Investigations Into The Multiaxial Mechanical Behavior Of Periodic Closed-Cell Foams Printed Using FDM Technology

As a class of extraordinary lightweight energy absorption materials,Kelvin and Octet-B closed-cell foams have been widely applied under multiaxial loading conditions in engineering.For this reason,it requires to gain thorough understanding of their multiaxial mechanical characteristics in a practical manner.This study aims to develop a realistic finite element analysis(FEA)model for investigating their uniaxial,compression-shear,and triaxial compression performance under multiaxial loading conditions.The aim is to establish the relationship between the meso-models of foam and the macroscopic mechanical properties.The main conclusions as follows:(1)Four key printing parameters in the FDM process,such as the temperature of the printing nozzle,the layer thickness,the filling rate and printing rate,are selected as the influencing factors.Based on the Taguchi method,the orthogonal experimental design,signal-to-noise ratio analysis and variance analysis are used.Aiming at obtaining the optimal tensile properties of the foam matrix material,a set of optimal printing parameter combinations were getted.(2)Based on the obtained optimal printing parameters,the foam samples were printed and loaded by uniaxial compression.Verfied by the experimental results,the uniaxial compression finite element simulation analysis of Kelvin and Octet-B foams was carried out.It is shown that the relative density has a dominant effect on the mechanical responses.The deformation mode of Kelvin foam is greatly affected by density,while Octet-B foam hardly changes.(3)The numerical simulation studies of Kelvin and Octet-B foams under compression-shear loading were conducted.The results show that the normal stress of the two foams decreases with the increase of the loading angle,while the tangential stress shows oppositely.Both of them increase positively with the relative density.The deformation of the two foams is close to 0°pure compression when loaded at 15°;A more uniform deformation appears when loaded at 45°and“H”shape deformation mode comes out under 75°loading.(4)Asymmetric triaxial loading simulations of Kelvin and Octet-B foams were carried out and the initial yield data were depicted in the von Mises stress σ_eb and mean stress σ_m plane.Normalized by the uniaxial yield stress,the initial yield surface of Kelvin foams with 20%and 30%relative densitiest can be better characterized by the Miller criterion,which with 10%relative density is more suitable for the yield function proposed by Zhang et al.For the Octet-B foam,the Deshpande-Fleck yielding model has higher fitting accuracy.