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

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 (T-g) 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 T-g 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 degrees C, 110 degrees C and 140 degrees 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 T-g was also evaluated using differential scanning calorimetry (DSC) analysis. The results revealed that the ILSS and T-g are significantly affected with post curing parameters. No significant change in ILSS was obtained at 80 degrees C over the entire curing time. In case of 110 degrees C a smooth increment in ILSS was observed with time (even till 12 hrs). For samples post cured at 140 degrees C a rapid improvement in ILSS takes place with time followed by saturation. With all the possible combinations of curing temperature and time, optimum values are noticed at 140 degrees C for 6 hrs.