Damage detection of fiber reinforced composite based on mechanoresponsive aggregation induced emission luminogen

Mechanoresponsive luminescence (MRL) have great potential applications in the fields of sensing, displaying, optical information storage and damage detection because of their light emission or color changing response under mechanical stimulation. In this work, 1,1,2,2-tetrakis (4-nitrophenyl) ethane (TPE-4N) has been synthesized as a MRL with aggregation induced emission (AIE) properties. Taking advantage of the high contrast of mechanically sensitive fluorescence of TPE-4N under mechanical stimulation, it has been coated on the various laminated fiber reinforced composites (FRCs) to successfully realize the on-site visualization of stress distribution of composites. V-shear experiments were carried out on three types of laminated FRCs coated with TPE-4N coatings. The experimental results show that TPE-4N can transform the invisible stress distribution information into visible fluorescence information. Moreover, the matrix cracking, fibre fracture and delamination of the composites can be qualitatively analyzed by using the fluorescence visualization images. By considering the repairability of FRC, early warning values were introduced by calculating the fluorescence areas. The fluorescence visualization method proposed in this work demonstrates the great potential in on-site monitoring the structural health condition of engineering composite structures.