Flexural response of glass/epoxy composites to thermal shocks and conditioning environment in varying loading rate

Abstract

The structural integrity of composites faces severe challenge in the form of environmental extremes. Therefore, its performance in those cases were of great interest. In the present work, flexural strength of glass/epoxy composites were analysed in the environment of thermal shock generated by cryogenic exposure as well by thermal conditioning. Four cases were chosen, room temperature (RT), cryogenic conditioning (LN), thermal conditioning below (BG) and above glass transition temperature (AG). The exposure time for all the environments was kept constant at 24 hours. These responses are investigated with two sets of loading rates (i) 1 mm/minute and (ii) 10 mm/min. The experimental results indicate that; all three scenarios deeply impact the flexural response of the specimen. The first set experiences changes in flexural strength, strain, and chord modulus by (2.75, -8.52, 11.32), (21.36, 39.75, -6.47), (-35.8, -11.37, -22.94) % with LN, BG and AG condition respectively. Moreover, with high rate of loading these responses change by (-23.89, -28.41, -5.17), (-37.45, -43.56, -1.86), (-19.4, -27.46, 16.37) % respectively. The prolonged exposure indicates a strain hardening phenomenon in LN specimen, which improves the flexural strength with a 1 mm/min loading rate. However, this plasticization of the specimen was unable to bear the load at an elevated rate of loading, and therefore a loss in all the properties is seen with a 10 mm/min loading rate. Therefore, it is anticipated that the properties will further deteriorate with a higher rate of loadings.