Effect of post-curing on thermal and mechanical behavior of GFRP composites

Abstract

Curing cycle has a strong impact on the thermal and mechanical behavior of thermosetting polymers. The extent of cross-linking which is a strong function of curing temperature and time is directly linked to the glass transition temperature (Tg) of the thermosetting polymer. This transition temperature speaks about the transformation of the polymer from glassy state to rubbery state, hence decides the applicability of the material at certain temperature with

certain degree of safety and reliability. Hence assessment of Tg and its possible improvement is quite essential from material point of view. The present study is emphasized on the impact of post curing parameters on thermal as well as mechanical behavior of glass fiber reinforced polymer (GFRP) composite. Post curing was carried out at 3 different temperatures (80°C, 110°C and 140°C) for different time periods (2h, 4h, 6h, 8h and 12h). Short beam Shear (SBS) test was performed on each of the post cured samples to determine the apparent Interlaminar Shear Strength (ILSS) and the corresponding Tg was also evaluated using differential scanning calorimetry (DSC) analysis. The results revealed that the ILSS and Tg are significantly affected with post curing parameters. No significant change in both ILSS and Tg was obtained at 80°C over the entire curing time. At 110 °C both ILSS and Tg improve steadily with a very lower rate even upto 12 hrs of curing and at higher temperature (140 °C) the rate of increment in ILSS and Tg is quite rapid at initial stage and both ILSS and Tg get saturated after 6hrs of curing. With all the possible combinations of curing temperature and time, optimum values are noticed at 140 °C for 6 hrs.