Here are pros of FRP.
Lightweight and high strength. The relative density is between 1.5~2.0, only 1/4~1/5 of carbon steel, but the tensile strength is close, even more than carbon steel, and the specific strength can be compared with higher alloy steel. Therefore, in aviation, rockets, space vehicles, high-pressure containers and other products that need to reduce their weight, they have excellent results. The tensile, bending and compressive strength of some epoxy FRP can reach more than 400Mpa.
Corrosion resistance. FRP is a good corrosion-resistant material, and has good resistance to the atmosphere, water and general concentrations of acids, alkalis, salts, and a variety of oils and solvents. It has been applied to all aspects of chemical corrosion protection and is replacing carbon steel, stainless steel, wood, non-ferrous metals, etc.
Good electrical properties. It is an excellent insulating material used to make insulators. Good dielectric properties can be protected at high frequencies. Microwave penetration is good, and it has been widely used in radomes.
Good thermal performance. FRP has low thermal conductivity, at room temperature is 1.25~1.67kJ/(m·h·K), only 1/100~1/1000 of metal, is an excellent thermal insulation material. Under the condition of instantaneous high temperature, it is an ideal thermal protection and ablation-resistant material, which can protect the spacecraft from high-speed air flow above 2000 ℃.
Good designability. First, various structural products can be flexibly designed according to needs to meet the requirements of use, and the product can have a good integrity. Second, the materials can be fully selected to meet the performance of the product, such as: corrosion-resistant, transient high-temperature resistant, particularly high-strength in a certain direction of the product, good dielectric, etc. can be designed.
Then, how about it’s cons?
Low modulus of elasticity
The elastic modulus of FRP is two times larger than wood, but 10 times smaller than steel (E=2.1E5), so it often feels insufficient rigidity in the product structure and is easy to deform. It can be made into a thin shell structure, a sandwich structure, or it can be compensated by high modulus fibers or reinforced ribs. Long-term temperature resistance is poor. Generally FRP can not be used for a long time at high temperature. The strength of general polyester FRP is obviously reduced above 50 ℃, generally only used below 100 ℃; general-purpose epoxy FRP above 60 ℃, the strength is significantly reduced. However, high temperature resistant resin can be selected to make it possible for long-term working temperature between 200 and 300℃.
The aging phenomenon is a common defect of plastics, and FRP is no exception. It is easy to cause performance degradation under the action of ultraviolet rays, wind, sand, rain, snow, chemical media, and mechanical stress.
Low shear strength
The interlayer shear strength is borne by the resin, so it is very low. The adhesion between the layers can be improved by selecting processes and using coupling agents. The main thing is to avoid shearing the layers as much as possible during product design.
There are basically two major categories, namely wet contact and dry press molding. According to process characteristics, there are hand lay-up molding, lamination molding, RTM method, extrusion method, compression molding, winding molding, etc. Hand lay-up molding includes hand lay-up method, bag pressing method, spray method, wet paste low-pressure method and moldless hand lay-up method.
Post time: Jun-16-2020