On the effect of chain stay impact on the structural safety of CFRP structures in mountain biking

Carbon composites (CFRP) are commonly used in mountain bike frames allowing very high stiffness and strength at low weights. But CFRP is also sensitive to transversal impact loads, which damage the material from within and can affect the structural safety. A mountain bike frame suffers from different types of impacts, like crashes and stone impacts as well as contacts of the chain on the chain stay. In rough terrain or by passing obstacles, the chain starts oscillating vertically, on the slack span as well as on the tight span of the drive train. Oscillations with high amplitudes, caused for example by jumps, will lead to impacts of the chain on the chain stay. It is known that recurring impacts damage the surface of the chain stay, but there is only little knowledge if the impact energy leads to considerable damage inside the material, affecting the structures integrity. To analyze the occurring energy levels and to investigate the effect of chain stay impact on the structural safety, a validated multi body model of a Shimano XT drive train was developed in Simpack. The model is activated by vertical excitation based on acceleration measurements in field. This allows the assessment of the energy levels of the impact events as a function of excitation (e.g. track consistence) and drive train parameters (masses, moments of inertia, geometrical dimensions).     «

Carbon composites (CFRP) are commonly used in mountain bike frames allowing very high stiffness and strength at low weights. But CFRP is also sensitive to transversal impact loads, which damage the material from within and can affect the structural safety. A mountain bike frame suffers from different types of impacts, like crashes and stone impacts as well as contacts of the chain on the chain stay. In rough terrain or by passing obstacles, the chain starts oscillating vertically, on the slack s...     »