The Case Study of a Brittle Failure of a Mountain Bike Frame Composed by Carbon Fiber Reinforced Plastic

A mountain bike carbon reinforced polymeric frame failed in two pieces during cycling over a grass meadow at a speed of about 25 km/h. This has caused the shoulder dislocation of the driver, also last author of this paper. Here, we demonstrate evidence of macroscopic numerous pre-existing and propagating defects, such as wrinkles, voids and delaminations, resulting in low mechanical properties of this frame. Numerical dynamic simulations conclude the paper and suggest a further cause of frame weakening, due to defect-resonance interaction. The paper suggests that the design of carbon fiber reinforced plastic frame for mountain bikes may require new scientific and technological advancements for the safety of the riders, at least today carefully eliminating pre-existing defects and tomorrow proposing bioinspired flaw tolerant solutions.