摘要：
Large-scale parallel bamboo strand lumber (PBSL) structural elements are often subjected to local compression especially in beam-to-column connections as well as in beam-to-beam connections. The current paper presents an experimental investigation on the local compression behaviour of PBSL. 20 specimens were collected from different parts of a PBSL block under radial and tangential compression loading. Load-displacement curves of all specimens were recorded and observed failure patterns were carefully investigated to understand underlying mechanics. Tangentially loaded specimens predominantly failed due to debonding of fibres triggered by deformations perpendicular to the grain. On the other hand, radially loaded specimens showed a combined failure caused by debonding in perpendicular to the grain direction as well as tensile failure of bamboo fibres in the longitudinal direction. Key design parameters such as elastic modulus, stiffness, ultimate strength and Poisson's ratio for all specimens were computed and compared against end vs middle specimens as well as radial vs tangential specimens. Radially loaded specimens showed higher load carrying capacity due to better bonding, whilst the specimens collected from the middle part of the PBSL block were relatively more ductile than the others. Analytical models for load-displacement repose as well as for stress-strain behaviour were proposed for the considered specimens. Ramberg-Osgood based stress-strain model showed good agreement with test results. (C) 2020 Elsevier Ltd. All rights reserved.
作者机构：
[孙振宇; 张源; 左迎峰; 吴义强; 王张恒; 吕建雄] College of Materials Science and Engineering, Central South University of Forestry and Technology, Changsha;410004, China;Research Institute of Wood Industry, Chinese Academy of Forest, Beijing;100091, China;[孙振宇; 张源; 左迎峰; 吴义强; 王张恒] 410004, China
作者机构：
[李萍; 张源; 左迎峰; 吴义强] College of Materials Science and Engineering, Central South University of Forestry and Technology, Changsha, 410004, China;[Lyu J.] Research Institute of Wood Industry, Chinese Academy of Forestry, Beijing, 100091, China;[王向军] Tianying (Guangdong) Wood Industry Technology Limited Company, Guangdong, Jiangmen, 529700, China
作者机构：
[周亚; 李萍; 张源; 袁光明; 吴义强; 左迎峰] College of Materials Science and Engineering, Central South University of Forestry and Technology, Changsha;410004, China;[王向军] Tianying (Guangdong) Wood Industry Technology Limited Company, Jiangmen;529700, China;[周亚; 李萍; 张源; 袁光明; 吴义强; 左迎峰] 410004, China
通讯机构：
College of Materials Science and Engineering, Central South University of Forestry and Technology, Changsha, China
摘要：
To improve the hydrophobicity and thermoplastic processability of starch, lactic acid esterified starch (LA-e-starch) was prepared by in-situ solid phase esterification with corn starch as the raw material and LA as the esterifying agent. Fourier transform infrared spectroscopy confirmed that the esterification reaction was successful. The optimal esterification efficiency of LA-e-starch was obtained when the LA proportion was 20% by mass, catalyst ratio at 3%, reaction temperature 80 degrees C and reaction time 2.5 h. LA-e-starch was characterized by scanning electron microscopy (SEM), contact angle (CA) analysis, X-ray diffractometry (XRD), differential scanning calorimetry (DSC), and thermogravimetric analysis (TGA) as well as its water absorption rate evaluated. Results showed that in-situ solid phase esterification mainly occurred on starch granule surfaces and did not destroy the starch granularity. LA-e-starch surfaces were covered with a layer of polylactic acid resin, which caused starch granules to stick together. The initial contact angle of LA-e-starch was clearly larger than that of native starch and the water absorption rate lower than native starch in a 168 h test time, which showed that esterification effectively improved the hydrophobicity of starch. This esterification destroyed the crystalline structure of starch to some extent, resulting in a crystallinity reduction to 25.16%. In addition, the gelatinization temperature and enthalpy were lower than those of native starch. XRD and DSC analyses indicated that esterification modification increased starch thermoplasticity. Also, LA-e-starch exhibited better thermal stability than native starch, from which it was inferred that this application of esterification could improve the thermoplastic processability of starch modify the interfacial compatibility between starch and polymer resins.
摘要：
To improve the properties of polylactic acid-grafted-bamboo fiber/polylactic add (PLA-g-BF/PLA) composite, a compatible interface was constructed by adding nano-silica (nano-SiO2). The results showed that, with increased nano-SiO2 mass ratio, the composites' mechanical strength and water resistance were significantly improved. The composite with a 1.5% nano-SiO2 mass ratio exhibited the best mechanical properties and water resistance. Strain scanning results showed that the strain value at which the storage module (G') of the composite began to decrease was the largest with 1.5% nano-SiO2 and the G' and complex viscosity (eta*) of the composite also reached the best state at this point. The interfadal compatibility between PLA-g-BF and PLA was also confirmed to be the best at this mass ratio. SEM and TEM analyses indicated that, when the mass ratio of nano-SiO2 was 1.5%, nanoparticles were uniformly dispersed in the composite and PIA-g-BF and PLA in a state of integration. The addition of nano-SiO2 was beneficial for the crystallization and nucleation of PLA, and composite crystallinity with 1.5% nano-SiO2 reached the maximum value. With increased interfacial compatibility and crystallinity of the composite, the thermal stability was also best when the mass ratio of nano-SiO2 was 1.5%. (C) 2020 Elsevier B.V. All rights reserved.
作者机构：
[张源; 袁光明; 左迎峰; 吴义强] College of Materials Science and Engineering, Central South University of Forestry and Technology, Changsha, 410004, China;College of Art and Design, Xiangnan University, Chenzhou, 423000, China;Research Institute of Wood Industry, Chinese Academy of Forestry, Beijing, 100091, China;[李萍] College of Materials Science and Engineering, Central South University of Forestry and Technology, Changsha, 410004, China, College of Art and Design, Xiangnan University, Chenzhou, 423000, China;[Lü J.] College of Materials Science and Engineering, Central South University of Forestry and Technology, Changsha, 410004, China, Research Institute of Wood Industry, Chinese Academy of Forestry, Beijing, 100091, China
通讯机构：
[Zuo, Y.] C;College of Materials Science and Engineering, China
作者机构：
[左迎峰; 屠茹茹; 李萍; 周亚; 吴义强] College of Materials Science and Engineering, Central South University of Forestry and Technology, Changsha;410004, China;[左迎峰; 屠茹茹; 李萍; 周亚; 吴义强] 410004, China
通讯机构：
[Wu, Y.] C;College of Materials Science and Engineering, China
摘要：
Three kinds of hydrophobic groups grafted starches of maleic anhydride grafted starch (MAH-g-starch), lactic acid grafted starch (LA-g-starch), and methyl acrylate grafted starch (MA-g-starch) were prepared by in situ solid phase polymerization. The results of Fourier transform infrared spectroscopy (FT-IR) and X-ray photoelectron spectroscopy (XPS) confirmed successful grafting. The grafting ratios of MAH-g-starch, LA-g-starch, and MA-g-starch were 6.50%, 12.45%, and 0.57%, respectively. Influenced by the grafting ratio, LA-g-starch had the best relative hydrophobicity and the largest molecular weight, and those for MA-g-starch were the worst. The surfaces of grafted starches were covered with graft polymer, with obvious surface roughness and bond degree of MAH-g-starch and LA-g-starch. The crystalline structure of grafted starches showed some damage, with LA-g-starch exhibiting the greatest decrease in crystallinity, and less of a change for MA-g-starch. Overall, the grafting reaction improved thermoplasticity, with LA-g-starch the most improved, followed by MAH-g-starch, and then MA-g-starch.
摘要：
The in-situ reactive interfacial compatibilization and properties of polylactic acid-g-bamboo fiber (PLA-g-BF)/polylactic acid (PIA) composites, produced by blending with a three-component plasticizer, glycerol/formamide/tributyl citrate, were investigated. The PLA-g-BF/PLA composites were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), differential scanning calorimeter (DSC), thermal gravimetric analyzer (TGA) and rotational rheometer, and the bending, tensile, and water resistance properties were also tested. The bending strength and elongation at break of PLA-g-BF/PLA composite reached 35.6 MPa and 5.59%, which increased by 19.3% and 30.1% relative to the ungrafted composites. The initial contact angle of the PLA-g-BF/PLA composite was 74.3 degrees, which was larger than that of the ungrafted composite (41.2 degrees), and the water absorption ratio reached 4.3% after 24 h, which was less than the unmodified material (6.1%). SEM results showed that PIA matrix showed smooth surfaces and the interfacial adhesion between modified BF and matrix PLA was greatly improved after grafting modification. The crystal structure results proved that the grafting treatment of BF strengthened the interfacial interactions between the filler BF and matrix PLA, and reduced the mobility of PLA molecular chain. The rotational rheometer illustrated that the initial storage modulus of PLA-g-BF/PLA composites was the largest and decreased slowly, which improved the processing properties of composites. (C) 2019 Elsevier B.V. All rights reserved.
作者机构：
[李萍; 吴义强; 刘文杰; 左迎峰; 屠茹茹] College of Materials Science and Engineering, Central South University of Forestry and Technology, Changsha;410004, China;[吕建雄] Research Institute of Wood Industry, Chinese Academy of Forest, Beijing;100091, China;[李萍; 吴义强; 刘文杰; 左迎峰; 屠茹茹] 410004, China
通讯机构：
[Zuo, Y.] C;College of Materials Science and Engineering, China
作者机构：
[李萍; 左迎峰; 吴义强; 赵星; 王健] College of Material Science & Engineering, Central South University of Forestry & Technology, Changsha;410004, China;College of Art & Design, Xiangnan University, Chenzhou;423000, China;[李萍] 410004, China<&wdkj&>College of Art & Design, Xiangnan University, Chenzhou
