Fiber-reinforced polymers are widely used in automotive and aerospace industries following their excellent strength-to-weight ratio and corrosion resistance. During the operation of components in such application fields, crash loads may occur due to bird strike, hail or accidents during the manufacturing processes. This leads to a necessity of a material characterization under high mechanical loading over short periods of time for the assessment of component safety and reliability. Besides generating characteristic values from impact tests, a suitable method for damage detection and observation of damage evolution during subsequent fatigue loading is mandatory.

To achieve qualified knowledge of impact and residual strength properties, different damage detection methods were compared regarding their level of detail and reproducibility. A special specimen geometry was developed in order to be used in both impact and fatigue testing. The material used is a quasi-isotropic carbon fiber-reinforced polyurethane with symmetrical layer setup [+45/-45/0/90]_2s. The impact tests were carried out at 10, 20 and 30 Joule. The fatigue tests were performed as multiple amplitude tests under tension-compression loading (R = -1) and were monitored regarding the change in dynamic stiffness, temperature and by 3D digital image correlation (DIC).

The damage detection methods were evaluated based on a medium impact energy of 20 J and showed a significant difference between detected areas of up to 63%, whilst presenting the requirement for a separation of damage modes. The fatigue after impact tests presented a decrease in lifetime with increasing impact energies by 18 to 82%. The evaluations of dynamic stiffness and temperature are suggesting that a critical stress level exists, on which the materials shows degradation within one step. Moreover, the DIC-analysis showed significant deformations in out-of-plane direction of the specimen, which makes a 3D-analysis mandatory.