Investigation On Mechanical Properties Of Lightweight Structure Composed Of Hollow Spheres

Cellular materials are known to have many outstanding combinations of physical and mechanical properties. For this reason, cellular materials are currently playing an important role in the engineering applications and scientific technology development. These materials have such important properties that new exciting applications are expected in the near future. The hollow sphere is one of the most basic substructures with well mechanical property and its main failure form is buckling. Hollow sphere foam material, made by sintering or gluing the spheres together, is one of the typical cellar materials. This thesis manily studies the mechanical properties of lightweight structures composed of hollow spheres.This thesis includes four chapters. Chapter 1 gives the basic conception, manufacturing processing, characterization of the cellular materials and a simple review of research on mechanical properties of cellular materials. The emphasis is put on introducing some representative jobs in this field in the foreign countries and our country. Finally, we give the basic structure and research area of the present thesis.In chapter 2, first we give the experimental investigations on mechanical properties of lightweight sandwich beams filled with hollow spheres, including the sandwich beams with a core fabricated either by ping-pong balls or Al₂O₃ hollow spheres. Then we discuss the characteristics of the force-displacement curve of the sandwich beam, and finally give a simple mechanical analysis on the failure of the structures.Chapter 3 gives the compression experimental investigations on the structures of stacking hollow spheres, including the regular arrays of ping-pong balls stacked in a cube lattice and the random arrays of Al₂O₃ hollow spheres bonded by epoxy resin. The force-displacement curve and the deformation of the structures are studied. The failure process of the structure with stacked Al₂O₃ hollow spheres is analyzed.Chapter 4 gives the numerical analysis of mechanical property on a single hollow sphere (ping-pong ball) and the single-sphere sandwich structure under compression using the software system ABAQUS. 2-D axis symmetry model and 3-D half sphere shell model are used for the analysis of a single hollow sphere. 3-D model is used for the analysis of the single-sphere sandwich structure. The force-displacement curve and the deformation are calculated. The analysis results of the single sphere compression under rigid plates are in good agreement with experiments. The calculation force-displacement curve of the single-sphere sandwich structure has the same trend with experiment.