Real-time self-monitoring and smart bend recognizing of fiber-reinforced polymer composites enabled by embedded magnetic fibers

Multifunctional composites realized by embedded sensing materials draw much attention to structural health monitoring applications. However, conventional composites are not able to recognize their strain behavior, meanwhile, the embedded sensing elements lack compatibility with host structures and inevitably cause the degradation of the properties. Herein, flexible and micro magnetic fibers (MFs) as embedded sensing units enable conventional composites to possess intelligent self-sensing ability. Combining impedance measurement with mechanical test, the sensing mechanism of MFs is elucidated that the stress-sensitivity of MFs derives from the natural ferromagnetic resonance induced by its intrinsic magnetic anisotropy. The uniaxial tensile and cyclic loading are executed to investigate the electromechanical response ability and monitoring stability of MF monofilament as a sensing element. Then, MFs are embedded into glass fiber (GF) reinforced composites to realize multi-functional MF/GF composites with self-sensing capability, which also do not deteriorate their original mechanical properties. The MF/GF composites inherit high strain sensitivity with a maximum gauge factor of 376, and simultaneously exhibit the ability of bending orientation recognition and damage detection. The MF as a low invasive and embedded functional fiber has great potential to realize self-sensing ability of fiber-reinforced composites, which find particular priority application in pressure vessels and pipes.