Study On Dynamic Mechanical Properties Of Carbon Fiber Woven Composites

Carbon fiber reinforced resin matrix composites(CFRP)are more and more used in various engineering due to its advantages of light weight and high strength.Compared with traditional laminated composites,three-dimensional(3D)woven composites have higher impact damage tolerance and anti delamination ability,are widely used in aerospace automobile and other fields.In the application process,the impact load is inevitable.Therefore,the study of dynamic mechanical properties and damage failure mode of 3D woven composites under impact load has important reference value for the development of composite application.In this paper,the dynamic mechanical properties of 3D woven composites and its constituent materials,including unidirectional carbon fiber and matrix resin,were experimentally studied.Firstly,the dynamic compression tests of unidirectional carbon fiber along the fiber direction(1 direction),vertical fiber direction(2 direction)and matrix resin were carried out by using different types of split Hopkinson pressure bar(SHPB)test system.The compression stress-strain curves of the material under different strain rate loading were obtained.It was found that the dynamic compressive strength of carbon fiber in 1 direction was much greater than that in 2 direction,and the mechanical properties of carbon fiber in 1 and 2 directions had strain rate effect The dynamic compressive strength in the direction 1 increases first and then decreases,while the dynamic compressive strength in direction 2 increases monotonically with the increase of strain rate.The dynamic compressive strength of the resin increases with the increase of strain rate.The failure strain of carbon fiber and resin decreases with the increase of strain rate.The 2d-dic(2D digital image correlation)technology is used to analyze the failure mode.Secondly,the dynamic tensile test of matrix resin was carried out by split Hopkinson tensile bar(SHTB)test system.It was found that the tensile strength of the resin was less than its compressive strength.The dynamic tensile strength of the resin increased with the increase of strain rate,and the failure strain decreased with the increase of strain rate.The surface deformation and failure process of the specimen were obtained by 2d-dic technology.It was found that the failure mode of resin in tension was different from that in compression.Finally,the in-plane and out-of-plane dynamic compression experiments and inplane dynamic shear experiments of the 3D woven composite material were carried out using the 40 mm SHPB test system with different lengths.It was found that the out of plane dynamic compressive strength strain rate effect was not obvious,the dynamic compressive strength did not change with the change of loading strain rate,and the failure strain decreased with the increase of strain rate.The effect of strain rate on the in-plane dynamic compression and shear mechanical properties was not obvious.With the change of the loading strain rate,the in-plane compressive strength,shear strength and failure strain of the material have no significant changes.In addition,this paper improves a medium strain rate test technology,By improving the traditional 40 mm Hopkinson pressure bar,a set of 40 mm Hopkinson bar medium strain rate impact test system was formed,and completes the dynamic compression test of 3D woven composite matrix resin.