Study On Mechanical Properties Of Wood-Based Triangular Prism-Type Lattice Sandwich Structure

Compared with raw materials such as steel,cement and plastic,which are also the four major building materials,wood resources have received more and more attention from scholars as the only renewable biomass material.The lattice sandwich structure not only have the advantages of high specific strength and stiffness,but also have the potential for multiple functions such as sound insulation,heat insulation,and earthquake resistance.Therefore,they have received extensive attention from scholars at home and abroad in recent years.In this thesis,we prepared a wood-based triangular prism lattice sandwich structure using plywood as the panel and birch round bar tenons as the core by the insertion-gluing method.The compression,short beam shear,and lateral compression properties of wood-based triangular prism lattice structures under multivariable conditions were analyzed through parameter design of different core diameters,unit specifications,drilling depths,and core lengths.A theoretical prediction model for triangular prism lattice sandwich structures was established.Finally,through theoretical prediction models and experimental results,the failure modes and failure mechanisms of triangular prism lattice sandwich structures under compression,short beam shear,and lateral compression loads are obtained,and the combination of triangular prism lattice sandwich structures with the best mechanical properties is found.This paper firstly describes the background of the research,and then reviews the current status of domestic and international research on the dot matrix structure of metallic,composite and biomass materials,from which the key problems to be solved in this topic are extracted.Regarding the study of the compressive properties of wood-based triangular prism lattice sandwich structure,the experimental raw materials,the configuration of wood-based triangular prism lattice sandwich structure and the fabrication process of the insertion-gluing method are firstly introduced and illustrated with diagrams.At the same time,the relevant knowledge of material mechanics is applied to derive the intrinsic structure relationship of the elastic phase of the structure under compressive load.Comparative experiments are set up according to different factors such as core diameter,drilling depth and core length,and the failure mode and compressive performance of the triangular prism lattice sandwich structure are analyzed based on the load-displacement curve and experimental phenomena of the compression experiments.The experimental results show that the out-of-plane compression damage mode of the woodbased triangular prism lattice sandwich structure is mainly shear damage of the core.The experimental values of compression modulus are smaller than the theoretical values.Within the designed parameters,the larger the core diameter,the deeper the drilling depth and the smaller the core length,the better the compressive performance of the wood-based triangular prism lattice sandwich structure.A three-point bending loading method is mainly used to study the short beam shear performance of wood-based triangular prism lattice sandwich structure under different unit specifications,drilling depths and core lengths,and parameters such as equivalent shear modulus and deflection response of single cell cores under different loading conditions are deduced using homogenization theory.The failure modes and short beam shear performance of the dot matrix core structure were analyzed by load-displacement curves and experimental phenomena.The experimental results show that the short beam shear damage mode of the wood-based triangular prism lattice sandwich structure is mainly the separation of the core from the panel and the panel crush damage,accompanied by the flexural and shear damage of the core.The experimental values of deflection response are larger than the theoretical values.Within the range of design parameters,the smaller the unit specification,the deeper the drilling depth,and the smaller the core length,the better the short beam shear performance and energy absorption performance of the wood-based triangular prism lattice sandwich structure.In order to investigate the lateral compression performance of wood-based triangular prism lattice structures,the in-plane compression performance under multivariate conditions was analyzed through parameter design of different core diameters,unit specifications,drilling depths,and core lengths.At the same time,the in plane compression test and theoretical prediction are combined to analyze and compare different failure types and multiple in plane compression parameters of the structure.The experimental results show that the main failure modes of wood-based triangular prism lattice structures under lateral compression are core and panel separation,panel collapse failure,panel delamination,and shear type macroscopic buckling failure.Panel failure often occurs near the mid span of the structure.The strength of the panel is a key factor determining the lateral compressive strength.Within the range of design parameters,the larger the core diameter,the larger the unit specification,and the longer the core length,the greater the lateral pressure bearing capacity of the wood-based triangular prism lattice sandwich structure.When the drilling depth is 10 mm,the lateral pressure bearing capacity and energy absorption of the structure are the largest.Compared with the traditional wood-based lattice sandwich structure with straight columns and inclined columns,the wood-based triangular prism lattice sandwich structure not only has the characteristics of light weight and high strength,but also has obvious shear and bending advantages.Because the core layer of triangular prism lattice sandwich structure has a large space connected with each other,it can be used as a multifunctional structure.In the future building structure field,the wood-based triangular prism lattice sandwich structure has great application prospects.