SEP 2018


Issue link:

Contents of this Issue


Page 41 of 91

SEPTEMBER 2018 40 CompositesWorld FEATURE / Safe Cycling composite material design is only as good as its manufacturability. Bressan identifies four equally important goals for every commercial design. First is cost. Bressan, whose background includes Formula One and America's Cup composite racecar and yacht designs, emphasizes that the first design goal is to consider the cost not only of the material itself, but "everything you design, the complexity you bring." e second priority is weight, which Bressan points out depends on the fiber direction, or fiber architecture. "Every single tube on a bicycle works differently — some working more in torsion, others more in bending and still others working more in compression, for example," he explains. Fiber architecture can be optimized for these loads. "is is the beauty of using composite materials compared to aluminum or titanium or metals in general, because the material itself is variable." ird is stiffness. "Stiffness is so impor- tant because it is a matter of energy," Bressan says. "You react fast when you need to react, you push the bicycle and all the energy that you put into the bike becomes your speed. So the stiffness becomes a priority." A bicycle with inad- equate stiffness — for example, one made using low-modulus carbon fibers — can deform as the rider pumps on the pedals and pulls up on the handlebars to climb a hill or increase speed. When the bicycle deforms, some of the rider's energy is lost. Bressan explains, "e material absorbs that energy and instead of having energy that pushes you, and you go faster, you lose part of that energy." e fourth and final consideration is safety. Optimization of material and manufacturing choices to best support specified critical load and performance targets is also the road to safer operation, Bressan says. And what defines optimum for a particular bike model depends to a significant degree on our first design factor, its intended purpose or use: A mountain bike cannot be designed peril- ously close to the breaking point like a Tour de France racing bike, to optimize stiffness and weight savings, when it must survive impacts on protruding stones as its rider pushes up and flies down steep winding trails. Instead, its strength and flexibility must be maximized to preserve both bike and rider. Similarly, that road bike now for sale in the bike shops, styled and painted to look for all the world like the racing bike that took the winner's cup available today that offer software platforms that can simulate and optimize fiber architecture and ply shapes that will meet bicycle OEM specifications. Fabio Bressan, manager composite materials and virtual engi- neering for Solvay Composite Materials (Alpharetta, GA, US), affirms that, contending, "e best way is not to build a physical prototype but to build a computer prototype" that simulates the actual product. "Simulation is a special environment where you can increase the complexity of your imagination or the way you want to invent a new design." He sees simulation as a bridge between materials and manufacturing — important because a DeWAL's pressure-sensitive PTFE tapes and films are known for tightly sealing carbon-fiber composites and cleanly releasing parts from molds. Use them to separate epoxy resins from laminates or to seal vacuum bags up to 500°F. DeWAL PTFE tapes and films offer minimal elongation and temperature-resistant silicone-based adhesion. UL-recognized 204-HD films are both skived and tensilized for higher tensile strength, lower elongation and higher dielectric strength. 204-HD films range from 0.5 to 21.5 inches wide and are as long as 108 feet, with tensile strength up to 13,000 psi at 500°F. They are in stock in 2, 3 and 5 mil thicknesses, as are other 36" width DeWAL tapes and films for composites. Whether you are doing open or closed molding, whether your process is lay-up, compression molding, resin transfer or continuous lamination, DeWAL will share a solution with you. DeWAL PTFE Tapes & Films — for tighter vacuum seals and cleaner mold separation. Used as an alternative to sanding and painting Used as peel-ply on molds Used between a mold and a carbon-fiber composite DW 134 DW 204-HD DW 202 & DW 2000 15 Ray Trainor Drive Narragansett, RI 02882 800-366-8356 International: 001-401-789-9736

Articles in this issue

Links on this page

Archives of this issue

view archives of CompositesWorld - SEP 2018