Investigation On Modulus Of Elasticity Of Lamination And Glued Laminated Timber

The modulus of elasticity of wood is an important index of its mechanical properties and has close correlation with other mechanical properties.At present,scholars at home and abroad have been trying to use nondestructive testing of modulus of elasticity of wood,and achieved good results.However,there are still the following problems:1)Influenced by initial defects,ambient temperature,water content,etc.,it is usually difficult to accurately characterize the variation degree of mechanical properties of wood using only one overall elastic modulus value,and the elastic modulus value obtained by continuous bending detection is not accurate enough;2)In the studies of finger-jointed woods,the same properties of the parts of wood being finger-jointed are considered,but the differences in wood properties caused by the variability of wood are not considered;3)The modulus of elasticity and the corresponding coefficient of variation of glued laminated timber can reflect the objective indexes of its mechanical properties.However,there is no unified method to adjust the data measured by different test methods in different countries to a unified standard.This paper takes lamination and GLT as the research object,and carries out finite element simulation analysis,experimental research and theoretical analysis methods for them respectively.Main research contents and conclusions are as follows:(1)Summarize the influence of moisture content,density,temperature,wood junction,twill,specimen size,test method and other factors on the modulus of elasticity of wood in Chinese and foreign literatures.The influence of loading mode and the ratio of span to height on the modulus of elasticity was analyzed by finite element simulation method,and the correlation between the real elastic modulus and the measured flexural elastic modulus under different span to height ratio was determined.(2)A method for the reconstruction of the modulus of elasticity of the lamination was proposed.The modulus of elasticity of the lamination was expressed by the flexural modulus of the lamination with finite length,and the formula between the modulus of elasticity of the lamination and the sectional modulus of elasticity and the length coefficient was derived.(3)Based on the finite element software ABAQUS platform,the lamination were divided into two and three sections equally,and the formula of high correlation between the modulus of elasticity of lamination and the two and three sections equally was obtained.The correlation formula of modulus of elasticity between the laminates with different properties was obtained by finger grafting.(4)The elastic modulus test of 40 laminations was carried out to verify the conclusion of the finite element simulation analysis,and the spline curve and cumulative distribution curve of the elastic modulus of laminations were obtained.The representative value analysis of the curve data showed that the elastic modulus of wood planks was closer to the average value of the cumulative distribution curve.(5)The relationship between the modulus of elasticity of GLT with equal thickness and the modulus of elasticity of each lamination was deduced.The correlation between the modulus of elasticity and the coefficient of variation between the same and different composite GLT and composite laminations was obtained.