Structural Design Of UAV Landing Gear Of Laminated Woven Composite Materials

Landing gear is one of the important parts of light UAVs.It mainly bears the load during take-off,landing,taxiing and parking of the aircraft,and absorbs the impact energy generated when the aircraft is landing or parking on a ship.As an important structural component in the landing gear structure,the leaf spring(buffer)plays an important role in buffering and absorbing the kinetic energy generated when the aircraft is keeping in contact with the ground or the surface of the ship.With the wide application of drones,traditional alloy materials have severely restricted the rapid development of weight reduction and energy saving of UAVs,and new advanced textile composite materials have emerged at the historic moment.2.5D composites are an important branch of three-dimensional textile composites.They have high specific strength,specific modulus and excellent resistance to delamination,bending fatigue,and impact.It has been widely used in aviation,Aerospace.The design and mechanical properties of the 2.5D woven composite reinforcement structure depend on the interlacing of the yarn,the weaving parameters of the reinforcement structure,the geometric model of the woven structure and the basic mechanical properties of the material.This paper closely focuses on the requirements of a certain type of UAV landing gear base,and launches a series of research work based on the meso-material structure design and macro-leaf spring structure design of the leaf spring landing gear.On the one hand,based on the mature 2.5D woven profile weaving and compounding process,a 2.5D woven composite material with warp and interlayer reinforcement is proposed as the meso-structure material of leaf spring landing gear;The mechanical properties of three structural composite materials were compared and analyzed through the mechanical properties experiments of the preform.On this basis,The finite element method is used to further study the elastic properties of microscopic and multi-scale mesoscopic unit cell models with different structures.The validity of different unit cell models is demonstrated.The experimental results of the materials show that the existence of the warp yarns effectively improves the mechanical properties of the composites when the fiber volume content is about 57%.The tensile strength/tensile modulus of 1/3 warp 2.5D composites under longitudinal stretching,compression,bending,in-plane shearing and interlaminar shear loading are1.05/1.09 times and 2.06/1.2 times and 1.61/0.96 times and 1.11and1.94 times and 1.49 times of 1/3 twill 2.5D composites,respectively.The mechanical properties such as tensile,compression,and bending of the composite increase with the increase of the degree of the inclination blinder warp;however,the interlaminar and in-plane shear properties decrease as the increase of the degree of the inclination blinder warp.Among the ordinary warp 2.5D composites exhibits the best tensile,compressive and bending mechanical properties,and its strength and modulus are 979 MPpa and 80.23 Gpa,357.75 MPpa and 70.43 Gpa,692.37 MPpa and 133.26 Gpa respectively.The 1/3 warp 2.5D composites exhibits the best mechanical properties such as in-plane shear and interlaminar shear.The strength and modulus are 246.95 Mpa and 12.35 Gpa respectively,and the interlaminar shear strength is 141.58 Mpa.The microscopic stiffness prediction shows that under the six typical strain loads,the ordinary warp 2.5D composites with high tensile modulus and suitable shear modulus should be selected.As a macroscopic leaf spring structural material with high warp requirements and sufficient bending deformation.On the other hand,based on the meso-structure design and performance research of leaf spring landing gear,the macroscopic theoretical design and strength analysis of the leaf spring structure were carried out by means of the finite element method.The feasibility of the landing gear with leaf spring made of 2.5D woven composites was verified.The results show that the leaf spring with a circular arc shape and a rectangular cross section meets the deflection while the strain is lower than the allowable strain value of the material.On the basis of the width of the leaf spring a=120 mm and the thickness of h=24 mm,the deflection,stress and strain generated by the leaf spring are significantly reduced with the increase of the local thickening length or the local thickening thickness.When the thickness of the thickening is l'=760mm and the thickness of the thickening is h'=36 mm,the deflection,stress and strain meet the design requirements,which proves the rationality of the structural design.