Experimental Research On Non-destructive Test And Fungal Decay Resistance Of Bamboo Scrimber

Bamboo scrimber is a kind of engineered bamboo processed by thermal treatment,drying,impregnaing,drying,assembling,hot-pressing(cold-pressing)and curing,which is similar to the fabrication process of timber scrimber.It has the characteristics of high utilization rate of bamboo,excellent mechanical properties,meticulous uniformity and beautiful texture.Firstly,the mechanical properties of three kinds of bamboo scrimber(cold-pressing bamboo scrimber,hot-pressing bamboo scrimber and bamboo-based fiber composites)were studied and compared.And then the feasibility of non-destructive testing for mechanical properties of bamboo scrimber also was explored.Secondly,the fungal decay resistance tests of hot-pressing were conducted.The effects of brown-rot fungi and white-rot fungi on mechanical properties of bamboo scrimber were analyzed,and the SEM was used to explore the decay mechanism.Finally,the decay hazards of China was completed according to Scheffer index and compared with " Standard of Climatic Regionalization for Architecture ".The main conclusions of this thesis are as follows:(1)Althrough there are obvious differences among the three kinds of bamboo scrimber,but the mechanical properties of hot-pressing bamboo scrimber are uniform and stable.Based on the experimental data,the relationship between density and flexural strength,flexural modulus and compressive strength is established,and the relationship between density and compressive strength is the closest.The relationship between flexural elastic modulus and flexural strength,compressive strength and tensile strength is established on the basis of considering that the strength values of different mechanical strength properties have the same cumulative probability are one-to-one correspondence.(2)It is proved that the indirect ultrasonic wave velocity can be used to evaluate the mechanical properties of bamboo scimber.The reasonable velocity range and average velocity of different bamboo scimber are determined.The critical velocity of three bamboo scimber defect detection is given by mathematical statistics method.The relationship between dynamic elastic modulus and flexural elastic modulus,flexural strength and compressive strength is established.And the flexural modulus and compressive strength of three kinds of bamboo scrimber are predicted by dynamic modulus of elasticity and density,which is more accurate than that predicted by dynamic modulus of elasticity or density alone.(3)The accelerated decay tests in the laboratory on hot-pressing bamboo scimber show that for both white-rot fungi or brown-rot fungi,visual evaluation of bamboo scimber after decay for 12 weeks show firstgrade decay resistance;weight loss evaluation show grade ? decay resistance;but mechanical properties analysis show that white-rot fungi had greater impact on mechanical properties of bamboo scimber;SEM showed that neither brown-rot fungi nor white-rot fungi could infect bamboo scimber inside 2 mm below.The study on the decay mechanism show that even the bamboo scimber could achieve the conditions of fungal colonization and reproduction,but compared with the raw bamboo,the mycelial infection pathway are less,the water entry pathway are less,and the phenolic resin with bacteriostatic properties is also contained,which ultimately made the bamboo scimber resistant to decay.(4)The grade division of decay hazards completed by Sheffer index is in good agreement with the Standard of Climatic Regionalization for Architecture.Grade A corresponds mainly to Grade VI and Grade VII of the building zoning,Grade B corresponds mainly to Grade I and II of the building zoning,and Grade C corresponds mainly to Grade III and IV of the building zoning.——The relationship between degree of day,relative humidity,percentage of sunshine and Scheffer index can provide basis data for future design.