The heat resistance of FRP is different for different substrates. you can find the heat resistance range of FRP corresponding to various resins through the data, but do you know why different resins have different heat resistance levels?
The heat resistance of FRP is manifested in that as the temperature increases, the mechanical properties of the resin matrix (such as bending strength and modulus, shear strength, etc.) will gradually decrease, resulting in a decrease in the overall mechanical properties of FRP. Fundamentally speaking, the degree of heat resistance of glass fiber reinforced plastic mainly depends on the resin matrix. After all, the temperature resistance of ordinary glass fiber is as high as 350°C, which is generally more heat resistant than the matrix. Theoretically, the heat resistance mechanism can be summarized into the following aspects:
1. The theory of molecular bond weakening
As the temperature increases, the molecular bonds of the matrix and the interface will weaken, and the kinetic energy will increase, which may cause some bonds to break under a certain load.
2. Microcrack theory
Due to the difference between the thermal expansion coefficient of the fiber and the matrix, as the temperature rises, thermal stress is generated, and microcracks are prone to occur. At the same time, during the curing process, there are bubbles or impurities in the matrix to form defects. After the temperature rises, the air expands by heat. , Increase the formation of cracks, these will reduce the mechanical properties of the material to some extent.
3. Resilience theory
The matrix has a certain inhibitory effect on fiber defects, which can limit the fiber damage area from no longer expanding. As the temperature increases, the matrix toughness becomes larger, and the fiber inhibition weakens, the damage area will expand, and the strength will correspondingly decrease.
Combining the above heat resistance mechanism, then, what are the ways to improve the heat resistance of FRP?