Self-reporting damage and enhancing interfacial properties of carbon fiber composites via self-assembly host-guest mechanochromic fluorescent probe

Structural health monitoring (SHM) of carbon fiber reinforced polymer (CFRP) composites under dynamic or static overloading was essential to assure safety and service life. Herein, perylenediimides-gamma Cyclodextrins (PDI gamma CD) inclusion complex was first designed by self-assembly host-guest method and used as mechanochromic fluorescent probe to construct a novel carbon fiber (CF@PDI-gamma CD) interphase, and the interfacial self-reporting damage as well as interface property and reinforcing mechanism of CFRP composites were investigated. PDI-gamma CD was tailored by N.center dot center dot O-H hydrogen bonding between PDI and the cavity of gamma CD, and the fluorescence switching on of PDI-gamma CD was observed under mechanical force. The chemical activity and roughness of CF@PDI-gamma CD surface were increased. The CF@PDI-gamma CD surface exhibited slight fluorescence instead of non-fluorescence on CF-pristine and CF-commercial surface, and the green fluorescent change in the interfacial regions was monitored due to the mechanochromic switching-on of PDI-gamma CD, indicating the micron-scale damage of CF@PDI-gamma CD composites. The interfacial shear strength (IFSS) of CF@PDI-gamma CD composites was much higher than that of CF pristine and CF-commercial composites, which was attributed to synchronous enhancement of mechanical interlocking and chemical bonding between PDI-gamma CD and epoxy matrix. Consequently, this work presented a potential application in synergistically monitoring damage and enhancing interfacial properties of CFRP composites.