How to improve the interlaminar shear strength of carbon fiber composites with high purity bisphenol a type epoxy resins?

In carbon fiber reinforced composites, interlaminar shear strength (ILSS) is a key performance indicator to measure its ability to resist interlaminar delamination, which directly affects the overall load-bearing capacity and reliability of structural parts. Among them, the bonding quality between the resin matrix and the carbon fiber interface area is the core factor that determines the level of ILSS. High purity bisphenol a type epoxy resins play a vital role here. Its extremely high purity significantly reduces the presence of impurities (such as low molecular weight polymers, unreacted monomers or ion residues), which are prone to form stress concentration points or weak interface layers during the resin curing process, becoming the source of crack initiation and expansion, and seriously weakening the interfacial bonding. The use of high purity bisphenol A type epoxy resin can ensure that the cured network is more uniform and dense, greatly improving the cohesive strength of the resin itself and the effective chemical bonding and physical adsorption capacity with the carbon fiber surface, thereby fundamentally strengthening the interfacial bonding.

In addition, the wettability of the resin to the fiber greatly affects the perfect molding of the interface. High purity bisphenol a type epoxy resins usually show better fluidity and lower viscosity characteristics. This characteristic enables it to penetrate into the carbon fiber bundle more quickly and thoroughly during the impregnation stage of composite material preparation, wrap each single fiber, cover the micro defects on the fiber surface, and spread on the fiber surface to form a continuous close contact layer. This excellent wettability effectively reduces defects such as pores and dry spots in the interface area, maximizes the real effective contact area between the resin and the carbon fiber, and lays a physical foundation for the formation of a strong interface layer, which is a necessary prerequisite for improving the interlaminar shear strength.

Furthermore, to obtain excellent and stable interlaminar shear strength, the resin matrix must have good and controllable curing reaction activity. High purity bisphenol a type epoxy resins, with clear molecular structure, precise reaction functional group ratio and extremely low impurity interference, makes the curing reaction process easier to predict and control, and the cross-linking network is more regular and complete. This not only enhances the cohesive strength and modulus of the resin itself, reduces the interlaminar stress concentration and delamination tendency caused by uneven crosslinking density or excessive internal residual stress, but also ensures that the cured resin interface area has better thermal and mechanical stability. Therefore, by using high-purity bisphenol A epoxy resin as the matrix and optimizing its curing process, it is possible to significantly reduce defects and stress concentration in the interface area, and ultimately achieve a substantial improvement in the interlaminar shear strength of carbon fiber composite materials.