Experimental Characterization of Shape Memory Polymer Enhanced Thermoplastic Self-Healing Carbon/Epoxy Composites

摘要

Self-healing composites are polymeric composite materials that have embedded healant polymers, which can heal the micro and macroscopic damages by autonomous fashion or through external intervention. For external intervention type of self-healing reported to date, it was either unaddressed or achieved manually. In this study, in-situ, biomimetic, close then heal type of self-healing was implemented to heal delamination damage in carbon fiber reinforced polymer (CFRP) matrix composite. In the studied self-healing scheme, a blend of thermoplastic polyurethane based shape memory polymer (SMP) and polycaprolactone (PCL) was utilized with the thermosetting epoxy as the healant, while the in-situ triggering (heating) was implemented by the macro fiber composite (MFC). The SMP and PCL mixture exhibits a combination of shape memory (SM) assisted healing response, where SMP assisted in closing the cracks upon heating above (80°C) its glass transition temperature (Tg) (55°C) while PCL chains tackify the cracked surfaces by melt (melting temperature, Tm=55~58°C) diffusion to the free surface and ultimately across the area of damage during the same heating. We found that the optimum thermal actuation time via localized heating through the MFC is 30 minutes. The localized MFC actuated healing showed a significant improvement in healing efficiency, which is determined based on the Mode-Ⅰ interlaminar fracture toughness. Specimens with MFC actuated healing showed almost complete healing, as healing efficiency relative to virgin fracture toughness of up to 146.42% was obtained. Fractography analysis was carried out to characterize the fracture recovery pattern of CFRP composite by optical microscope. The change in material properties of the thermosetting epoxy due to the addition of the thermoplastic healants was also investigated via Fourier transform infrared (FTIR) spectra and Differential scanning calorimetry (DSC).