麻纤维强化复合材料的制备及性能研究

采用注塑法以热塑性淀粉(TPS)、聚丁二酸丁二醇酯(PBS)为基体,麻纤维为填料制备复合材料。研究了麻纤维含量、处理方式及种类对复合材料力学性能和吸水性能的影响。结果表明:复合材料的拉伸强度和弯曲强度值随着麻纤维量(0.5%~2%)增加而增加,断裂伸长率先增加后减小,吸水量逐渐降低;经丙烯酸处理的纤维强化后材料力学性能和吸水性能要优于碱、亚氯酸钠和苯甲酰氯;大麻强化的材料力学性能要强于苎麻和黄麻纤维,而苎麻纤维强化的材料吸水性能要弱于大麻和黄麻纤维。     

改性大麻纤维/不饱和聚酯复合材料的力学性能及界面表征

采用模压成型方法制备大麻纤维/不饱和聚酯复合材料,用六亚甲基二异氰酸酯(DIH)与丙烯酸羟乙酯(HEA)对纤维进行表面处理。结果表明,纤维改性后复合材料的拉伸强度、弯曲强度及弯曲模量均有显著提高;当DIH-HEA用量为纤维干质量的3%时,复合材料的总体力学性能最佳。复合材料拉伸断面扫描电镜(SEM)显示,纤维表面处理改善了纤维与树脂间的界面结合。改性纤维的红外光谱(FT-IR)和X射线光电子能谱(XPS)分析表明,DIH-HEA混合物与纤维表面羟基产生共价键结合。     

竹纤维/不饱和聚酯复合材料拉伸强度及断面图像特征

研究纤维形态和表面处理对竹纤维/不饱和聚酯复合材料拉伸强度的影响及断面图像差分刺激特征。结果表明,纤维形态对复合材料拉伸强度有显著影响。化学浆纤维和竹原纤维增强复合材料的拉伸强度显著高于竹粉与机械浆纤维增强的复合材料。竹纤维经1,6-己二异氰酸酯与2-羟乙基丙烯酸酯改性后,复合材料拉伸强度显著提高。纤维处理前复合材料拉伸断面图像差分刺激角度值的直方图高度明显高于处理后的,拉伸断面电镜图像差分刺激角度值反映了复合材料拉伸强度的差异。     

表面改性和混杂对超高分子量聚乙烯纤维/环氧树脂复合材料性能的影响

采用紫外接枝和与芳纶纤维混杂的方式改善UHMWPE纤维的缺点,详细研究了接枝单体种类、浓度和纤维混杂等对UHMWPE纤维/环氧树脂复合材料性能的影响。结果表明,以丙酮为溶剂采用一步接枝法在紫外光辐射下将丙烯酸接枝到UHMWPE纤维表面上,可显著提高UHMWPE纤维增强的复合材料的弯曲强度、冲击强度和拉伸强度;随着接枝单体浓度的提高弯曲强度和冲击强度没有明显的变化,而拉伸强度不断提高。同时,将UHMWPE纤维与芳纶纤维混杂可提高其与树脂基体生成的复合材料的耐热性。UHMWPE纤维与芳纶纤维按1∶1的质量比混杂,混杂纤维增强的复合材料在90℃的形变量比UHMWPE纤维增强的复合材料减少66.7%,显著提高了复合材料的耐热性。     

木纤维增强不饱和聚酯复合材料的性能研究

采用丙烯酸(AA)对木纤维表面进行改性处理,并对改性后的木纤维进行悬浮性测试。将改性处理后的木纤维与不饱和聚酯树脂复合,制备了木纤维增强不饱和聚酯复合材料,对其进行了拉伸和冲击等力学性能测试。结果表明:木纤维含量对复合材料的力学性能影响很大。随着木纤维含量的增加,复合材料的延伸率和拉伸强度均有所提高;当木纤维含量为15%时,改性处理试剂的最佳浓度为0.15mol/L。此时,材料的延伸率和拉伸强度增加的幅度均趋于平稳,力学性能变化不明显。     

Technora纤维表面等离子体处理对其复合材料界面性能的影响

用扫描电子显微镜观察Technora纤维表面物理形貌并测量单丝纤维的拉伸强度以分析等离子体处理对纤维本体性能的影响,再用层间剪切强度和吸水率分别表征复合材料在室温干态和高温湿态下的界面性能,研究了等离子体处理对Technora纤维复合材料界面性能的影响。结果表明,用等离子体处理后纤维表面的物理形貌发生了显著变化,复合材料的层间剪切强度由未处理时的15.74 MPa提高到24.93 MPa,提高的幅度高达58.4%;同时,复合材料的吸水率下降而本体性能基本不受影响。上述结果表明,等离子体对Technora纤维的表面改性能有效地改善其复合材料的界面性能。     

苎麻纤维表面处理对其复合材料性能的影响

在不同处理时间和功率的条件下,对苎麻纤维表面进行冷等离子体处理。通过分析纤维表面能以及纤维拉伸强度的变化,选取了3组处理纤维与未处理纤维作为复合材料的增强纤维,并且运用模压工艺制备苎麻纤维增强复合材料。经过扫描电镜分析、弯曲强度和剪切强度测试以及单纤维断裂实验,探究了冷等离子体处理对苎麻纤维表面性能及其复合材料性能的影响。结果表明:冷等离子体处理去除了苎麻纤维表面的胶质和杂质,提升了纤维与环氧树脂的粘附功。随着处理时间与功率的增加,复合材料板的力学性能随之提升。与未处理纤维复合材料相比,当处理条件为3min、200W时,复合材料的弯曲强度与剪切强度分别提升了37.0%和30.5%。     

亚麻落麻纤维增强可降解复合材料的拉伸强度预测

采用非织造结合热压成型工艺制备了亚麻落麻纤维增强聚乳酸(PLA)基可降解复合材料(亚麻落麻/PLA),研究了纤维体积分数对材料拉伸强度的影响,并利用 Kelly-Tyson拉伸强度预测模型及相关修正理论,提出了非连续植物纤维增强可降解复合材料(D-NFRBC)强度预测模型,该模型考虑了纤维长度、取向角、直径、强度概率分布及材料界面剪切强度与材料中纤维临界长度、纤维极限拉伸强度三者间制约关系对复合材料强度的影响。结果表明;亚麻落麻/PLA拉伸强度在纤维体积分数为39.6%时达到最大,应用本文建立的强度预测模型所得亚麻落麻/PLA拉伸强度预测值与实验值吻合良好。     

CaCl1和多巴胺处理对芳纶纤维表面结构与性能的影响

采用氯化钙(CaCl2)乙醇溶液和多巴胺水溶液浸渍法对芳纶纤维表面进行改性处理,对改性后芳纶纤维表面的化学结构、微观形貌、表面粗糙度、单丝拉伸强度和芳纶纤维/环氧树脂复合材料的界面性能等进行了测试分析.结果表明,采用CaCl2乙醇溶液处理芳纶纤维后,芳纶纤维表面有刻蚀出的沟槽,表面粗糙度增大,芳纶纤维/环氧树脂复合材料的层间剪切强度明显提高,同时由于纤维结构受到破坏,单丝拉伸强度下降了11.12％;采用多巴胺水溶液处理时,芳纶纤维表面沉积了聚多巴胺涂层,表面粗糙度增大,芳纶纤维/环氧树脂复合材料的层间剪切强度进一步提高,纤维结构几乎不受影响,单丝拉伸强度降幅较小;采用CaCl2乙醇溶液和多巴胺水溶液先后处理芳纶纤维后,纤维表面的聚多巴胺涂层更致密,复合材料的层间剪切强度达到最大值,同时改性后的纤维具有一定的抗紫外性能,此方法改性效果最优.     

玻璃纤维/大麻纤维增强聚丙烯混杂复合材料的力学性能和断裂特征(英文)

目前在土木工程,建筑,汽车等领域里使用的复合材料中,玻璃纤维是用量最大的增强材料。由于保护地球环境的呼声日趋高涨,天然纤维被期待着代替源于石油而且再利用困难的玻璃纤维,成为绿色复合材料的必要材料之一。本文通过注射成型工艺制作了玻璃短纤维,大麻短纤维以及混杂型纤维增强复合材料,并在拉伸实验中应用两种不同频率的声发射技术检测了拉伸断裂特性。实验发现,随着大麻纤维的加入和混杂复合材料绿色度的增加,复合材料的拉伸弹性模量随之线性增大,而拉伸强度基本保持不变。当大麻纤维的含量超过20wt%的时候,拉伸强度开始降低。在不同频率的声发射实验中,混杂型复合材料的声发射事件的产生都比单一纤维增强型复合材料要来的晚,也就是说,纤维的混杂有助于推迟微裂纹的产生。     

Chemical modification of kenaf fibers

The interest in using natural fibers in composites has increased in recent years due their lightweight, non-abrasive, combustible, non-toxic, low cost and biodegradable properties. However, lack of good interfacial adhesion, low melting point and poor resistance to moisture absorption make the use of natural fiber reinforced composites less attractive. Chemical treatment of the fiber can clean the fiber surface, chemically modify the surface, stop the moisture absorption process and increase the surface roughness. In this study, kenaf bast fibers, supplied by MARDI, for use in fiber-reinforced composites, were modified using NaOH of different concentrations. Morphological and structural changes of the fibers were investigated using scanning electron microscopy (SEM). A series of fiber bundle tensile tests were also performed to evaluate the effect of the treatments on the fiber tensile strength. It has been found that the alkalization treatment has improved the mechanical properties of the kenaf fiber significantly as compared to untreated kenaf fiber. It is also interesting to note that 6% NaOH yields the optimum concentration of NaOH for the chemical treatment.     

A study of the mechanical properties of short natural-fiber reinforced composites

The degree of fiber–matrix adhesion and its effect on the mechanical reinforcement of short henequen fibers and a polyethylene matrix was studied. The surface treatments were: an alkali treatment, a silane coupling agent and the pre-impregnation process of the HDPE/xylene solution. The presence of Si–O–cellulose and Si–O–Si bonds on the lignocellulosic surface confirmed that the silane coupling agent was efficiently held on the fibres surface through both condensation with cellulose hydroxyl groups and self-condensation between silanol groups.

The fiber–matrix interface shear strength (IFSS) was used as an indicator of the fiber–matrix adhesion improvement, and also to determine a suitable value of fiber length in order to process the composite with relative ease. It was noticed that the IFSS observed for the different fiber surface treatments increased and such interface strength almost doubled only by changing the mechanical interaction and the chemical interactions between fiber and matrix.

HDPE-henequen fiber composite materials were prepared with a 20% v/v fiber content and the tensile, flexural and shear properties were studied. The comparison of tensile properties of the composites showed that the silane treatment and the matrix-resin pre-impregnation process of the fiber produced a significant increase in tensile strength, while the tensile modulus remained relatively unaffected. The increase in tensile strength was only possible when the henequen fibers were treated first with an alkaline solution. It was also shown that the silane treatment produced a significant increase in flexural strength while the flexural modulus also remained relatively unaffected. The shear properties of the composites also increased significantly, but, only when the henequen fibers were treated with the silane coupling agent. Scanning electron microscopy (SEM) studies of the composites failure surfaces also indicated that there is an improved adhesion between fiber and matrix. Examination of the failure surfaces also indicated differences in the interfacial failure mode. With increasing fiber–matrix adhesion the failure mode changed from interfacial failure and considerable fiber pull-out from the matrix for the untreated fiber to matrix yielding and fiber and matrix tearing for the alkaline, matrix-resin pre-impregnation and silane treated fibers.     

Surface modification and adhesion mechanisms in woodfiber-polypropylene composites

The interfacial adhesion between wood fiber and thermoplastic matrix polymer plays an important role in determining the performance of wood-polymer composites. The objectives of this research were to elucidate the interaction between the anhydride groups of maleated polypropylene (MAPP) and hydroxyl groups of wood fiber, and to clarify the mechanisms responsible for the interfacial adhesion between wood fiber and polypropylene matrix. The modification techniques used were bulk treatment in a thermokinetic reactive processor and solution coating in xylene. FT-IR was used to identify the nature of bonds between wood fiber and MAPP. IGC and wood veneer pull-out test was used to estimate the interfacial adhesion. Mechanical properties of injection molded woodfiber-polypropylene composites were also determined and compared with the results of esterification reaction and interfacial adhesion tests. Confocal Microscopy was employed to observe the morphology at the wood fiber-polypropylene interface, and the dispersion and orientation of wood fiber in the polypropylene matrix, respectively. The effectiveness of MAPP to improve the mechanical properties (particularly the tensile strength) of the composites was attributed to the compatibilization effect which is accomplished by reducing the total wood fiber surface free energy, improving the polymer matrix impregnation, improving fiber dispersion, improving fiber orientation, and enhancing the interfacial adhesion through mechanical interlocking. There was no conclusive evidence of the effects of ester links on the mechanical properties of the composites.     

Effects of chemical treatments of hybrid fillers on the physical and thermal properties of wood plastic composites

Hybrid filler reinforced composites are considered as a high performance materials, but limited numbers of researches on hybridizations of wood fibers and mineral fillers were reported. Generally, high amount of filler content in composites can lead to the reduction of interfacial adhesion between matrix polymer and fillers, and it limits their applications. In this study, we measured the changes of tensile strength, water absorption, and thermal properties of composites after chemical treatments to wood fibers and mineral fillers. Coupling agent had its own optimum amount for wood fibers and talc to obtain the highest tensile strength. Talc addition showed little effect of the tensile strength with alkali treated wood fibers. Talc addition and silane treatment showed opposite effects on water absorption. Melting enthalpy was decreased by addition of the fillers because of the reduced amount of the crystallizable resin and because of the interference of the fillers for crystallization process.     

Effect of Seawater and Warm Environment on Glass/Epoxy and Glass/Polyurethane Composites

A study of the durability of fiber reinforced polymer (FRP) materials in seawater and warm environment is presented in this paper. The major objective of the study is to evaluate the effects of seawater and temperature on the structural properties of glass/epoxy and glass/polyurethane composite materials. These effects were studied in terms of seawater absorption, permeation of salt and contaminants, chemical and physical bonds at the interface, degradation in mechanical properties, and failure mechanisms. Test parameters included immersion time, ranging from 3 months to 1 year, and temperature including room temperature and 65°C. Seawater absorption increased with immersion time and with temperature. The matrix in both composites was efficient in protecting the fibers from corrosive elements in seawater; however moisture creates a dual mechanism of stress relaxation—swelling—mechanical adhesion, and breakdown of chemical bonds between fiber and matrix at the interface. It is observed that high temperature accelerates the degradation mechanism in the glass/polyurethane composite. No significant changes were observed in tensile strength of glass/epoxy and in the modulus of both glass/epoxy and glass/polyurethane composites. However, the tensile strength of the glass/polyurethane composite decreased by 19% after 1 year of exposure to seawater at room temperature and by 31% after 1 year of exposure at 65°C. Plasticization due to moisture absorption leads to ductile failure in the matrix, but this can be reversed in glass/polyurethane composites after extended exposure to seawater at high temperature where brittle failure of matrix and fiber were observed.     

Surface treatment of coir (Cocos nucifera) fibers and its influence on the fibers’ physico-mechanical properties

Coir, an important lignocellulosic fiber, can be incorporated in polymers like polyacrylate in different ways for achieving desired properties and texture. But its high level of moisture absorption, poor wettability and insufficient adhesion between untreated fiber and the polymer matrix lead to debonding with age. In order to improve the above qualities, adequate surface modification is required. In our present work, fiber surface modification by ethylene dimethylacrylate (EMA) and cured under UV radiation. Pretreatment with UV radiation and mercerization were done before grafting with a view to improve the physico-mechanical performance of coir fibers’. The effects of mercerization on shrinkage and fiber weight losses were monitored at different temperature and alkali concentration. We observed that, fiber shrinkage is higher at low temperature and 20% alkali treated coir fibers yielded maximum shrinkage and weight losses. It was found that higher shrinkage of the polymer grafted fiber showed enhanced physico-mechanical properties. The grafting of alkali treated fiber shows an increase of polymer loading (about 56% higher) and tensile strength (about 27%) than 50% EMA grafted fiber. The fiber surface topology and the tensile fracture surfaces were characterized by scanning electron microscopy and were found improved interfacial bonding to the modified fiber–matrix interface.     

Mechanical property improvement of unsaturated polyester composite reinforced with admicellar-treated sisal fibers

Sisal fiber was treated by admicellar polymerization with a poly(methyl methacrylate) film coating in order to enhance the interfacial adhesion of the fiber/polymer composite for mechanical property improvement. Properties of the admicellar-treated sisal fiber were investigated by measuring its moisture absorption and electrostatic charge. Thermal stability study by thermogravimetric analysis and film identification by FTIR was also carried out. The treatment was shown to improve the tensile and flexural properties, impact strength, and hardness of the composite. SEM micrographs of the tensile fracture surface of sisal/unsaturated polyester composites also show interfacial adhesion improvement of the composite prepared with admicellar-treated sisal.     

天然细菌纤维素增强不饱和聚酯树脂复合材料的制备及性能

将天然纤维-细菌纤维素（BC）作为增强材料加入不饱和聚酯树脂（UPR）基体中,采用RTM工艺制备BC/UPR复合材料,并对其力学性能、吸湿性能进行了研究。通过紫外辐照方法探讨了BC/UPR复合材料的降解性能。研究结果表明:通过对细菌纤维素的表面改性,在亲水性的天然纤维和疏水性的高聚物基体之间形成了化学键结合,提高了BC/UPR复合材料的力学性能;BC纤维体积分数的增加也有助于提高力学性能, 当纤维体积分数为20%时,该复合材料拉伸强度最高可达152.9MPa; BC/UPR复合材料的吸湿过程符合Fick定律,吸湿可导致力学性能下降; BC/UPR复合材料吸收光能后,表面含氧官能团数量增加,发生一定程度的光降解。      

Effect of glass fiber hybridization on properties of sisal fiber–polypropylene composites

Natural fiber reinforced polymer composites became more attractive due to their light weight, high specific strength, and environmental concern. However, some limitations such as low modulus, poor moisture resistance were reported. This study aimed to investigate the effect of glass fiber hybridization on the physical properties of sisal–polypropylene composites. Polypropylene grafted with maleic anhydride (PP-g-MA) was used as a compatibilizer to enhance the compatibility between the fibers and polypropylene. Incorporating glass fiber into the sisal–polypropylene composites enhanced tensile, flexural, and impact strength without having significant effect on tensile and flexural moduli. In addition, adding glass fiber improved thermal properties and water resistance of the composites.     

不同纤维织物/乙烯基酯复合材料的湿热老化

本文将不同纤维织物与750HOI环氧乙烯基酯树脂复合成三种层合结构的复合材料,对比研究了树脂浇铸体及复合材料在60℃与90℃去离子水中的湿热性能。通过材料的吸湿特性、弯曲性能、微观结构以及动态热机械性能的变化,分析了材料的湿热老化机理。研究表明:不同纤维织物增强的复合材料吸湿行为具有较大差异;90℃浸泡2160h后,添加碳纤维表面毡的复合材料F2弯曲强度保留率为70.42%,而表面层为方格布的复合材料J的保留率为51.88%;红外光谱(FTIR)研究表明:90℃湿热老化后复合材料基体树脂发生了水解断裂;扫描电镜(SEM)和动态热机械分析(DMA)研究发现:老化后复合材料中纤维/基体界面发生脱粘破坏,界面结合强度降低,试样的Tg和储能模量减小。