Study On Impact And Bending Failure After Impact Of Composite M-stiffened Plates

Carbon fiber composites have special strengths such as high specific strength,high specific rigidity,and designability.Therefore,they have become one of the materials with high priority in the aerospace field.Carbon fiber composite structures are extremely vulnerable to impact damage during use.The impact damage will affect the residual strength of the composite material.This paper mainly studies the damage failure mode of carbon fiber curved plate after impact and the bending failure of composite tension plate with impact damage.(1)Based on the assumption of strain energy equivalence of the continuum damage theory,the stiffness matrix of the composite after damage is derived.The three-dimensional Hashin criterion is used to judge the failure of the element,And the damage stiffness reduction factor controlled by the element stress at failure and fracture toughness of materials is built.The finite element models of composite curved panel subjected to low speed impact are established,The composite curved panels with various structural angles are studied,which are subjected to impact from inside or outside.The effect of the angle of the curved panel and the impact direction on the laminated curved panel with the same impact energy is investigated.(2)Based on the above impact methods,a low-speed impact finite element model of a composite stiffened plate is established.The defect preset method is used to simulate the bending of a composite stiffened plate with impact damage,The cohesive unit is used to simulate the debonding between the ribs and the skin.The bending load capacity and bending failure mode of composite stiffened plate structure after impact damage are studied.It was showed that:1)The results by the mechanical model based upon the equivalent assumption of strain energy of continuum damage theory are in good agreement with those in the literature.The effectiveness of the model is verified.2)Under the same impact energy,the damage degree of composite curved plate structure is more serious than that of composite plate structure.3)For impact on either side,in the case of acute angle,the smaller the angle,the greater the degree of damage.At right angles the degree of damage is minimal.In the case of obtuse angle,the degree of impact damage is between the acute angle and the right angle.At the same structural angle,the degree of damage occurred when impacted by the inside is higher than that of the outside.4)When a composite stiffened plate is subjected to a bending load,impact damage at two different locations has little effect on the bending load carrying capacity of the composite stiffened plate.