Preparation of Small-Diameter Phenolic-Based CFRP Rods Using Multi-Die Pultrusion

This paper introduces a novel multi-die pultrusion system for producing small-diameter phenolic-based CFRP rods. The system consists of multiple short heating dies arranged in series, facilitating the escape of vapor from the die cavities and improving the product quality. The results demonstrate that compared to the traditional dies, the rods produced using the multi-die pultrusion system exhibit higher dimensional stability, and their interlaminar shear strength is mostly above 35 MPa, reaching up to 52 MPa. Compared to the traditional mold, in one instance, its interlaminar shear strength value increased by nearly 71.5%, but in another case, it was only 14.72%. Due to relying solely on one control sample, the results are inconclusive. SEM indicates that the rods produced using the multi-die pultrusion system have fewer voids and better fiber-resin bonding compared to the traditional dies. Additionally, cross-sectional optical microscopy shows that when the pultrusion speed is at or below 0.6 m/min, the impregnation of carbon fibers by phenolic resin is more effective. The proposed multi-die pultrusion system provides a new idea for the production of small-diameter rods. Graphical Abstract