Isothermal epoxy-cure monitoring using nonlinear ultrasonics

Isothermal curing of LY 1564SP resin in an aluminium-adhesive-aluminium laminate is investigated, using a nonlinear ultrasonic immersion technique, to prove its applicability for this type of dynamic material transformation. For verification and comparison, epoxy-cure kinetics and rheological behavior are measured using differential scanning calorimetery (DSC) and dynamic mechanical analysis (DMA). Results reveal that the nonlinear ultrasonics, based on noncollinear wave mixing, can successfully be applied to in situ epoxy-cure monitoring—for example, to adhesive bonds—with reliable detection of gelation and vitrification time instants.