The Interspecific Difference Of Bamboo Mechanical Properties And Its Influencing Factors

Basic material data are the basis of bamboo utilization.Obtaining comprehensive basic material data can meet the demand for bamboo in different application fields.Eleven monopodial and sympodial bamboo species,which had good economic value and representativeness in Fujian Province.including Bambusa pervariabilis,Bambusa chungii,Neosinocalamus affinis,Dendrocalamopisis vario-striata,Phyllostachys heteroclada,Bambusa eutuldoides var.viridi-vittata,Dendrocalamus latiflorus,Bambusa albo-lingata,Dendrocalamopisis oldhami,Bambusa longispiculata,Phyllostachys edulis were studied.The differences of macro-mechanical properties,vascular bundle mechanical properties,density,fiber tissue ratio,radial gradient distribution of fibers,microfibril angle,culm wall thickness,inner diameter and chemical composition were systematically compared.The main influencing factors of mechanical properties of bamboo were compardd and analyzed.The aim was to provide scientific basis for rapid selection and utilization of different bamboo species.The main results are as follows:(1)The physical and mechanical properties of eleven bamboo species were significantly different from each other,The tensile strength and modulus ranged from 144.03 to 317.25 MPa,and form 12.42 to 22.46 Gpa,respectively.The bending strength was from 135.32 to 238.96MPa,and modulus of elasticity was between 10.39 and 17.77 GPa.The compressive strength ranged from 68.01 to 127.86 MPa,and compressive modulus was between 5.21 and 11.85GPa.Shear strength ranged from 10.34 to 18.66 MPa.The density of seven bamboo species with better mechanical properties was equal or higher than Phyllostachys heterocycle bamboo.The mechanical properties of the seven bamboo species(Bambusa pervariabilis,Bambusa chungii,Neosinocalamus affinis,(Phyllostachys heteroclada,Bambusa eutuldoides var.viridi-vittata,Bambusa albo-lingata,Bambusa longispiculata)were better than those of Phyllostachys edulis,the comprehensive mechanical properties of Bambusa eutuldoides var.viridi-vittata bamboo were the best(excpet the bending strength),and the mechanical properties of two year Dendrocalamopisis oldhami bamboo and the Dendrocalamus latiflorus bamboo were the worst among the bamboo species.(2)The chemical compositions of the eleven bamboo species were also significantly different.The content of phenyl alcohol extracts ranged from 2.32%to 6.28%,holocellulose from 69.59%to 82.29%,?-cellulose from 43.11%to 60.94%,hemicellulose from 15.58%to32.38%,acid-insoluble lignin from 20.41%to 24.08%,ash from 0.47%to 2.31%.The basic density ranged from 0.43 g/cm~3to 0.77g/cm~3,The average fiber tissue ratio of the eleven bamboo species was from 0.29 to 0.50,and the fibre tissue ratio of seven bamboo species with better mechanical properties was also higher than that of Phyllostachys edulis.(3)An image processing method was proposed to characterize the radial gradient of bamboo fiber volume ratio.It was found that the radial gradient distribution pattern of bamboo fiber tissue ratio could be divided into three types:convex,concave and approximate S-type.The probability of S-type distribution pattern was significantly higher than the other two.(4)The tensile strength of vascular bundles from the outer layer of eleven bamboo species ranged from 381.20 to 880.06 MPa,from 258.66 to 703.14 MPa from the middle area,and192.18 to 685.15 MPa from the inner later of bamboo.The tensile modulus of vascular bundles from the eleven bamboo species ranged from 26.12 to 94.88 GPa,17.78 to 63.68 GPa and15.15 to 41.28 GPa,respectivley for the vascular bundles from outer layer,middle area and inner layer.Among the eleven bamboo species,the tensile properties of the vascular bundles of Bambusa eutuldoides var.viridi-vittata were the best,while those of Phyllostachys edulis were the worst.The reduced radial variation of the mechanical properties of the vascular bundles from the outer layer to the inner layer of bamoo was obvious(5)Density was the most important determinant for inter-species difference in mechanical properties of bamboo,followed by fiber tissue ratio,There was also a good correlations between wall thickness,ash content and mechanical properties of bamboo,which can be explainde by the obvious correlation anmong wall thickness,ash content and the density of bamboo.There was a positive correlation between the mechanical properties of bamboo and the content of holocellulose and hemicellulose.Microfibril Angle and lignin had no significant effect on mechanical properties of the eleven bamboo species.In addition,the principal component regression model showed that at least 80%of the variation of bamboo mechanical properties was caused by the following eight indicators,including density,fiber tissue ratio,bamboo wall thickness,as well as the content of holocellulose,hemicellulose and ash.