Abstract
Lattice truss structures, which are used as a core material in sandwich panels, were widely investigated experimentally and theoretically. However, explanation of the deforming mechanism using reliable experimental results is almost rarely reported, particularly for the dynamic deforming mechanism. The present work aimed at the measurement of the deforming mode of lattice truss structures. Indeed, quasi-static and Split Hopkinson Pressure Bar (SHPB) tests have been performed on the tetrahedral truss cores structures made of Aluminum 3003-O. Global values such as crushing forces and displacements between the loading platens are obtained. However, in order to understand the deforming mechanism and to explain the observed impact strength enhancement observed in the experiments, images of the truss core element during the tests are recorded. A method based on the edge detection algorithm is developed and applied to these images. The deforming profiles of one beam are extracted and it allows for calculating the length of beam. It is found that these lengths diminish to a critical value (due to compression) and remain constant afterwards (because of significant bending). The comparison between quasi-static and impact tests shows that the beam were much more compressed under impact loading, which could be understood as the lateral inertia effect in dynamic bucking. Therefore, the impact strength enhancement of tetrahedral truss core sandwich panel can be explained by the delayed buckling of beam under impact (more compression reached), together with the strain hardening of base material.
Highlights
IntroductionCellular materials (such as honeycomb, foam and hollow sphere agglomerate) combining both lightweight and high energy absorbing capacity are widely used in various industrial areas, such as automobiles, naval vehicles, aircrafts [1]
Cellular materials combining both lightweight and high energy absorbing capacity are widely used in various industrial areas, such as automobiles, naval vehicles, aircrafts [1]
Sandwich panel containing honeycomb cores is one kind of superior material comparing with stochastic foams, like CYMAT foams and Alporas foams
Summary
Cellular materials (such as honeycomb, foam and hollow sphere agglomerate) combining both lightweight and high energy absorbing capacity are widely used in various industrial areas, such as automobiles, naval vehicles, aircrafts [1]. Sandwich panel containing honeycomb cores is one kind of superior material comparing with stochastic foams, like CYMAT foams and Alporas foams. Most commercial honeycomb core panels are difficult to fabricate into complex curved shapes because of induced anticlastic curvature, and they trap moisture leading to internal corrosion and facesheet debonding due to their close-cell structure (indicated by Sypeck 2005 [2]). As an open cell periodic structure, lattice truss core structure can exploit to multifunctional applications, for example, heat exchange media [3]. It can decrease the relative density of the structures to several percents. Lattice truss core structure is supposed to be a promising substitute
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