Structure Evolution and Hoop-Reinforcing Mechanism of Bionic-Inspired Off-Axial Glass Fiber-Reinforced High-Density Polyethylene Pipes Fabricated via Rotating Co-extrusion

Abstract

Triple-layer rotating co-extrusion is employed to fabricate hoop-enhanced polyethylene composite pipes with bionic off-axial glass fiber (GF)-reinforced high-density polyethylene (HDPE) middle layer. One kind of super-“hybrid shish-kebab”-like structures formed by GFs and interfacial lamellae tend to spirally align with a fiber deviation angle of 55.7° as the rotation rate reaches 20 rpm. Encouragingly, the hoop strength and hydraulic damage resistance are improved by 25.5 and 24.1%, respectively, even with a low fiber aspect ratio, which can be attributed to the enhanced hoop loading capacity and the energy dissipation effect of crack bifurcation contributed by deviated hybrid structures. Innovatively, the relationship between processing field and structure evolution has been systematically investigated by the simulation of melt flow track, shear rate, and flow rate, indicating that fiber deviation is closely related to the shear rate. This work develops a feasible strategy with both academic value and industrial application prospect for the hoop enhancement of fiber-reinforced HDPE pressure pipes and improves its adaptability to service requirements as well.