Study On Mechanics Properties Of Epoxy Resin/Glass Fiber Composites

For the advantages of high specific strength, excellent designability, light weight, good fatigue and chemical resistance and low manufacturing costs, etc.,epoxy resin/glass fiber composites have been widely used for the aircraft cabin components, such as floors, wallboards, clapboards, ceilings, baggage liner and cargo liner. As is well known that epoxy resin/glass fiber composites will be exposed to complex weather, it is very important to research the influence of the temperature and humid ageing on the mechanical properties of newly developed epoxy resin/glass fiber composites.The mechanical properties of two types of epoxy resin/glass fiber composites named Repreg-7020 and Repreg-7030 have been investigated at different temperature by tensile test, compression test, bending test, interlaminar shear strength test and longitudinal and transverse shear test and main results are obtained as follows:The dry strengths and wet strengths of two types of composites, including tensile strength, compression strength, bending strength, interlaminar shear strength and longitudinal and transverse shear strength, decrease with increasing of the temperature, so are dry tensile modulus and dry flexural modulus. The dry compression moduli firstly increase and then decrease with the temperature and reach their maximum at room temperature, whereas the dry longitudinal and transverse shear moduli firstly decrease and then increase with the temperature and reach their minimum at 71℃. After wet processing, the mechanical properties two types of composites decline in a varied degree compared to those of dry state and the reducing degrees become large with increasing of the temperature.With the same test temperature, the strengths and moduli of tensile, compression, longitudinal transverse shear of Repreg-7020 are higher than those of Repreg-7030 in both dry and wet state. The dry bending strengths and moduli of Repreg-7020 are higher than those of Repreg-7030 and the wet bending strengths and moduli of Repreg-7020 are much higher at room temperature and slightly higher than those of Repreg-7030 at 71℃ and 93℃. The interlaminar shear strengths of Repreg-7020 are higher than those of Repreg-7030 and the difference become small with increasing of temperature and they are almost equal at 93℃.SEM observations on tensile and compression specimen fracture indicate that at low temperature resin and glass fiber are closely combined and fibers are pulled out in the form of fibrous bundle. With the temperature increasing or treated by wet processing, fibers are pulled out with a little resin adherence and during the tensile test fracture a single fiber is pulled out. SEM observations on the macrofractures of bending, interlaminar shear and longitudinal and transverse shear specimen reveal that at low temperature bending fracture occurs on the lower surface and interlaminar shear fracture is in the middle of the specimen. Longitudinal and transverse shear fracture is relatively flat and the fibers unplugged are very short. With increasing of temperature bending and interlaminar shear fractures are across the cross section and longitudinal and transverse shear fracture shows distinct necking with layered fibers and the fibers unplugged become longer.