In this study, behavior of polymer specimen and composite specimen on room temperature and high temperature was investigated. Polymer specimen(Epoxy specimen) was made with improved high-temperature epoxy resin as the main material for applying to high temperature environment in teflon mold. and composite specimen was made with T800 carbon fiber and high temperature resin(T800/Epoxy) through filament winding process. Single frequency DMA(dynamic mechanical analysis) test, tensile test, and flexural test were performed to evaluate the thermomechanical and mechanical behavior of Epoxy specimen at test temperatures. single frequency DMA test, flexural test, and ILSS test were performed to evaluate the thermomechanical and mechanical behavior of T800/Epoxy specimen at test temperatures.
As results of single frequency DMA test for Epoxy specimen, Tγ, Tβ, and Tg were observed at -29.5℃, 73.4℃, and 278℃, respectively. and the Tβ exists in section of test temperature. Tensile modulus and flexural modulus tend to decrease while test temperature is being increased. and this result is in good agreement with general tendency. In case of failure strain of polymer specimen in 70℃ and 100℃ conditions are decrease in comparison with room temperature condition and failure strain is increased from at 130℃ condition again unlike general tendency. as the result flexural test according to aspect ratio of Epoxy specimen, the ratio of flexural section modulus and shear section modulus Eb/Gb is increased while the test temperature is increased. This result indicates that Epoxy specimen is getting vulnerable at high temperature.
As results of test for T800/Epoxy specimen, phase transition was not observed without Tg due to thermal history. and Tg was observed about at 244℃. Flexural modulus is maintained even temperature condition changed. In the room temperature, compressive fracture was occurred at the top of specimen and crack growed to bottom direction of specimen. And then, tensile fracture was occurred at the bottom of specimen. However, specimen was fractured as interlaminar shear mode by shear force instead of tensile fracture on bottom of specimen, And tensile fracture on bottom of specimen was not occurred at high temperature. Property degradation of polymer and changes of fracture mode cause reduction of flexural strength. Interlaminar shear strength was reduced gradually up to 130℃ condition, and reduced rapidly from 160℃ condition. The brittle-ductile transition and changes of fracture mode were observed at more than 160℃. and those reasons cause the rapid reduction of interlaminar shear strength.
Temperature condition affects bad influence to properties of Epoxy specimen and T800/Epoxy specimen. Phase transition of polymer affects to thermomechanical and mechanical properties especially failure strain of Epoxy specimen. and degradation of polymer causes reduction of flexural strength and interlaminar sheat strength.