Unsaturated polyester resin (UPR) systems are extensively used in composite materials for applications in the transportation, marine, and infrastructure sectors. There are continually evolving formulations of UPRs that need to be evaluated and optimized for processing. Differential Scanning Calorimetry (DSC) provides valuable insight into the non-isothermal and isothermal behavior of UPRs within a prescribed temperature range. In the present work, non-isothermal DSC tests were carried out between temperatures of 0.0 °C and 250 °C, through different heating and cooling ramp rates. The isothermal DSC tests were carried out between 0.0 and 170 °C. The instantaneous rate of cure of the tested temperatures were measured. The application of an autocatalytic model in a calculator was used to simulate curing behaviors under different processing conditions. As the temperature increased from 10 °C up to 170 °C, the rate of cure reduced, and the heat of reaction increased. The simulated cure behavior from the DSC data showed that the degree of cure (α) maximum value of 71.25% was achieved at the highest heating temperature of 85 °C. For the low heating temperature, i.e., 5 °C, the maximum degree of cure (α) did not exceed 12% because there was not enough heat to activate the catalyst to crosslink further.

Sheet Molding Compound (SMC) is a widely used composite material, particularly in automotive applications, due to its cost-effectiveness, lightweight properties, and adaptability for complex shapes. While E-glass is commonly used as reinforcement in SMC, its strength and stiffness are limited compared to carbon fiber (CF). Previous research has focused on continuous-discontinuous SMC hybrids, combining continuous CF with glass fiber substrates, but these approaches are costly and complex to manufacture. This study explores a novel discontinuous-discontinuous hybrid SMC that combines E-glass SMC (G-SMC) with recycled carbon fiber (rCF) mats, aiming to enhance mechanical properties without a significant cost increase. Two materials were produced, one with and one without rCF, and were tested for flexural, tensile, interlaminar shear, and impact properties. Failure mechanisms were also examined through digital imaging. This approach demonstrates the potential for a cost-effective and practical SMC hybrid suitable for commercial applications in the automotive industry.

Traditional sandwich composite panels consist of stiff facesheets that support bending loads and a core that bears shearing load. In this study, the core and facesheet were assembled in a single process to eliminate the possibility of delamination between the layers, and make the structure unitary in its construction. The drop tower impact test was conducted in accordance to ASTM standard D7136 to evaluate the impact strength of the panels while taking into consideration the impact velocity and the coefficient of restitution. The impact velocities used were 1 m/s and 4.6 m/s denoted as V 1 m s and V 4.6 m s respectively. A Phased Array Ultrasonic Testing (PAUT) inspection was conducted to evaluate damage extent in the high velocity samples. At V 4.6 m s , the CoR ranged between 0.05 and 0.363, suggesting some amount of elastic collision. The displayed Energy Loss Percentage (ELP) was more than 85%, suggesting that the specimen experienced total perforation. There were mainly dents on the front side and bulges on the opposite sides of the specimens tested at V 1 m s while at V 4.6 m s , the specimens experienced considerable damage including perforation. Ultrasound (UT) inspection of the damaged specimens did not show delamination. Avoiding dislocation of structural members when manufacturing composite panels for intermodal containers and truck beds was achieved.