热模压工艺参数对聚乳酸/竹纤维复合材料拉伸强度的影响

采用四元二次通用旋转组合设计试验方法,研究了聚乳酸与竹纤维混合比例(PLA/BF)、竹纤维粒径、热模压温度、热模压时间等4个因素对聚乳酸/竹纤维复合材料拉伸强度(TS)的影响,并采用差示扫描量热仪(DSC)对复合材料进行了热力学表征。结果表明,PLA/BF、热模压温度、热模压时间对复合材料的拉伸强度影响显著,热模压温度与热模压时间存在显著的交互效应。DSC分析显示,PLA/BF、竹纤维粒径、热模压温度/时间工艺参数影响材料中PLA的结晶度(Xm)。本试验条件下的聚乳酸/竹纤维复合材料热模压优化工艺参数为:PLA/BF为90/10,竹纤维过100目标准筛,热压温度160℃,热压时间25min,理论最大TS为66.40MPa。     

Atmospheric pressure glow discharge plasma polymerization for surface treatment on sized basalt fiber/polylactic acid composites

This study evaluates the effects of atmospheric pressure glow discharge plasma polymerization on basalt fiber to the properties of basalt fiber/polylactic acid composite. Plasma exposure time was the object of interest so the basalt fiber was exposed to the glow for 0.5, 1.5, 3, 4.5, and 6 min, respectively. Characterization was conducted on the plasma polymerized fibers by identifying the molecular bonds and surface morphology. Properties (mechanical and thermal) and water absorption behavior of the fabricated composites were tested. Plasma exposure time on BF affected mechanical properties of its BF/PLA composite, showing a decline in mechanical properties until the BF was plasma polymerized beyond 1.5 min. Optimum plasma polymerization on BF was for 4.5 min of plasma exposure time where the composite’s strength and modulus were 45% and 18% higher, respectively, compared to those of untreated one.     

玄武岩纤维含量对玄武岩纤维/聚乳酸-铝合金复合材料连接强度的影响

为了提高聚乳酸（PLA）与铝合金的连接强度,采用在PLA中添加玄武岩纤维（BF）获得BF/PLA复合材料的方式对PLA进行增强。利用转矩流变仪对干燥处理后的PLA及BF进行密炼,利用光纤激光器对铝合金表面进行毛化处理。采用平板硫化机对BF/PLA复合材料和处理后铝合金进行连接成型,测试其拉伸强度,对失效后断面进行分析。结果表明:随着BF质量分数的增加,BF/PLA-铝合金连接强度先增强后降低,BF质量分数的增加影响了BF/PLA复合材料的结晶成核。结合试验获得的结果,建立有限元分析模型进行数值模拟,结果显示所建立的模型能够准确还原BF/PLA-铝合金拉伸过程。      

Multi-scale hybrid biocomposite: Processing and mechanical characterization of bamboo fiber reinforced PLA with microfibrillated cellulose

In this research we develop novel hybrid biocomposites based upon a biodegradable poly(lactic acid) (PLA) matrix reinforced with microfibrillated cellulose (MFC) and bamboo fiber bundles. Due to the relative difference in scale between microfibrillated cellulose and bamboo, a hierarchy of reinforcement is created where bamboo fiber bundles are the primary load-carrying reinforcement and cellulose creates an interphase in the polymer matrix around the bamboo fiber that prevents sudden crack growth. The influence of MFC dispersion on the properties of the PLA matrix was investigated and substantial improvements in the strain energy until fracture observed. By adding just 1 wt% of MFC with a high degree of dispersion an increase in fracture energy of nearly 200% was obtained. In the hybrid bamboo/MFC/PLA composites there is also a dramatic change in the fracture morphology around the bamboo fiber bundles.     

竹纤维增强聚乳酸复合材料热老化性能

采用氢氧化钠和异氰酸酯处理的界面调控方法对竹纤维(BF)增强聚乳酸(PLA)复合材料界面进行调控,通过注射成型工艺制备BF/PLA复合材料。利用FTIR、XRD、凝胶渗透色谱及SEM等分析手段研究了BF/PLA复合材料热老化性能。研究发现: 热老化过程中PLA分子链中的C O不断水解,分子链的C—O断裂生成聚合度更低的小分子量的PLA,PLA结晶度减小,PLA与BF的接合界面被破坏,拉伸强度和冲击强度随老化时间的增加逐渐降低。BF/PLA复合材料在80℃热老化16天后拉伸强度和冲击强度分别降低了75%和77.6%,在100℃热老化32 h后拉伸强度和冲击强度分别降低了80.3%和83.4%。温度对BF/PLA复合材料老化影响显著,温度越高,老化速度越快。     

Development and characterization of a laminate composite material from polylactic acid (PLA) and woven bamboo fabric

This article presents the development and mechanical characterization of a composite material fabricated from both renewable resources and biodegradable materials: bamboo woven fabric as reinforcement and polylactic acid (PLA) as resin matrix. The laminate composites were produced using a film stacking method. The physical, thermal, and, mechanical properties of bamboo fabric, PLA matrix, and laminate composites were investigated. It is shown that the breaking force of the plain woven bamboo fabric in the weft direction was greater than in the warp direction. Further, the tensile, flexure, and, impact properties of PLA increased when weft direction bamboo fabric reinforcement is used. In addition, scanning electron microscopy examination of laminate composite showed good bonding between bamboo fiber and PLA resin. In summary, laminated composites based on polylactic acid and bamboo fabric display excellent energy absorption capability, which can be exploited for the development of engineering structural applications.     

Fabrication and characterization of fully biodegradable natural fiber-reinforced poly(lactic acid) composites

Polymer composites were fabricated with poly(lactic acid) (PLA) and cellulosic natural fibers combining the wet-laid fiber sheet forming method with the film stacking composite-making process. The natural fibers studied included hardwood high yield pulp, softwood high yield pulp, and bleached kraft softwood pulp fibers. Composite mechanical and thermal properties were characterized. The incorporation of pulp fibers significantly increased the composite storage moduli and elasticity, promoted the cold crystallization and recrystallization of PLA, and dramatically improved composite tensile moduli and strengths. The highest composite tensile strength achieved was 121 MPa, nearly one fold higher than that of the neat PLA. The overall fiber efficiency factors for composite tensile strengths derived from the micromechanics models were found to be much higher than that of conventional random short fiber-reinforced composites, suggesting the fiber–fiber bond also positively contributed to the composites’ strengths.     

Manufacture and characterisation of thermoplastic composites made from PLA/hemp co-wrapped hybrid yarn prepregs

PLA/hemp co-wrapped hybrid yarns were produced by wrapping PLA filaments around a core composed of a 400 twists/m and 25 tex hemp yarn (Cannabis sativa L) and 18 tex PLA filaments. The hemp content varied between 10 and 45 mass%, and the PLA wrapping density around the core was 150 and 250 turns/m. Composites were fabricated by compression moulding of 0/90 bidirectional prepregs, and characterised regarding porosity, mechanical strength and thermal properties by dynamic mechanical thermal analysis (DMTA) and differential scanning calorimetry (DSC). Mechanical tests showed that the tensile and flexural strengths of the composites markedly increased with the fibre content, reaching 59.3 and 124.2 MPa when reinforced with 45 mass% fibre, which is approximately 2 and 3.3 times higher compared to neat PLA. Impact strength of the composites decreased initially up to 10 mass% fibre; while higher fibre loading (up to 45 mass%) caused an increase in impact strength up to 26.3 kJ/m², an improvement of about 2 times higher compared to neat PLA. The composites made from the hybrid yarn with a wrapping density of 250 turns/m showed improvements in mechanical properties, due to the lower porosity. The fractured surfaces were investigated by scanning electron microscopy to study the fibre/matrix interface.     

蔗渣纤维表面处理方法对蔗渣纤维/聚乳酸复合材料力学性能的影响

采用了硅烷偶联剂结合碱溶液处理的方法对蔗渣纤维(BF)进行了表面改性, 研究了不同表面处理方法对蔗渣纤维/聚乳酸(PLA)复合材料力学性能的影响, 用SEM对BF处理前后的形貌及复合材料的冲击断面进行了观察。结果表明: 经表面改性的BF都不同程度地改善了BF与PLA基体之间的界面相容性, 其中碱处理后再经偶联剂处理的方法效果最佳, 在40%(质量分数)蔗渣纤维的高填充量下, 复合材料的拉伸强度和冲击强度分别为纯PLA的85.42%和59.74%, 较好地保持了基体PLA的力学强度; 碱处理使BF表面变粗糙、 长径比增大、 比表面积增加, 与PLA的界面粘结加强, 从而有效地提高了BF/PLA复合材料的力学性能。     

竹纤维组合形态对竹纤维/聚丙烯复合材料性能的影响

以聚丙烯（PP）为基体,单根竹纤维（SBF）和竹纤维束（BFS）两种形态竹纤维为增强体,采用无纺气流铺装-模压工艺制备了SBF-BFS/PP复合材料。通过力学试验机、SEM、TGA、DSC等对SBF-BFS/PP复合材料的力学性能、微观形貌、热性能等进行表征,研究竹纤维形态配比变化对SBF-BFS/PP复合材料综合性能的影响。结果表明,在纤维总含量不变情况下,SBF在两种形态竹纤维中的含量逐步增加时,SBF-BFS/PP复合材料冲击强度和弹性模量逐步增加; SBF在两种形态竹纤维中质量分数为90wt%时,SBF-BFS/PP复合材料冲击强度和弹性模量比SBF质量分数为10wt%时分别提高了26.46%和38.39%; SEM结果表明,竹纤维与PP基体存在较差界面相容性,竹纤维出现断裂和拔出等现象;热失重结果表明,随着SBF含量的增加,SBF-BFS/PP复合材料的耐热性能并没有明显变化。此外,对SBF-BFS/PP复合材料的耐水性能测试结果表明,由于SBF比表面积大,随SBF含量的增加,SBF-BFS/PP复合材料中易吸水组分增加,从而导致其耐水性能下降。      

单向竹原纤维表面改性对其增强不饱和聚酯树脂复合材料性能的影响

采用碱处理、碱-偶联剂联合处理对竹原纤维进行表面改性,通过缝合-模压工艺制备了单向连续竹原纤维/不饱和聚酯树脂(BF/UP)复合材料。研究了不同表面改性方法对BF/UP复合材料静态、动态力学性能、吸水性能等的影响,并用SEM、红外光谱等技术研究了改性处理后纤维的表面及复合材料界面结合情况。结果表明:经过不同表面处理后BF/UP复合材料的性能均有所改善。当采用5wt%碱-3wt%偶联剂联合处理时,BF/UP复合材料综合性能最优,其拉伸强度、弯曲强度、弯曲模量、剪切强度较未处理的分别提高了34.29%、15.95%、11.26%、29.39%;复合材料存储模量(33℃)较未处理的提高了63.80%,损耗因子有所降低;BF/UP复合材料24h、720h吸水率较未处理的分别减小了55.35%、27.32%。SEM和红外光谱结果表明,改性处理后竹原纤维表面杂质减少,附着了一层偶联剂膜,BF/UP复合材料中纤维与树脂之间的界面结合更好。     

粘胶纤维与Lyocell纤维增强聚乳酸复合材料的性能比较

以聚乳酸(PLA)为基体,分别采用粘胶纤维与Lyocell纤维这2种典型的再生纤维素纤维为增强纤维,通过熔融共混和注塑成型制备了再生纤维素纤维/PLA复合材料,并对这2种复合材料的性能进行了比较研究。结果表明,采用粘胶纤维或Lyocell纤维增强均可有效提高PLA复合材料的结晶度、力学性能和维卡软化温度。粘胶纤维的锯齿形截面有利于其与PLA基体的结合,因此粘胶纤维/PLA复合材料具有略高的冲击强度及拉伸强度。Lyocell纤维增强更有利于复合材料结晶度的提高,使得Lyocell/PLA复合材料具有更高的弹性模量和维卡软化温度。     

The effect of fibre sizing on fibres and bundle strength in hybrid glass carbon fibre composites

Tests have been carried out on single carbon fibres supplied in the sized and unsized conditions, as well as impregnated tows and tows in a glass–carbon fibre hybrid composite of the same fibre. The results were analysed using a Weibull distribution for the strengths of the reinforcing fibres and composites. The tensile strength of the single fibres appeared to be unaffected by the sizing of the filaments. In the case of the impregnated tows, an increase in characteristic strength of 7% was observed for the unsized fibres. The strength of the impregnated tows in hybrid composites was seen to be 15% higher than those tested in air. This can be attributed to the “hybrid effect”. This revised version was published online in November 2006 with corrections to the Cover Date.     

分级竹丝复合材料的原理与性质

竹子是性能最好的生物质材料之一, 其生长迅速、材料来源广泛, 成本低廉。竹材的结构是由竹纤维为主组成维管束, 维管束和薄壁细胞组成竹材。维管束在竹青一侧分布密集, 选择竹青片为原料可制作高性能的竹丝。竹丝的均齐性好, 具有良好的静态、抗冲击和抗疲劳性能。采用浸胶和预压方法制作预压料, 经过预压料的铺层, 热压压制, 可制成性能优良的分级竹丝复合材料。该材料的性能可达到或超过玻璃钢, 用于风轮叶片和船舶等重要工程。      

The effect of alkaline and silane treatments on mechanical properties and breakage of sisal fibers and poly(lactic acid)/sisal fiber composites

The main goals of this work were to study the effect of different chemical treatments on sisal fiber bundles tensile properties as well as on tensile properties of composites based on poly(lactic acid) (PLA) matrix and sisal fibers. For this purpose, sisal fibers were treated with different chemical treatments. After treating sisal fibers the tensile strength values decreased respect to untreated fiber ones, especially when the combination of NaOH + silane treatment was used. Taking into account fiber tensile properties and fiber/PLA adhesion values, composites based on silane treated fibers would show the highest tensile strength value. However, composites based on alkali treated and NaOH + silane treated fibers showed the highest tensile strength values. Finally, experimental tensile strength values of composites were compared with those values obtained using micromechanical models.     

玻璃纤维含量对竹粉/高密度聚乙烯复合材料性能的影响

为利用玻璃纤维提高木塑复合材料的综合性能,探讨玻璃纤维含量对竹粉/高密度聚乙烯(HDPE)复合材料性能的影响规律,首先,采用A-171硅烷偶联剂对竹粉表面进行了改性,并加入了一定量的玻璃纤维;然后,采用热压成型工艺制备了玻璃纤维-竹粉/HDPE复合材料;最后,考察了玻璃纤维含量对复合材料力学性能、热学性能及摩擦学性能的影响,并利用SEM观察材料的断面和磨损表面形貌。结果表明:当玻璃纤维含量为3wt%时,能显著提高竹粉/HDPE复合材料的拉伸强度和弯曲强度,与未添加玻璃纤维的复合材料相比,添加玻璃纤维后复合材料的拉伸强度和弯曲强度分别提高了19.41%和23.54%;在30~60℃温度范围内,复合材料长度-宽度方向上的线膨胀系数随着玻璃纤维含量的增加而明显减小,而同一复合材料的线膨胀系数随温度的升高而逐步增大;在氮气气氛下,随玻璃纤维含量的增加,竹粉/HDPE复合材料的摩擦系数先逐渐增大,而后基本保持不变,磨损率逐渐减小。所得结论显示玻璃纤维含量为3wt%~7wt%的木塑产品适用于建筑横梁(如凉亭或桥梁等),而玻璃纤维含量为7wt%~10wt%的木塑产品适用于高人流量场所(如公园或休闲绿道等)的地面铺装。      

甘蔗渣显微结构对聚乳酸/甘蔗渣复合材料结构与性能的影响

采用碱处理、硅烷偶联剂处理以及碱处理配合硅烷偶联剂处理等方式改性甘蔗渣(BF),采用傅里叶变换红外光谱(FTIR)、X射线衍射(XRD)、扫描电镜(SEM)、X射线光电子能谱(XPS)、热重分析(TGA)以及力学性能测试等研究改性后BF结构的变化。结果表明,不同改性方法均明显改变了BF的结构及改性剂的键合方式。碱处理能够去除BF中的半纤维素等小分子聚合物以及部分非晶区的纤维素,导致BF热稳定性降低,结晶度上升。碱液浓度偏高以及碱处理时间过长会导致BF的纤维表面原纤化,虽然能增加与偶联剂反应的面积,但BF的强度大大下降,不利于BF的增强作用。因此,硅烷偶联剂处理的BF/PLA复合材料的相容性及力学性能最佳,其次为碱处理配合硅烷偶联剂处理的BF/PLA复合材料,最后为碱处理的BF/PLA复合材料。     

Bamboo fiber reinforced thermoplastic molding made of steamed wood flour

To improve the mechanical property of moldings made of steamed wood flour, layered wood moldings reinforced with steam-exploded bamboo fiber was prepared. Setting the bamboo fiber weight fractions at 25, 50, and 75%, and number of layers at three-, five-, and seven-layered wood moldings were prepared by compression molding. The results of tensile test showed that the tensile strength as well as Young’s modulus increased along with the increase in the bamboo fiber fractions. Where the bamboo fiber content was 75%, the tensile strength became approximately 3.8 to 5.8 times greater, and the tensile Young’s modulus became approximately 2.5 times greater when compared to moldings of 100% wood flour. This fact shows that bamboo fiber is effective to improve the mechanical property of wood moldings. In addition, the tensile strength also increased as the number of layers increased. This result suggested that interfacial shear stress was produced between the layers of bamboo fiber and wood flour.     

Impedance-spectroscopy analysis of oriented and mercerized bamboo fiber-reinforced epoxy composite

Bamboo fiber-reinforced epoxy composites were fabricated with untreated and alkali treated bamboo fibers. Dielectric, electric modulus, ac, and dc conductivity studies were carried out to rationalize the dielectric behavior of bamboo/epoxy composites. Composites of two fiber orientation parallel and perpendicular to the electric field were prepared. The dielectric behavior and electric modulus spectra of the composites were characterized using standard impedance analyzer. Dielectric properties were analyzed as a function of frequency (95 Hz–2 MHz) for temperatures in the range from 30 to 180 °C. Real part of dielectric constant (ε′), conductivity, and dielectric dissipation factor (tan δ) of 0° oriented bamboo/epoxy composites were higher than that of 90° oriented composites. Conductivity activation energy, tan δ, ε′, and volume resistivity decreased with increase in frequency at all the temperatures under study. Mercerization reduces the water absorption in bamboo fibers and thus improves corresponding dielectric properties of composites. Relaxation times 39.80 μs and 258.5 μs for 0° and 90° oriented bamboo/epoxy composites were calculated respectively from the relaxation peaks observed in electric modulus spectra at 180 °C.     

PBS增韧改性MWNTs/PLA导电3D 打印耗材的制备及性能

为解决多壁碳纳米管/聚乳酸(MWNTs/PLA)导电打印耗材变脆的问题,本文利用双螺杆熔融共混方法,制备了聚丁二酸丁二醇酯(PBS)增韧改性的MWNTs/PLA复合材料。研究发现,PBS添加量对复合材料的性能有显著影响。随PBS含量增加,复合材料的电阻率升高,断裂伸长率和冲击强度明显提高,但拉伸强度、弯曲强度和硬度有所降低。当PBS含量为10%时,共混复合材料的综合性能最好,并根据最佳条件制成具有一定韧性的导电3D打印耗材,实际使用效果良好。