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focus on design able fast fabrication and adapt ing (LRTM) process. Demolded the bi-angle concept to autotubes are mitered, placed in an mated processing. Tsai found a assembly jig and tacked together partner in Michel Cognet, group with high-density structural epmanaging director of Chomarat oxy ���ller. Then the lugs are hand (Le Cheylard, France). The texwrapped, using wet out C-PLY tile specialist now manufactures and woven aramid. Cured frame noncrimp bi-angle fabrics called assemblies are primed and C-PLY, which can be converted to painted. prepregs by Aldila (Poway, Calif.). Eggers reports that there is Brian Laufenberg, president no signi���cant wall thickness difof Chomarat North America (Anference between the original uni derson, S.C.), says conventional prepreg tubes and the infused CFig. 1 Source: Chomarat multiaxial machinery can asPLY tubes: ���The C-PLY���s extreme semble cross plies to about 45��, thinness and light areal weight This diagram, output from MIC-MAC software, shows that but Chomarat���s equipment can shallower cross-ply angles better withstand first-ply failure. results in very light yet very combine 0�� ���bers with off-axis strong tubes.��� plies as acute as 20��. The company���s ef������Using 0�� and ��45�� directions is the Material processing, claims Eggers, cient tow-spreading process can produce ���standard��� layup orientation in carbon is ���dramatically faster.��� Hand layup of fabrics at areal weights as low as 75 g/ bike frames worldwide. Of course we prepreg took 40 hours per frame. Now, m2, and ongoing development is likely tried different angles, including ��25 a frame can be produced with C-PLY in to reduce weight further. Chomarat thus and ��77, as well as all three at the same only four hours. ���There are no problems can provide a complete range of thin, time,��� Eggers recalls. ���We found that with dry spots or voids,��� he adds. Frame low-areal-weight, spread-tow, multiaxial tube breaking strength was the highest testing con���rms better mechanicals and noncrimp C-PLY fabrics. using the ��45 orientation. But, it was riders report a ���better ride.��� The new maC-PLY laminates were ���rst trialed in a real headache for us, and very timeterial ���is a bonus,��� he sums up. ���This has 2010 by Dr. Alan Nettles, a visiting scholar consuming, to produce balanced and really helped our company���s mission of at Stanford. His extensive coupon testing symmetrical layups by cutting 45�� angles producing bikes in the U.S. at a competiunder static and impact loading scenarios manually from uni prepreg tapes. It was tive price ... with autoclave quality.��� showed that infused bi-angle laminates dif���cult to get right.��� He adds that manToday, 23 Carbon EX frame sizes, are virtually equal in performance to uniaging prepreg shipments, freezer storage classed in ���ve stiffness regimes, provide directional prepreg. and out-time increased the dif���culty and a near-custom ���t for a wide range of ridled to wasted materials. ers. Chomarat���s Laufenberg, however, A material change With help from Tsai and Stanford���s expects wider application: ���An unbalAfter discussions with Tsai, Dr. John EggComposites Design Group, the Carbon anced 0��/25�� layup, for example, can take ers, who holds a certi���cate in composite EX frame was reset for the new material. advantage of shear coupling to reduce design from Stanford and is the founder The previous layup involved four unidibending and twisting in wing-type strucand CEO of the nonpro���t cooperative rectional prepreg tape plies (0��/+45��/tures or wind blades.��� Aerospace indusAmerican Artisan Bicycles, converted 45��/0��) inside two-piece tube molds. try curiosity is high. Skillen at VX Aerohis company���s Carbon EX road bike Follow-up analysis by Eggers and the space is reporting good results from frame from prepreg layup to infused CStanford team showed that four C-PLY using C-PLY in some rotorcraft test artiPLY. His team had previously designed layers ��� each a 0�� ply of uni 12K stitched cles and C-PLY is under consideration by the frame using engineering software to a +45�� ply of 12K (both high-strength other airframers, notably Spirit Aerosysprogram Adobe Inventor, supplied by carbon at an areal weight of 79 g/m2) ��� tems Inc. (Wichita, Kan.). Adobe Systems Inc. (San Jose, Calif.), is suf���cient for the top and down tubes. MIC-MAC from Stanford���s Composites Eight carbon plies result in a wall thickLearn More Design Group and bicycle frame-speci���c ness of 0.083 inch/2 mm. To create the @ www.compositesworld.com BikeCAD Pro from The Bicycle Forest Inc. +45�� and -45�� orientations, every other (Kitchener-Waterloo, Ontario, Canada). C-PLY layer is ���ipped. To prevent mold Read this article online at http://short. Intermediate-modulus, 300 g/m2 uni carslippage, plies are secured with tacki���er, compositesworld.com/8937KYrm. bon ���ber prepreg was originally selected reports Eggers. For the seat tube, 10 CRead about efforts to reduce the need for for the top tube, head tube, down tube PLY layers are used (20 total plies) for a conservative design in ���Virtual testing of and seat tube, and woven small-tow fabwall thickness of 0.094 inch/2.4 mm. For composites: Beyond make & break,��� HPC ric combined with a titanium mesh was the head tube, which must withstand November 2012 (p. 36) or visit http://short. selected for the rear triangle (or seat/ compositesworld.com/51EcWxPY. frontal impact, 16 C-PLY layers (32 plies) chain stays). The lugs (tube connections) form a tube wall of 0.145-inch/3.6-mm Tsai and Wu published their failure criterion were made by overwrapping joints with thickness. ���ndings in ���A General Theory of Strength for woven carbon and aramid fabrics; the The layups are infused with West Anisotropic Materials,��� Journal of Composite Materials, 1971, Vol. 5, pp. 58-80. latter was used to improve ���shock abSystem (Bay City, Mich.) epoxy in a sorption,��� says Eggers. heat-assisted light resin transfer mold- 48 | high-performance composites