The material belongs to typical unidirectional fiber-reinforced plastics, where the reinforcing material is usually a type of iodine free or low iodine glass fiber, such as E fiber; The matrix is usually an epoxy resin or a mixture of several epoxy resins. The production of core rods is generally made by impregnating unidirectional glass fibers with epoxy resin matrix and then manufacturing them through continuous extrusion (or pulling) process. According to the process requirements, curing agents, accelerators, and internal release agents need to be added in proportion to the epoxy resin system; At the same time, in order to improve the bonding performance between fibers and resins, coupling agents need to be added for surface treatment of glass fibers; Sometimes other functional additives or fillers are added to the epoxy resin system to meet certain performance requirements, such as defoamers, diluents, and coloring agents.