Sandhya Rao

Studies on Tensile and Interlaminar Shear Strength Properties of Thermally Cured and Microwave Cured Glass–Epoxy Composites

Experimental studies are carried out on two different glass–epoxy composites (one room temperature curing epoxy–amine system and the other, an elevated temperature curing epoxy–amine system) subjected to two different curing techniques (thermal and microwave), in order to investigate the effects on their thermomechanical properties. Microwave (MW) curing is carried out using a laboratory scale, custom-built, multi-mode microwave cure chambery operating at a frequency of 2450 MHz. Tensile and interlaminar shear strength (ILSS) properties of the MW cured composites either compared well, or were superior, to those of their thermally cured counterparts, offering the added advantages of reduced cure cycle time, uniformity of cure, and substantial energy savings. Further, the glass transition temperature (Tg) values of MW cured composite laminates are slightly superior to those of thermally cured laminates.

Studies on mechanical behavior of microwave and thermally cured glass fiber reinforced polymer composites

An investigation into the mechanical behavior of microwave-cured glass–epoxy composites is carried out and the results are compared with those of thermally cured composites. Microwave curing of a glass fiber reinforced bifunctional epoxy resin system (LY556/HY951) is carried out in custom-built, multi-mode, industrial microwave cure equipment operating at a frequency of 2450 MHz. Through tensile, compression, and flexural strength tests, it is demonstrated that while the mechanical properties of microwave-cured composites compare well with those of the thermally cured ones, the microwave curing process, per se, results in a significant reduction in the process cycle time and power consumption.

Thermo-Mechanical Creep and Recovery of CTBN–Epoxy Shape Memory Polymers Under Saline Environment

In the present study, the creep and recovery experiments of unmodified epoxy SMP and 5% carboxyl-terminated butadiene acrylonitrile (CTBN) modified epoxy SMPs were carried out after being exposed to saline environment (5% NaCl, 35 °C/98% RH). The creep results of the SMP specimens before and after exposure to saline environment, obtained through short-term tensile creep test at different temperatures (i.e., 25, 80, 103 and 120 °C) and loading conditions, were compared. Prior to exposure to saline environment, the creep strain was found to increase with increasing temperature and reached a maximum around the glass transition temperature (i.e., 103 °C). A higher creep recovery ratio was noticed in the CTBN-modified epoxy SMP particularly at high-temperature conditions. The creep strain was higher in saline environment at 25, 80 and 103 °C; however, at 120 °C both the SMPs could not withstand the applied load. The creep recovery ratio was unaffected by the saline environment in both the SMPs.

Investigations on tensile creep of CNT-epoxy shape memory polymer nanocomposites

In this work, epoxy-based shape memory polymer nanocomposites (SMPnCs) were prepared using 0.5 wt% and 1 wt% multi walled carbon nanotubes (MWCNTs) pre-dispersed in epoxy resin. This was cured with triethylene tetraamine (TETA) curing agent. The glass transition temperatures (Tg) were determined using Advanced Rheometric Expansion System (ARES). The creep behaviour of the 0 wt% CNT SMPnC as well as the 0.5 wt% and 1 wt% MWCNT SMPnCs were studied through short term tensile creep test at different temperatures. Master curves of creep compliance were derived using a time-temperature superposition principle (TTSP) based on Williams-Landel-Ferry (WLF) equation. A Findley power-law model was used to predict the creep deformation behaviour of 0, 0.5 and 1 wt% CNT SMPnCs. Good correlations between experimental data and the predictive model were obtained for both SMPs particularly at lower temperature and above Tg.