碳纤维/聚丙烯/聚乳酸增强复合材料的力学性能

为在不改变碳纤维/聚丙烯(PP)复合材料力学性能前提下,降低复合材料中PP含量以减轻环境降解压力,通过在碳纤维/PP复合材料树脂体系中掺杂可降解的聚乳酸(PLA)形成共混树脂体系,并经热压成型制备碳纤维增强共混树脂复合材料。探究了PLA、PP共混体系质量比对复合材料冲击、弯曲和拉伸性能的影响。结果表明:随着树脂体系中PLA质量分数的增加,复合材料的冲击强度和弯曲强度都呈先降低后升高、再降低的趋势,拉伸强度呈现先升高后降低的趋势;当PLA质量分数为60%时,复合材料的冲击强度和弯曲强度最高,分别为21.8 kJ/m²和112.5 MPa,拉伸强度为37.2 MPa,复合材料的综合物理力学性能最优,与未添加PLA的复合材料的力学性能相近。     

Hybrid Composites Made from Jute/Coir Fibers: Water Absorption,Thickness Swelling,Density, Morphology,and Mechanical Properties

The action of water in natural fiber-reinforced composite material was studied so as to produce great swelling with resultant changes in the fine structure, dimensional stability, and mechanical properties. Water absorption and thickness swelling test reveal that hybrid composite shows water absorption moderately, which is 15.3% for hybrid coir/jute/coir composite and 11.2% for hybrid jute/coir/jute composite. The thickness swelling, water absorption, and mechanical properties of the hybrid composites slightly increased as the layering pattern of hybrid composites changed. Hybridization of coir fibers composites with jute fibers can improve the dimensional stability, extensibility and density of pure coir composites. Microstructures of the composites were examined to understand the mechanisms for the fiber-matrix interaction in relation to mechanical properties.     

Impact of Pre‐Processing of Montmorillonite on the Properties of Melt‐Extruded Thermoplastic Starch/ Montmorillonite Nanocomposites

A simple and environmentally‐friendly processing method was used to prepare thermoplastic starch (TPS)/ montmorillonite (MMT) nanocomposites. X‐ray diffraction (XRD) and transmission electron microscopy (TEM) demonstrated that glycerol could enlarge the d‐spacing and destruct the layered structure of MMT effectively during the pre‐processing of MMT. So the enlarged d‐spacing and fragmentized platelets of glycerol activated‐MMT were a precondition to form intercalated or exfoliated TPS‐based nanocomposites during the melt extrusion processing. These highly dispersive and compatible TPS/activated‐MMT nanocomposites had increased thermal stability and tensile properties as compared with non‐activated composites. Especially, the tensile strength of nanocomposites could be enhanced to 8.6 MPa, the improvement was about two times the initial tensile strength of TPS.     

纳米纤维素增强可生物降解聚合物的研究进展

本文综述了纤维素纳米晶体(CNC)和纤维素纳米纤丝(CNF)在增强可生物降解聚合物中的研究进展.主要介绍了两种纳米纤维素及其制备方法,阐述了纳米纤维素的增强机理和复合材料的构筑方法,详细论述了纳米纤维素在增强聚乳酸(PLA)、热塑性淀粉(TPS)、聚己内酯(PCL)应用的研究进展.最后简要分析了纳米纤维素增强可生物降解...     

Study on the Pre-Treatment,Physical and Chemical Properties of Ramie Fibers Reinforced Poly (Lactic Acid) (PLA) Biocomposite

The comparative advantage of using vegetable fibers as reinforcement (fillers) attracted manufacturing industries over conventional composites. Natural fibers are purely green features that can easily decompose in a normal way to water and CO₂ when encountered with moisture during their disposal. In this research, the effect of pre-treatment and properties of ramie fibers reinforced polylactic acid (PLA) composite were studied. Before the composite preparation, ramie fibers were soaked in a solution of alkali (sodium hydroxide) and silane coupling agent to provide better compatibility between ramie fibers and PLA interface. Additionally, a design containing nine samples was conducted to study the effect of temperature, fiber volume ratio, molding pressure and time on composite fabrication. From the results, optimum processing parameters were identified based on the tensile, bending and impact strengths improvement from various tested samples. Furthermore, this study highlights the degradation process and properties of ramie fibers reinforced PLA composites by underground burial experimental procedures.     

Influence of microwave power on mechanical properties of microwave-cured polyethylene/coir composites

ABSTRACT

The present work deals with investigating the influence of microwave power on mechanical properties of 20 wt.% coir reinforced high-density polyethylene (HDPE) composites. Chopped coir/HDPE composites were fabricated using various microwave power levels (360 W, 540 W, 720 W and 900 W). The XRD analysis of the specimens reveals that crystallinity index in various specimens was in the range of 79.54% to 84.59%. The specimen cured at 360 W exhibited a maximum tensile strength of 29.5 ± 1.5 MPa, which is 28.26% greater than composite cured at 900 W (23 ± 1.5 MPa). Flexural strength of specimen cured at 360 W was maximum (37.74 ± 2 MPa).     

聚乳酸包覆相变材料复合织物的制备及其性能

利用静电纺丝法制备聚乳酸（PLA）包覆相变材料的纳米纤维膜,为了改善其与普通织物间的复合牢度,首先对其进行等离子体处理,再同粘胶、羊毛织物进行复合,探讨了等离子体处理复合织物前后及各材料之间在保温、透气透湿、拉伸强力和剥离强力方面的差异。结果表明：等离子体处理前后粘胶/PLA/羊毛复合织物的透气性低于羊毛织物,处理前后的透湿量较羊毛/ 粘胶复合织物分别降低76.5%和62.5%;拉伸强力高于PLA/相变材料纳米纤维膜;粘胶/PLA/羊毛复合织物经等离子体处理前后的克罗值比粘胶/羊毛复合织物分别提升了18.07%和17.78%;等离子体处理后的粘胶/PLA/羊毛复合织物在剥离强力性能上较处理前提升了34.4%.     

玻璃纤维增强复合材料在水环境中的性能

为了解玻璃纤维增强材料在水环境中的性能变化,利用真空辅助树脂注入方法制作了2层和3层的玻璃纤维/不饱和聚酯树脂复合材料板材。在经过一定时间蒸馏水的浸泡后,对材料的拉伸及弯曲性能进行了测试,并对经水浸泡前后复合材料的显微照片进行了分析。测试结果表明:随着浸泡时间的增加,材料的拉伸强度呈下降趋势;板材的弯曲强度也有一定程度的下降。     

The Tensile and Flexural Properties of Textile Composites

The mechanical properties of thermoset (glass-fibre-reinforced epoxy, polyester, and vinylester) and thermoplastic (glass-fibre-reinforced poly(ethylene terephthalate)) composite laminates manufactured from novel textile fabrics are investigated. The tensile and flexural properties of warp-knitted and woven composites were determined for glass-fibre-reinforced epoxy, polyester, and vinylester. The tensile strength and modulus were slightly lower than expected, mainly owing to fibre misalignment. The flexural failures of the thermoplastic laminates initiated on the compression face, and they were stable and gradual, i.e. a large amount of energy absorption was possible.

Thermoplastic and thermoset box-beams were manufactured by using compression moulding and resin-transfer moulding, respectively. Woven and warp-knitted fabrics, together with braiding, were used for the preforming. The load-bearing capabilities of the beams were tested in three-point bending. Failures initiated at the compression side of the beams, more noticeably so for the thermoplastic beams. The experimental results are compared with those of a finite-element analysis, and the agreement is reasonably good.     

玻璃纤维/聚丙烯纤维增强热塑复合材料的制备及其性能

为获得高质量比和高取向度的长纤维增强热塑性复合材料,通过牵切工艺将玻璃纤维和聚丙烯纤维混合成为须条,将须条正交铺层后用热压方法制备玻璃纤维/聚丙烯长纤维热塑性复合材料,然后对复合材料的形貌、力学性能和动态力学性能进行测试和分析。结果表明:复合材料中玻璃纤维的平均长度为22.9 mm,质量分数为45.73%,纤维伸直度高,取向度高,分散性好;基体材料能够充分浸润玻璃纤维,复合材料具有较小的孔隙率,其值为1.58%,且该复合材料比挤出模压得到的复合材料具有更好的力学性能;复合材料的玻璃化转变温度为73.4 ℃,在温度为150 ℃时,能够保持较高的储能模量和较小的损耗因子,具有良好的热力学性能。     

增塑体系对蔗渣基可生物降解复合材料性能的影响

利用甘油、甲酰胺和乙二醇对淀粉/蔗渣进行增塑改性,通过挤出注塑制备出了聚乳酸(PLA)/淀粉/蔗渣可生物降解复合材料。研究了增塑改性剂种类和含量对复合材料加工性能、流变性能、力学性能以及吸水性的影响。结果表明:选用的3种增塑剂对淀粉/蔗渣均有明显的增塑作用,且甲酰胺的增塑效果最好;当PLA、淀粉和蔗渣质量比为6:2:2时,增塑制得的复合材料的拉伸强度均在35 MPa以上;复合材料在4天后的吸水率均大于10%,其中由甲酰胺增塑复合材料的吸水率高达25%;增大增塑剂含量,有助于改善复合材料加工性能,但会增大复合材料的吸水率和降低复合材料的拉伸强度。     

Effect of Green Gram Husk Nanocellulose on Banana Fiber Composite

Nanocellulose is a significant bio entity in the present-day applications of nanocomposites. In this regard, the present work focuses on fabrication of green gram husk cellulose-based hybrid nanocomposites. In the process of nanocellulose extraction, residues obtained after each stage of treatment are characterized through physical and morphological tests. Later, nanocellulose is reinforced in unsaturated polyester with 1, 3, 5, and 7 wt. % to study the tensile properties. The peak tensile strength is found to be 39 MPa at 5wt% of cellulose nanocomposites. Noting the enhancement in tensile properties of nanocomposites, nanocellulose is reinforced in banana fiber composites and its influence on mechanical properties is studied. Nanocellulose/banana fiber hybrid composites showed enhanced tensile strength, flexural strength, and impact strength.     

制备工艺对黄麻/聚丙烯针织复合材料性能的影响

 本文讨论了不同工艺黄麻横机针织物增强聚丙烯复合材料的制备工艺对其力学性能的影响。首先利用针织的方法在横机上分别织造黄麻1+1罗纹、畦编、半畦编织物作为复合材料的增强体,分别以3层和5层进行同向铺层、不同质量配比与聚丙烯（PP）纤维均匀混合后通过热压工艺制成复合材料。对所制备的复合材料板材拉伸及弯曲性能进行测试与分析。研究结果表明：在复合织物均为1+1罗纹时,其复合板材性能以3层1+1罗纹6/4的配比为最佳;相同配比,相同层数情况下,畦编组织板材性能则最优;对于相同配比1+1罗纹板材3层性能优于5层。     

Thermoplastic Starch Processing and Characteristics—A Review

Canola Council of Canada, Winnipeg, Manitoba, Canada The rising costs of nonrenewable feedstocks and environmental concerns with their industrial usage have encouraged the study and development of renewable products, including thermoplastic starch (TPS). Starch is an abundant, plant-based biodegradable material with interesting physicochemical characteristics that can be exploited, and this has received attention for development of TPS products. Starch exhibits usable thermoplastic properties when plasticizers, elevated temperatures, and shear are present. The choice of plasticizer has an effect on TPS, even when these have similar plasticization principles. Most TPS have glass transition temperature, T_g, in the range of approximately ?75 to 10°C. Glassy transition of TPS is detected by differential scanning calorimeter (DSC) and thermodynamic analyzer (DMA), although DMA has been found to be more sensitive and effective. TPS has low tensile properties, typically below 6 MPa in tensile strength (TS). The addition of synthetic polymers, nanoclay, and fiber can improve TS and water-resistance ability. The moisture sorption behavior of TPS is described in GAB and BET models, from which monolayer moisture content and specific area are derived. Current studies on surface tension, gas permeability, crystallinity, and so on of the TPS are also reviewed.     

Effect of silica nanoparticles on mechanical properties of Kevlar/epoxy hybrid composites

The addition of nanofillers in high-performance reinforcement results in the formation of hybrid composites. The objective of this research is to determine the effect of silica nanofillers loading on the mechanical properties of Kevlar/epoxy composites for ballistic use. Produced hybrid composite laminates were tested for flexural properties, tensile Properties and impact energy absorption. DMA analyses were performed to investigate composite properties at elevated temperatures. It was observed that introduction of silica nanofillers enhanced flexural properties, tensile strength, and storage modulus of composites. Impact energy absorption was increased up to a specific extent of nanofiller addition. The findings of this study indicate that introduction of silica nanofillers on Kevlar fabrics is a promising method for enhancing mechanical properties of hybrid composite laminates.     

Fabrication and Characterization of MWCNT Filled Hybrid Natural Fiber Composites

Hybrid composites are fabricated by the combination of two or more fibers using a single matrix. It can be fabricated either with all of its constituents as natural fibers or with one or more constituents belonging to artificial fiber. The stacking sequence of the fibers in a hybrid composite can be altered resulting in a varying mechanical properties. In the present study the MWCNT filled banana-jute-flax fiber reinforced composites are investigated for its mechanical behavior by varying the stacking sequence of the fiber layers and weight % of Multi-Walled Carbon Nano Tube (MWCNT). A Modified resin was prepared by adding MWCNT in the epoxy resin using ultrasonic probe sonicator and a hybrid composite is fabricated with it by using compression moulding processes. The mechanical properties are evaluated as per the ASTM standards. The incorporating of MWCNT and the stacking sequence of fiber layers shows the greater impact on the mechanical properties. The composites of jute fibers at the extremities (JBFBFBFJ) exhibiting the enhancement of tensile, compressive and hardness properties than the flax fiber at the extremities (FBJBJBJF) and it could be used in various automobile applications. Microstructure of the samples are investigated by Scanning Electron Microscope (SEM)with Energy dispersive X-ray (EDS). The results indicate that increasing the weight % of MWCNT and varying the stacking sequence of fibers improves the mechanical properties of hybrid natural fiber composites.     

二维与三维机织复合材料力学性能的实验研究

对超厚三维正交机织复合材料及二维要织层合板人别进行了拉伸和压缩实验,研究比较了两种复合材料刚度和强度特性的差异研究发现无论是三维机织材料的拉压还是二维层合板的拉压应力应变曲线都近似为直线,而且具有脆性破坏的特点;三维复合材料的拉压强度要高于二维层合板.这主要是由于材料不同的增强相结构及纤维含量造成;不同的破坏模式对材料强度影响很大.     

硼酸交联对挤出吹塑变性淀粉/聚乙烯醇复合膜性能的影响

为了提高淀粉基复合膜的阻水性,拓宽淀粉膜的应用范围,以羟丙基二淀粉磷酸酯与聚乙烯醇(PVA)为成膜原料,硼酸为交联剂,采用挤出吹塑工艺制备了淀粉/PVA复合膜。分析了粒料的流变性能,研究了淀粉膜的交联密度、力学性能、阻隔性能、疏水性能以及微观形貌等性质。结果表明,随着硼酸添加量的增加,淀粉/PVA复合材料的熔体流动性下降,淀粉/PVA复合膜的阻氧、阻水性能增强,而淀粉膜的抗拉强度和拉伸模量呈降低趋势,断裂伸长率先升高后降低。添加1%的硼酸,淀粉/PVA复合膜的表面更加均匀平整,疏水性最强,具有最小的溶胀度、最大的凝胶质量和最高的交联密度。     

Thermoplastic Starch–PVA Nanocomposite Films Reinforced with Nanocellulose from Oil Palm Empty Fruit Bunches (OPEFBs): Effect of Starch Type

ABSTRACT

This research studied the effect of three types of starch on the properties of thermoplastic starch (TPS)–Poly (vinyl alcohol) (PVA)–cellulose nanocomposite films. Three different types of starch with amylose and amylopectin contents used were corn starch, cassava starch, and sago starch. Meanwhile, the nanocellulose was isolated from oil palm empty fruit bunches (OPEFBs) by mechanical treatment using ultrafine grinder. The nanocomposite films were made by evaporation casting method. It was found that the difference of amylose content in the native starch affected the properties of nanocomposite films. Meanwhile, the nanocellulose added into matrix TPS–PVA could increase tensile strength of TPS–PVA nanocomposite films.     

玻璃纤维多轴向经编复合材料的制备及拉伸性能研究

以环氧树脂为基体,分别以玻璃纤维多轴向经编针织物和玻璃纤维机织物作为增强材料,通过手糊法制备复合材料,并通过试验对比研究两种复合材料的拉伸性能。结果表明,经编复合材料沿各个轴向的拉伸强度比复合前多轴向经编针织物及机织复合材料的强度均有明显提高,增幅均在50%以上,说明多轴向经编复合材料具有更优异的力学性能。这为进一步扩大玻璃纤维多轴向经编复合材料的应用领域提供了有力证据。