SEP 2018


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NEWS 47 Bicycle Design Integrity FIG. 5 Thinner, drapable, symmetrical Oxeon AB (BorĂ¥s, Sweden) says its thin TeXtreme spread-tow carbon fiber tapes make it possible to replace a 4-ply UD layup (left) with one symmetrical fabric ply (right) containing the same number of plies but facili- tating much easier drapability on curved surfaces and in tubular constructions. Source | Oxeon/TeXtreme inspection of the part. Although he acknowledges that it is a very expensive procedure, he maintains, "Tomography allows you to check each layer and see what is happening between the materials." "Testing final products by enveloping the structure using a little more than critical design to loads is the current methodology, at least for high-performance bikes," Stier says. Clarifying this state- ment, he explains that a bike is normally designed to handle loads 1.5 or two times greater than those expected. So if the part is loaded for mechanical testing at, say, 1.3 times the design load, and it does not break, "you have proven its structural integrity, which is worth more than analysis, which could always be flawed due to the nature of assumptions," Stier offers. Beckwith, however, questions this method's reliability, noting that in most cases, there is an absence of detailed structural analyses. Loading the part for mechanical testing can induce internal manufacturing voids and delaminations that may UD STF +45/-45 +45 -45 -45 +45

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