Numerical Simulation And Experimental Study Of A Unidirectional Basalt Fiber Helical Composite Spring

With the development of lightweight vehicles,higher requirements have been put on the comprehensive performance of automobile parts.The helical spring is an important part to reduce vehicle vibration and shock,but the high quality and poor corrosion resistance of conventional metal helical spring hinder the improvement of the overall performance of the vehicle.Therefore,polymer-based fiber reinforced helical composite springs have attracted widespread attention for their excellent specific stiffness,specific strength and good corrosion resistance.This article used a combination of finite element and experimental tests to study a unidirectional basalt fiber helical composite spring.Through finite element simulation,the size of the spring medium diameter and the size of the spring pitch were obtained when the compression performance reached the optimal under the spring wire diameter of 12 mm.The compression performance of the helical spring under this size was compared with the finite element simulation through experimental tests,and the compression performance of the helical spring at this size was further optimized by changing the structure of the spring wire and adding nano-silica to the matrix.The specific research content of this article is as follows:1.Based on the 12 mm spring wire diameter,helical spring models with different pitches and different middle diameters were established,and the effects of changes in structural parameters on the compression performance of the helical springs were simulated.It is found that the spiral angle of the helical composite spring increases with the increase of the pitch.The smaller the axial deformation under the same compression load,the spring stiffness increases linearly.However,when the pitch is greater than 42 mm,the safety factor of the shear strength of the spring wire is less than the critical value,and transverse failure occurs.As the middle diameter of the helical spring decreases,the bending moment and the curvature coefficient of the helical spring decrease.The smaller the deformation under the same load,the springstiffness increases exponentially.However,when the middle diameter of the spring is less than 90 mm,the safety coefficient of shear strength of the spring wire is less than the critical value,and the failure criterion value of Hashin of the spring wire fiber is higher than the critical value,so the spring wire failure.Therefore,when the medium diameter of the spring is 90 mm and the spring pitch is 42 mm,the unidirectional basalt fiber helical composite spring with the wire diameter of 12 mm has the optimal compression performance.At the same time,the transverse shear modulus and axial tensile modulus of spring wire with different structural parameters remain unchanged,indicating that changing the middle diameter and spring pitch will not affect the modulus of the spring wire.2.Based on the structural parameters optimized by the finite element method,the unidirectional basalt fiber helical composite spring with the same structural parameters and the helical spring wire rod were made by experiment,and tested for performance.The stiffness of the helical spring,the relationship between the transverse shear stress and strain of the spring wire and the axial tensile stress-strain relationship of the spring wire were analyzed respectively,and compared with the finite element results.By applying the same compression load as the finite element,the average spring stiffness and average compression displacement obtained from the tests were 4.74 N/mm and 50.82 mm,respectively.And the errors are 11% and 2.9%compared with the finite element results.And there is no failure of the helical spring under the maximum compression.The spring wire gradually fails under the action of shear force,but when it reaches its axial tensile limit,it appears as a sudden brittle fracture.The average shear modulus and average tensile modulus of single fiber resin rod were 7.59 GPa and 33.63 GPa respectively,and the errors were 10.14% and2.88% respectively compared with the finite element results.Therefore,the simulation analysis of the compression performance of unidirectional basalt fiber helical composite spring is reasonable.3.In order to further increase the stiffness of helical composite springs,based on the optimized structural parameters of finite element analysis,and using the bionic idea to imitate the unique structure of collagen,experimentally prepared helicalcomposite spring wire with two and four fiber bundles braiding each other.The test results show that the stiffness of the helical spring is 6.67 N/mm and 7.46 N/mm respectively.Compared with the unidirectional fiber reinforced helical composite spring with unchanged structure,the stiffness is increased by 37.81% and 54.13%,respectively.However,stress concentration and resin enrichment occur at the interweave points of spring wire,which causes the helical spring to easily crack and reduce its fatigue performance.In order to improve the fatigue performance of helical composite springs,basalt fiber helical composite springs with nano-silica particles were prepared.When the content of nano-silica is 0.4 wt%,the compression performance of the helical spring is the best,its spring stiffness and fatigue performance are 52.1% and 43.5% higher than that of helical springs without nano-silica modification.The improvement in performance can be attributed to the fact that the uniform distribution of nano-silica improves the interface adhesion between the fiber and the matrix,and reduces the freedom of the fiber.Simultaneously,the interfacial area of the composite material is increased,and the stress is transferred from the matrix to the nano-silica particles.