Condition monitoring of multi-material lightweight components through a sensitive outer skin using Fiber-Bragg-Grating sensors

Multi-material structures for lightweight applications are continuously gaining increased importance, especially in future industries, such as wind power or electro mobility. Material combinations of metal and fiber reinforced polymer (FRP) composites subjected to high or cyclic loads are critical at the interface. The integration of sensors in multi-material components allows for additional functionalities from needs-based maintenance to continuous condition monitoring and fault detection. In addition, the obtained data even further allows the exploitation of the full potential for lightweight design. Inspired by nature and following the concept of Biological Transformation, the technical approach for the implementation of condition monitoring on multi-material components makes use of the periosteum in the endoskeleton of vertebrates as a bionic model. This concept was adopted for metal-FRP multi-material combinations with the integration of Fiber-Bragg-Grating (FBG) sensors within the FRP. By subjecting components to vibration by external excitation, damages in form of delamination were successfully detected by analyzing the state-dependent natural frequencies of the component. Test specimens were prepared and the influence of various parameters such as frequency, location and direction of the excitation as well as the fixture of the samples during excitation on the natural frequency was investigated. The approach was further demonstrated on the example of a component from the sports industry. The chosen snowboard is expected to fulfill lightweight requirements on the one hand while being exposed to irregular high loads.