Simulation Analysis Of Mechanical Behavior Of Triaxial Compression Of Flexible Fiber Packings

This paper examines the mechanical response of flexible fiber packings subject to triaxial compression by discrete element method(DEM).The analysis of the mechanical properties of flexible fiber cluster materials under triaxial compression is as follows:(1)A flexible fiber model based on the discrete element method is presented in this work.In this model,a fiber is represented by a chain of sphero-cylinders,which are connected by virtual bonds.Verification of contact force calculation in flexible fiber model by cylinder-cylinder compression test;(2)Measure physical properties such as friction coefficient,Young's modulus,and particle density of the test material in triaxial compression,which is convenient for discrete element simulation of existing test;(3)Perform triaxial compression test of flexible fiber clusters,and simulate the test process,and verify the accuracy of the simulation results through test data.The mechanical properties of flexible fiber materials during triaxial compression are not the same as soil and other loose granular materials.After analyzing a large number of simulation results,the following research conclusions can be obtained: Short fibers yield in a manner similar to typical granular materials in which the deviatoric stress remains nearly constant with increasing strain after reaching a peak value;With the increase of the fiber slenderness ratio,the specimen no longer yields.The axial stress of the sample gradually increases with the increase of the strain;if the fiber aspect ratio continues to increase,long fibers exhibit a hardening behavior,where the stress increases rapidly with increasing strain at large strains and the packing density increases.The positions of boundaries between different regimes depend on the confining pressure and fiber flexibility.The hardening packings can support much larger loads than the yielding packings,but larger internal axial forces within fibers and larger fiber-fiber contact forces occur.The mechanical properties of flexible fiber packings are also affected by test confining pressure,friction coefficient,bending stiffness,and contact stiffness.As the particle friction coefficient and confining pressure increase during triaxial compression,flexible fiber packings are more likely to harden;The elastic stiffness and contact stiffness of fibers have common effects on the mechanical properties of flexible fiber packings.Under the premise that the fiber packings do not yield,the increase in bending stiffness and contact stiffness will make the axial stress increases in triaxial compression.But the increase of the bending stiffness of the fiber causes the stress-strain curve of the flexible fiber clusters to harden.The increase of contact stiffness tends to cause the flexible fiber clusters to yield.