Issue 35

T. Haiyan, Frattura ed Integrità Strutturale, 35 (2016) 472-480; DOI: 10.3221/IGF-ESIS.35.53 479 Figure 6 : Correlation between elastic module of bamboo and volume fraction of fiber. Both V f and V b were defined as 0. Then we obtained the tensile strength of bamboo fiber 588.732MPa f   , tensile strength of ground tissue 19.042 b MPa   and elastic modulus E b =0.2219GPa based on Eq. (1). Thus we consider bamboo fiber is the main component bearing load and its strength is larger than general steel materials. C ONCLUSIONS nder the effect of load, different mechanism associated with internal damage and crack of materials can induce different degrees of energy release, leading to abundant acoustic emission signals. Applying acoustic emission technology can help identify the emergence and extension of different types of damage produced on wood in the process of loading. Test results indicate the following three points. Firstly, defect-free samples have slowly developed acoustic emission events in the initial stage of loading, and acoustic emission signals that emerge in that period are of low amplitude; a large number of high-amplitude acoustic amplitude signals emerge when loading reaches the peck value or crack appears. Secondly, monitoring the damage of crack process of defective wood under three-point bending loading with acoustic emission can effectively identify initial stage of crack and extension stage. Thirdly, characteristics of acoustic emission signals are associated with damage mode of wood; acoustic emission characteristics regarding facture on cell wall is high-amplitude, high-energy and long-lasting, while acoustic emission corresponding to cell wall interface damage and spalling damage as well as cell bending and collapse damage is low-amplitude, low-energy and lasts for short time. We tested and analyzed mechanical performance of bamboo samples cut from bamboo wall along radial direction and bamboo fiber bundle isolated from bamboo materials with rule of mixture and shearing-lag theory. We found strength and elastic modulus of bamboo cut from bamboo wall along radical direction was positively correlated with volume fraction of bamboo fiber. Fibre bundle of three-year moso-bamboo was detected to have 588.72 MPa tensile strength and 40.35Gpa elastic modulus and tensile strength and elastic modulus of ground tissue were 19.42 MPa and 0.222 GPa. Tensile strength and elastic modulus of single bamboo fibre bundle were detected to be 482.18 MPa and 33.85 GPa. Thus we draw conclusions that, ground tissue is capable of transferring loading and dispersing stress loaded by fibre bundle evenly and strength of bamboo fiber gathering in ground tissue is higher than isolated bamboo fibre bundle. R EFERENCES [1] Duggan, T.V., Fatigue and fracture mechanics, Physics in Technology, 14(3) (1983) 126-132. [2] He, W., Nakao, T., Yoshinobu, M., Treatment of fast-growing poplar with monomers using in situ polymerization, Part I: Dimensional stability and resistance to biodegradation, Forest Prod J, 61(2) (2011) 113-120. [3] Shao, Z., Jiang, Z., The particularity of application of principles of linear-elastic fracture mechanics to wood and fracture parallel to grain, Scient Silv Sinic, 38(6) (2002) 110-115. U