Effect of PEG-600 Incorporation on the Mechanical and Thermal Response of Tunable Fiber-Reinforced Shape Memory Polymer Composites

Shape memory polymer composites (SMPCs) are an intelligent class of materials capable of self-actuation, offering promising applications in diverse stimuli-responsive material systems. This study developed epoxy-based SMPCs reinforced with carbon-aramid fibers at a 15:85 ratio, with their glass transition temperature (T_g) tailored by incorporating 5 wt.% (SMPC-5) and 10 wt.% (SMPC-10) polyethylene glycol (PEG-600). Dynamic mechanical analysis (DMA) confirmed that PEG addition effectively reduced the T_g from 89.79 °C in the neat composite (SMPC-P) to 70.28 °C in SMPC-5 and 59.34 °C in SMPC-10. Incorporating 5 wt.% PEG enhanced storage and loss moduli, whereas excessive plasticization at 10 wt.% reduced stiffness. Infrared spectroscopy analysis revealed shifts and increased intensities in hydroxyl (OH), aliphatic C-H, and carbonyl (C=O) groups, indicating enhanced intermolecular interactions and bond formation. Tensile testing showed that the carbon-aramid filler significantly improved tensile strength and stiffness, with SMPC-10 achieving the highest tensile strength (233.59 MPa) and SMPC-5 the highest Young's modulus (14.081 GPa). These results highlight the complementary role of carbon-aramid reinforcement and PEG plasticization in tuning thermomechanical behavior, providing baseline insights for designing SMPCs with tailored actuation and reliable structural performance.