Study On Crack Blocking Performance Of Aircraft Skin Enhanced By Biomimetic Coupling

Due to the combined action of shear,bending and torsion loads,the aircraft skin is prone to crack on the surface,which leads to the failure of the skin.Considering the existence of a large number of anti-fatigue biological prototypes in nature,a crack arrest method based on the bionic structure of plant leaves for the skin of aluminium alloy aircraft is proposed in this paper.The main contents of this paper are given below:According to the characteristics of the non-linear topological structure of plant veins,we construct a bionic reinforcement structure based on plant leaves for crack propagation retardation.By combining Canny edge operator with Hough transform,a parameter extraction method suitable for main and secondary veins of leaves is established.Then,according to Cantor's three-component rule,bionic residual stress fields with different fractal characteristics of leaf veins are generated at the crack tip of CT specimens.In order to explore the mechanism of crack propagation retardation by biomimetic strengthening of plant leaves,we use the stress intensity factor at the crack tip of CT specimens of 2024 aluminium alloy as measurement index,and then,in view of the distribution characteristics of bionic residual stress field,a stress extrapolation method is used to study the crack retardation effect of bionic structures with different fractal parameters during crack propagation from 2 mm to 12 mm.The results show that the stress intensity factor at the front of the crack decreases effectively after the specimens are strengthened by the bionic residual stress field.This phenomenon reveals the mechanism of the decrease of bionic coupling stress intensity factor caused by bionic structures.When the fractal angle is 45 degrees,the retardation effect of crack propagation is the best,and the residual fatigue life of the structure is increased by 63.16% which show that the proposed method is effective for crack growth retardation.Finally,we take the full-scale aircraft skin as the research object,and simulate the crack growth process by using finite element method.Then we compares the local reinforcement effects of Plant Leaf Biomimetic reinforcement methods on wing with initial defects in this paper.And the local strengthening effect of biomimetic reinforcement of plant leaves on wing skin with initial defects was also studied.The results show that the downward trend of stress intensity factor at the front of aircraft skin crack strengthened by bionic residual stress field is consistent with the simulation results of CT specimens,which further demonstrates the universality of the method proposed in this paper for crack propagation retardation in aircraft skin.