he explains. "Te panels were too light for us. We wanted a Grand Tourer vehicle, an expensive product, so we had to get the sound right." Because they already had a fairly light- weight chassis, the mass of body panels was less critical. "Torque is the great equalizer to lightweight construction," Bevan contends, noting that the solution was, therefore, counterintuitive: Te team hand lays glass fber composites with an unsaturated polyester matrix (Crystic 2.446 PALV from Scott Bader Co. Ltd., Wellingborough, Northamptonshire, UK), with a chopped fberglass core mat (CS mat 92, 300 and 600 g/m 2 , from Zibo PPG Sinoma Jinjing Fiber Glass Co. Ltd., Zibo, China). "We actually make our panels heavier than is strictly necessary, but when you tap on our body, it sounds like cast iron, not tin. Tat's the kind of sound we were after." Where extra strength is required, woven mat from the same supplier is used. At the front of the nose cone, for example, near the front grillwork, the layup is straight- forward 136 g/m 2 chopped strand mat construction, says Bevan. But as the layup progresses rearward toward the bonnet/ hood shut line, where the nose cone joins the chassis, techs add a combination of 50-mm woven roving strips, creating an egg-shaped crushable crumple zone, which transitions into the stainless-steel chassis frame member. Flanges and other hardware are bonded into parts during layup. Panels are cured in a paint-spray booth for 4 hours at 70°C (no vacuum is used). After demolding and degreasing, a polyester spray fller (Lesanol from Akzo Nobel N.V., Abingdon, Oxfordshire, UK) is used to smooth out surface imperfections in the dry-sanded gel coat, and then inner and outer panels are bonded together using a methacry- late adhesive (two-part, rapid-cure MMA 130 from Alsco Ltd., Swindon, Wiltshire, UK) to form a "double skin." Next, parts are primed with a two-part system and the B-surface is painted (also an AkzoNobel Lesanol grade), then panels are adhesively bonded to the chassis in 24 locations, using top-hat sections. Finally, A-surfaces are painted. Where road noise could intrude, expanded foam is used inside structures, such as around wheel wells and boot/trunk liners. Where shock absorption