Influence of curvature on impact damage of strongly curved CFRP-structures

Due to their excellent mechanical properties in relation to weight, CFRP structures are commonly used for high performance sports equipment like bicycle frames. Therefore, especially for mountain bikes, the impact behavior becomes a major issue in development and construction. Impact induced damages can degrade the fiber matrix system locally and reduce its mechanical properties. As defects are often barely visible to the naked eye (BVID), impact damages are critical for structural components. Hence in this study different strongly curved pipe structures are investigated in order to identify the influence of the impact energy on the defect size and the residual strength as a function of curvature. CFRP pipe structures with three different diameters (15, 35 and 50mm) and identical layup ([+45°,-45°, 0°] _s, T700/Epoxy) are systematically impacted using increasing energy levels (5, 10, 15J). To determine the defect size the structures are monitored using pulse echo ultrasonic investigations. Thereafter the residual strength is determined and compared to undamaged structures in a two point bending tests. Therefore the pipes are rigidly clamped on one side, while a bending load is applied in a standard tensile test bench.