Rmvgk Rao

Postcuring Effects on Impact Behavior of Glass/Epoxy Composite Laminates

Studies had been undertaken on the effects of different postcure schedules on the impact resistance of RT-cured glass/epoxy laminates, subjected to repeated drop tests using an in-house built uninstrumented drop weight impact tester. The impact resistance was assessed in terms of two parameters, viz., the number of drops to failure (Nf) and the delamination area growth (dA). The specimens were postcured at different time-temperature combinations and the impact response was studied at three different incident energy levels (10.6, 12.6, and 14.8 J). It was found that, the Nf and dA values increased to a maximum at an optimum postcure schedule of 85 C/4 h. The extent of composite cure for the different postcure schedules was ascertained by measuring the glass transition temperatures (Tg), in order to obtain an appreciation for correlation between the impact resistance and the chemical cure status of the composite. Also, single drop impact studies were made at the 25-J energy level using an instrumented impact tester (DYNATUP 8250) and the aforesaid optimum postcure schedule was reconfirmed.