The Influence Of Pore On The Mechanical Properties Of CFRP On Hygrothermal Environment

Carbon fiber reinforced polymers composite materials with excellent property have a wide application in the aerospace field, but they affected kinds of environmental factors during storage and use of the process, including hygrothermal environment is frequently encountered environment factors. Under hygrothermal environment, the mechanical properties decreased, which makes the design and use of composite materials more difficult. And because a special molding process, composite materials of internal maybe produce pore defects, it has a undesirable effect on mechanical properties of composite materials with exist of pore defects, hygrothermal environment effects the mechanical properties more serious. Therefore, the research that pore effects the properties of composite under the hygrothermal environment is meaningful.Useing autoclave molding process, preparation of a series of different porosity of carbon fiber/epoxy composite laminates, set different curing stress 0.4, 0.2 and 0.0MPa, porosity ranging from 0.33% to 2%. Using ultrasound A scan and optical microscopy to analysis porosity, pore morphology, distribution, size characteristics. According to HB7401-96, carry on hygrothermal environment and room temperature test, static mechanical properties including tensile properties, compression properties, bend properties and interlaminar shear properties.The results show that: when the porosity increase from 0.33% to 2%, the pore side change from the spherical to elongated shape, and will develop along the layers, the aspect ratio between concentration of 1.54~3.34. After moisture saturated, show layer cracks, crack caused by pore and expanded. Laminate's moisture follows the linear relationship of M i and t 12 on the initial stage, and later absorbence deviate from the linear relationship. Saturated moisture content and diffusion coefficient increase with increasing porosity; the time of moisture reach the saturation increases with the porosity increased slightly; Sample size affect the equilibrium moisture content and diffusion coefficient.The tensile strength and modulus fluctuate during the increase of moisture absorption time, and decline at last. The properties of bend, compress and interlaminar shear decline during the moisture absorption time. As pore rate increases, tensile strength falls 6.5%, 2.5% and 1.2% respectively, Tensile modulus after moisture saturation is basically unchanged; After saturation, compress strength falls 14.6% and 20.5% respectively; Bend strength falls 13.3% and 18.7% respectively; interlaminar shear strength falls 19.7%,27.4% and 35.2% respectively. A little influence on the injuries form of tensile, compression, bending and interlaminar shear, along with the increase of porosity, damage becomes severe. With the porosity from 0.33% to 2%, the tensile strength recovery after drying smaller extent, compression, bending and interlaminar shear strength recovery minimize, were not returned to the room temperature strength.