Study On Mechanical Properties Of Nacre-like Composite Structure

In nature,many biocomposites have extremely excellent mechanical properties,among which shell nacreous layer has attracted the attention of many scholars due to its unique staggered structure,high stiffness,high strength and high toughness.In order to improve the strength and toughness of the material,the researchers were inspired by the natural nacre structure and used the bionic way to prepare the composite material with high strength and high toughness.However,due to the influence of the preparation process and the environment,it is difficult to avoid introducing different geometric parameters and material parameters into the microstructure,which is bound to have a certain influence on the overall modulus,strength and toughness of the structure.This paper applied the imitation pearl layer structure equivalent modulus theory model and combined with the finite element method analyzes the modulus of soft phase and hard phase length-width ratio,the overlap ratio,the structure of the volume fraction of the whole the influence of modulus of elasticity,the results show that soft phase had a greater influence on the modulus modulus on the whole,and modulus of soft phase is lower than 20 GPa,affect significantly;When the length-width ratio increases,the equivalent modulus of the structure increases.As the volume fraction of the hard phase decreases,the equivalent modulus of the structure decreases.When the volume fraction of the hard phase decreases from 0.95 to 0.2,the modulus decreases by 75.6%,and the volume fraction of the hard phase has a great effect on the equivalent modulus of the structure.The overlap ratio has little effect on the structural modulus.Secondly,the tensile crack propagation model of nacre-like structure was established.The cohesive force model is introduced to simulate the interlaminar damage and crack propagation of nacreous structures.The effects of length-width ratio,overlap ratio and randomness of hard phase on tensile strength and toughness were analyzed.The results show that the length-width ratio and the overlap ratio have great influence on the tensile strength and toughness of the structure.With the length-width ratio and the overlap ratio increasing,the tensile strength and toughness of the structure increase.With the increase of the randomness of the hard phase,the tensile strength and toughness of the structure decrease,and the decrease of toughness is more obvious.Compared with the ideal structure,the tensile strength and toughness of the structure with the randomness of 0.025 decrease by 13%and 27.3%.In addition,the fiscal-cracking model is introduced to analyze the influence of interfacial strength on the tensile strength and toughness of the structure.The results show that with the increase of interfacial strength,the tensile strength and toughness of the structure first increase and then decrease,and the optimal interfacial strength exists.Finally,a three-point bending model of nacre-like structure was established to analyze the effects of length-width ratio,overlap ratio and randomness of hard phase on the bending performance of the structure.The results show that with the increase of the length-width ratio of the hard phase,the bending strength of the structure increases significantly.With the increase of overlap ratio,the bending strength of the structure increases.When the random degree increases,the bending strength of the structure decreases.In addition,the Nacreous layer structures with different length-width ratios were prepared by 3D printing method,and the three-point bending test was carried out.It was found that the bending strength increased with the length-width ratio increasing,which was consistent with the simulation results.The failure morphology of the two structures was similar.