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NEWS 41 Bicycle Design Integrity in last year's Big Race, must be beefed up and can't weigh as little as its namesake if it is to survive thousands of miles of sometimes rough pavement, when that similar-looking championship bike was expected to perform in but a single race series. Further, any structural defects, especially at removable part joints, reduce stiff- ness and strength in the regions of the defects and affect not only performance but rider safety. Steps must be taken to prevent such defects and provide for adequate manufactured part inspection. Design tools Among other simulation platforms, Bressan has used Hyper- Mesh, a HyperWorks product from Altair Engineering (Troy, MI, US). Jeffrey Wollschlager, Altair's senior director, composites technology, explains that Altair "took topology optimization tech- nology that was originally developed for isotropic metals and adapted it to direc- tional composite anisotropic materials." Its multi-scale simulation features reach down to design levels of individual fiber and resin constituents, allowing the designer to "design-tune not only the structure but also the material," as well as offer manufacturing simulation capability that enables the user to simulate draping individual plies onto the tooling, he says. HyperWorks is used by Argon18 "to reduce cost and time during the develop- ment of a bike frame," says Legay (Fig. 1, p. 37). "It allows us to develop optimized products that we could not get by test and trial-and-error only." e HyperWorks platform also was successfully used by composite bike design specialist Gridlayer LLC (Denver, CO, US) in the design of the Alfa all-road bike for Allied Cycle Works/HIA-Velo (Little Rock, AR, US) (Fig. 2, p. 39.) "A composite bicycle must ride great and provide adequate comfort for the rider while meeting safety standards. Hyper- Works allows us to optimize and verify the laminate design long before material or tooling is cut," says Gridlayer founder and owner Chris Meertens. "Once tooling is made, you are locked in." (Fig. 3, p. 42.) Another design software choice for composite bicycles is Collier's Hyper- Sizer. Computer-aided engineering (CAE) software that couples with finite element analysis to analyze and optimize structures, HyperSizer is a NASA-spinoff software originally conceived for the aero- space industry. (Fig 4, p. 46.) Material selections ese design factors and solutions guide selection of the best materials for the bike's purpose. Materials suppliers provide the tested property values of their products, which then can be entered into design software at the constituent, raw materials level. But it's also necessary to determine the strength of the cured part, through coupon testing, which is the next design level after individual fiber/resin constituents. Stier says, "So far, the unchallenged frontrunner for composite high-performance bikes is unidirectional (UD) carbon fiber combined with epoxy thermosets in their various combinations." WANTED: your toughest composite challenges We make composite parts no one else can. Visit us in Booth R29

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