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An empirical 3-D model was developed to evaluate the effect of ambient environment on the mechanical properties and degradation behavior of bamboo-bundle laminated veneer lumber (BLVL) fabricated with different levels of PF/PVAc resin. This model can describe the relationship between the modulus of elasticity (MOE), water absorption ratio, and aging temperature. Five levels of PF/PVAc weight ratio (2:1, 4:1, 6:1, 8:1 and 10:1) and three treatment conditions (18, 63, and 100 °C) were examined in this experiment. Computed tomography (CT) scanning technology was employed to observe the morphology of damage degree as well as explore the mechanism of degradation behavior of BLVL. The results indicated that the 3-D model used for tracking and monitoring the variance of MOE provided good predictors. The higher the water impregnation temperature the larger the water absorption ratio and the higher the MOE degradation were. The aging temperature had a significant effect on the mechanical properties and degradation behavior of BLVL. A linear relationship between modulus of rupture (MOR) degradation and aging temperature was observed. The degradation rate of MOE and MOR increased as the temperature increased. The aging degree tested by CT along with damage of inner board showed the PF/PVAc ratio had a significant influence on the mechanical degradation of treated BLVL when the PF/PVAc ratio was below 6:1. Localized yielding, micro-cracks developing between interfaces, PVAc resin softening along with delamination, and debonding were the main failure models for the BLVL by hygrothermal aging treatment.

Understanding the effect of moisture absorption on the mechanical properties of fibers at cellular level is key important to the application of natural fibers in reinforcement composites. This study focused on the variation of the modulus of elasticity (MOE) of several representative individual cellulosic fibers (bamboo, Chinese fir, ramie and Kevlar) under different relative humidity condition (RH: 40 %, 70 %, 90 %), dedicating for the screening of appropriate candidates of fibers used in outdoors. A special custom-designed microtester (SF-I) with the micro humidity control box was devised in order to observe stress-strain behavior of fibers under different humidity condition. Among the fibers investigated, ramie fiber presented the most sensitive to the humidity, Chinese fir and bamboo fiber was followed, and Kevlar fiber showed the bluntest to moisture variation since it belonged to artificial fiber. Compared with the fibers tested at RH of 40 %, the MOE of Bamboo, Chinese fir, Ramie fibers increased at RH 70 %, and decreased at RH 90 %, respectively. The optimal tensile properties were observed for the bamboo fiber among tested single plant fibers, with a MOE value of 26.3-30.7 GPa, and RH of 70-80 % was deduced for obtaining the highest value of MOE under various humidity testing condition.

The occurrence of an interactive effect between warp and weft of woven fabrics under practical working conditions is an important concern for researchers. A novel 3D loading device has therefore been developed to elucidate information on materials subjected to loadings in multiple dimensions. This paper investigated the interactive effects between warp and weft in biaxial tension. Strain fields were characterized by digital speckle correlation method and Poisson’s ratio was calculated at 0° in the warp direction. The effects of different cutting angles and loading threshold values at 0° on the interactive effect were also evaluated. An interactive effect between warp and weft existed, and the influence of load at weft to warp was larger than warp to weft. Weft produced larger strain fields in both directions. As the load in the warp direction linearly increased, force values nonlinearly increased while load ratio decreased. Poisson’s ratio, however, was practically unchanged. Loading mean value curves at ...

Mechanical properties of woven ramie fabric under 3D loadings are fundamental to optimizing the design of woven composites that are frequently subjected to complex stress states. This work proposes a novel 3D test analysis system for evaluating woven natural-fiber fabrics under multidimensional loads. The effects of different loading directions, uniaxial (X direction), biaxial (X and Y), bursting (Z direction), and 3D loading (X, Y, and Z) on the breaking strength of the woven ramie (Boehmeria nivea) fabric were compared. Weft breaking strength was lower than that of warp under uniaxial tension. Variability in warp and weft increased in biaxial tension. Bursting strength was significantly affected by the type of loading head used, with an R20 spherical head producing the highest strength values. Warp and weft were positively correlated under biaxial tension, r = 0.58. The synergistic effect of bursting strength accounted for 12.5% of the total correlation under 3D loadings.

As a new textile fiber produced from Neosinocalamus affinis, the structures of the bamboo fiber were studied thoroughly in this research. Using Fourier-transform infrared (FTIR) (using a Micro-FTIR Spectrometer), X-ray diffraction (XRD), nuclear magnetic resonance (NMR) spectroscopy and scanning electron microscopy (SEM), we investigate the chemical composition, crystalline structure, molecular and morphology structure, respectively. Results show that the chemical composition of bamboo fiber is the same as all bast fibers, that is, cellulose constitutes the majority and lignin needs to be reduced further for textile applications. The bamboo fiber belongs to cellulose I crystalline structure as flax, cotton and ramie, while has a small molecular mass and a low degree of polymerization. The cross section of the single bamboo fiber is round with small lumen. It can be predicted that bamboo fiber has high breaking strength, but low elongation and has good water absorption properties. The structural characteristics of the bamboo fiber are different from those of other textile plant fibers.