Study On Quasi-static And Dynamic Mechanical Properties And Failure Mechanism Of Bamboo Scrimber

Bamboo scrimber is a new type of bamboo fiber reinforced composite material,which is basically composed of bamboo fiber bundle,matrix tissue and resin colloid.It is made of raw bamboo through the processes of truncation,splitting,peeling,thawing,drying,carbonization,dipping,paving and hot pressing.Compared with the original bamboo,bamboo scrimber has more uniform density,regular shape and better mechanical properties.At present,it is widely used in indoor and outdoor floors,decoration,landscape guardrails,furniture and other fields.It also has broad application prospects in the outdoor field,however,there is a lack of systematic research on quasi-static mechanical properties,dynamic mechanical properties and impact mechanical properties at the structural level,therefore it is necessary to explore and summarize these properties.In this thesis,the density and moisture content of commercial bamboo scrimber products were measured,the quasi-static mechanical properties and dynamic mechanical properties of bamboo scrimber at the material level were studied.The impact mechanical properties at the component level,relevant failure modes,failure mechanism and energy absorption were investigated.The following conclusions were obtained,（1）Bamboo scrimber is a fiber-reinforced composite material which is orthotropic,its tensile and compressive properties along the grain direction are much greater than the other two directions,while the compressive properties of the other two directions are relatively close.The shear resistance is the best in the direction perpendicular to grain,the bending resistance is excellent.The phenomenological constitutive model of the tensile and compression of bamboo scrimber is summarized,and the relevant mechanical properties of tension,compression,shear and bending are obtained.（2）Elastic deformation occurs in the tensile process of the bamboo scrimber,and the failure type is brittle fracture;while the compression process can be divided into three stages of elastic deformation,nonlinear strengthening and linear strengthening,and the failure type is ductile failure.The causes of all failure types at the mesoscopic level can be divided into those caused by fiber breakage,matrix failure,and fiber/matrix interface debonding.（3）Bamboo scrimber shows obvious strain rate effect under dynamic loading.In the compression and tensile tests under different strain rates in different directions,the ultimate strength increases with the increase of strain rate,and the corresponding specific strain energy also increases with increasing strain rate.Among them,the micro mechanism of strain rate effect of dynamic compression can be explained as localization,micro inertia and densification.（4）The bamboo scrimber plate components have different impact resistance performance when impacted by different shapes of hammer,among which the impact toughness of the cylindrical hammer is the largest.With the continuous increase of the impact energy,the peak load,peak displacement and impact toughness are increasing.The impact damage type shows that the damage degree of the incident surface is greater than that of the exit surface.It can be explained as fiber breaking,matrix shearing and interface debonding in the mesoscopic level.The energy absorption mechanism is divided into deformation energy absorption and destruction energy absorption.