Research On The Strength Of Composite Materials With Voids

Carbon fiber composite materials in aerospace have won extensive application. With advanced composite materials and molding technology development, carbon fiber composite materials also begin to emerge in automobile, manufacturing, construction, shipbuilding and other civil industries. Because of inclusion of air in prepreg, volatilization of redundant solvent, volatiles produced by matrix after chemical reactions and other reasons, the pores were inevitably produced and contained inside the molding materials. Because the porosity have a great effect on mechanical properties of carbon fiber composite materials, it is important to research and analyze the change of composite materials and the porosity's effect on the material mechanics properties.The paper focused on the intensity of composite laminates with different pore content by theories and experiments. Specific research works are as follows:(1)It was introduced that the molding of composite material, the cause of the pore defects and measuring method, especially the experiments and researches on the causes affecting porosity content, and research of the porosity content's effect on the mechanical properties of composite material as well.(2)The effects of curing pressure on the composite laminate and the void content were studied. Ultrasonic attenuation was analyzed by experiment, and the relation between void content and ultrasonic attenuation was established.(3)Finite element analysis model of composite laminate with voids based on homogenization was established. The effect of content and shape of the pores on the tensile modulus of the composite laminate were evaluated by the finite element model. The cumulative damage analysis method and the finite element model were used to calculate the pore content of composite slab tensile strength. It shows that the analysis model and the method are valid by comparing the theoretical result with experiment on the tensile modulus and tensile strength of unidirectional laminate.(4) The static strength of tensile and compression tests were conducted on composite laminate with different void contents. Some mechanical properties, such as tensile modulus, tensile strength, compressive modulus and compressive strength, were obtained by experiment. Meanwhile, it is analyzed that the effect of pore content on the tensile properties and compression properties, and the reasons were discussed in the end.