Process parameters of glass-fiber-reinforced vinyl ester/nano-Al ₂ O ₃ matrix composites for pultrusion

Unidirectional glass-fiber-reinforced vinyl ester composites containing nano-Al ₂ O ₃ were fabricated using the pultrusion process. This study investigates the optimal processing parameters and their effects on the composite’s properties, focusing on die temperature, pulling rate, postcuring conditions, filler content, and glass fiber content. Differential scanning calorimetry (DSC) analyses were employed to determine the optimal die temperature by assessing the degree of cure in the pultruded composites. An increase in pulling rate was observed to correlate with a decrease in mechanical properties, highlighting the necessity of balancing these parameters. Appropriate postcuring temperatures and durations were found to enhance the mechanical properties of the composites. However, extended postcuring times led to property degradation, or over-curing of the resin matrix. The incorporation of nano-Al ₂ O ₃ at 2 parts per hundred resin (phr) and a glass fiber content of 75.6 vol% resulted in peak flexural strength and notched Izod impact strength. Beyond this filler concentration, a decline in these properties was noted, possibly due to agglomeration of nanoparticles or compromised fiber–matrix interactions. Conversely, the flexural modulus and hardness exhibited an increase with higher nano-Al ₂ O ₃ and glass fiber content, suggesting enhanced stiffness and surface hardness. The addition of nano-Al ₂ O ₃ contributed to reduced shrinkage in the pultruded composites, resulting in smoother surface finishes. This improvement is attributed to the nanoparticles’ ability to restrict matrix contraction during curing. In summary, meticulous optimization of pultrusion parameters and filler content is crucial for achieving superior mechanical performance and quality in glass-fiber-reinforced vinyl ester/nano-Al ₂ O ₃ composites.