Matrix
A composite material is composed of a matrix and reinforcement. First, the role of the matrix is to act as a binder to fix the fibers, transmit stress between the fibers, protect the fibers from the outside, and resist mechanical wear. The mechanical properties of the base material play an important role in the in-plane shear properties and have the effect of inhibiting the buckling of the fibers under compressive stress, but the effect on the resistance under tensile stress is not significant. In addition, in the interaction with the steel material, the proper mixing ratio of the two materials is very important to obtain the desired properties, and the interaction of the two materials is important for the design of damage tolerant structures.
According to the physical principle of fiber reinforced materials, the surface area per unit volume varies depending on the length and diameter of the fiber, and the large contact area between the base material and the reinforcing material facilitates stress transfer and improves mechanical properties.
The types of base materials can be classified as polymer, metal, and ceramic, and polymer resins are divided into thermosetting resins and thermoplastic resins. Currently, polymer composites are mostly thermosetting resins, but in the future, thermoplastics with very good processability are expected to be used. Metal and ceramic base materials are mainly used for high temperature properties. The types of these base materials are shown in the table.
| division | type | |
| Polymer | Thermosetting | Epoxy Polyester, vinyl ester Phenolic Polyimide |
| Thermoplastic | Nylon, Thermoplastic, Polyester (PET, PBT), Polyacetal PAI, PEEK, PSUL, PPS and PEI etc | |
| Metal | Aluminum, titanium alloys, magnesium alloys Stainless steel – for use at high temperatures (300-500°C) | |
| Ceramic | Aluminum Oxide, Carbon, Silicon Carbide | |
Carbon as a base material has a high heat capacity per unit mass, so it is used in rocket nozzles, clutches, and brake pads of airplanes, and its service temperature is 3000°C. Ceramic substrates are generally brittle and are used in extreme environments (high temperatures), with temperatures above 1093-1649°C. Metal substrates are used for high-temperature materials in industry and academia, with a temperature range of 800-1371℃. Polymer base materials are the most commonly used, with low cost, good moldability and mechanical properties, and strong adhesion. The service temperature is below 427℃.