Design of a Pultrusion System for a Hemp-Based Rebar
摘要
Hemp's eco-friendly attributes, prodigious growth, versatility, and excellent mechanical properties make usage of fiber and hurd popular in engineered products, particularly construction materials. Accordingly, this paper presents a pultrusion system for manufacturing yet another construction material: a hemp-reinforced thermoplastic (PP) rebar for use in reinforced concrete. The critical components of the prototype pultrusion system under development are the preform rope (i.e., commingled hemp yarn and thermoplastic filament), a dielectric preheater, a pultrusion die, and a variable speed pulling system. TGA characterization of the constituent materials and testing with compression-molded specimens provide key information for subsequent pultrusion system design. The properties of compression-molded rebar specimens are assumed to be similar to pultruded ones. The first component of the pultrusion system, i.e., dielectric preheating, serves as a quick and efficient method to raise the rebar preform to just below the thermoplastic’s melting temperature, although it is ideally for a polar thermoplastic. Commingled rebar preform rope was tested in a commercial pultrusion preheater to confirm the concept's validity. For subsequent experiments, A conventional convection oven was used for pultrusion experiments. The second component is the converging pultrusion die wherein the heated preform matrix is fully melted and the rebar is consolidated under pressure. Coupled thermal-fluid FEA simulations aided in the construction of the die. The third component consists of peripherals such as an electrical subsystem, speed sensing, a cooling die, and a winch for pulling the rebar through the die. This study proposes a comprehensive rebar manufacturing system feasible for the fabrication of rebar in a factory or at a job site.