IFSS, TG, FT-IR spectra of impregnated sugar palm (Arenga pinnata) fibres and mechanical properties of their composites

This study aimed to investigate the effect of resin impregnation on the interfacial shear strength (IFSS), thermogravimetric (TG) and fourier transform infrared (FT-IR) of sugar palm (Arenga pinnata) fibres. In addition, the effect of resin impregnation on the mechanical properties of sugar palm fibre reinforced unsaturated polyester (UP) composites was also studied. The fibres were impregnated with UP via vacuum resin impregnation process at a pressure of 600 mmHg for 5 min. Composites of 10, 20, 30, 40 and 50 % fibre loadings were fabricated and tested for tensile and flexural properties. It was observed that the impregnation process caused the fibres to be enclosed by UP resin and this gave a strong influence to the increase of its interfacial bonding by the increase of its IFSS from single fibre pull-out test. It was also observed with TG and FT-IR spectra that the impregnated fibre had lower moisture uptake than the control and there was no significant increase in thermal stability of the impregnated fibre. The sequence of fibre decomposition started from the evaporation of moisture, hemicelluloses, cellulose, lignin and finally ash content and the presence of these components were proven by FT-IR spectra. For the composite specimens, due to the high interfacial bonding of the impregnated fibre and the matrix, the impregnated composites showed consistently higher tensile strength, tensile modulus, elongation at break, flexural strength, flexural modulus and toughness than the control samples. It was also observed that 30 % fibre loading gave optimum properties.     

五种植物纤维粉填充不饱和聚酯树脂复合材料的性能对比

以芝麻秸秆粉、水稻秸秆粉、玉米芯秆粉、菠萝叶粉、甘蔗渣粉五种不同植物纤维粉为填充体、不饱和聚酯树脂(UPR)为基体制作植物纤维粉/UPR复合材料,对比研究了秸秆种类对复合材料密度、力学性能及吸水性能的影响。结果表明,植物纤维粉粒径为100目、添加量为UPR用量的10%时,芝麻秸秆粉/UPR复合材料的综合力学性能最好,拉伸强度、弯曲强度和冲击强度分别为41.320 MPa、67.467 MPa和2.815 KJ/m^2,且每一浸泡阶段吸水率均最低。     

原位合成纳米SiO2增强阴离子聚酯型上浆剂及其对碳纤维复合材料层间剪切强度的影响

采用溶胶-凝胶法, 在侧链带有羧基的线性不饱和聚酯中加入正硅酸乙酯(TEOS), 使TEOS在酸性条件下发生水解反应, 原位合成纳米SiO₂增强阴离子型聚酯乳液(SEAPE). 利用傅里叶变换红外光谱(FTIR)仪、 激光粒度分析仪和冷冻扫描电子显微镜(Cryo-SEM)对SEAPE进行分析与表征. 将SEAPE与聚乙二醇单油酸酯润滑剂、 非离子型表面活性剂FC-4430及抗氧剂1010进行复配, 原位制备纳米SiO₂增强阴离子型聚酯乳液上浆剂(SEAPEs), 用扫描电子显微镜(SEM)、 视频动态接触角测量仪、 X射线能谱(EDS)仪和纤维强力仪对SEAPEs上浆后碳纤维的表面形貌、 表面能、 碳纤维(CF)表面元素及碳纤维增强不饱和聚酯(UPR)复合材料(CF/UPR)的层间剪切强度(ILSS)进行测试与表征. 结果表明, 当TEOS添加质量分数为5%时, SEAPEs上浆后的碳纤维有效增强了其与UPR的结合强度, CF/UPR复合材料的ILSS达到40.03 MPa, 与市售环氧树脂型上浆剂上浆后碳纤维增强UPR复合材料相比, ILSS提高90.1%. SEAPEs中原位生成的纳米SiO₂分散均匀, 乳液储存稳定, 上浆后SiO₂均匀吸附在碳纤维表面, 增加碳纤维表面能, 改善碳纤维与树脂间的浸润性, 可有效提高碳纤维增强不饱和聚酯树脂复合材料的ILSS.     

Synthesis and Characterization of Polyester-Based Nanocomposite

Recently, unsaturated polyester resin (UPR) and silica nanocomposite prepared by mechanical process is the one of the promising composite materials. In this study, the effects of silica as filler on mechanical, thermal, and morphological properties of unsaturated polyester-based composite were investigated. Mechanical properties such as tensile strength, elongation and Young's modulus increase with the addition of silica nanoparticle up to 1.0 wt%, and then decrease, over 1.0 wt%. Morphological surface of composite reveals that well-dispersed silica in the matrix occurred in low concentration. However, increasing of silica concentration causes aggregation of particles. Enhancement of mechanical properties strongly corresponds to strong adhession force of silica with the matrix and it influnced by well-disperse silica particles on the whole surface of composite. Thermal characterization and analysis of major functional group of the composites were also performed and described in this paper.     

Effect of wood sawdust filler on the mechanical properties of Indian mallow fiber yarn mat reinforced with polyester composites

The research article focused on the effect of wood sawdust as secondary filler reinforcement in Indian mallow fiber yarn mat reinforced with polyester composites. Composites were fabricated along the transverse and longitudinal orientation in six different combinations by compression molding machine. The mechanical properties of composites by single and double layer yarn mat with and without wood sawdust filler were evaluated while loading composites specimen on warp and weft direction at the first time in this research paper. The Indian mallow fiber double layer longitudinal orientation yarn mat/wood sawdust filler/polyester composite specimen along the warp direction was found to exhibit optimum mechanical properties compared to other composites. Furthermore, the Indian mallow fiber yarn mat composites were fabricated with helmet and civil construction pipes at first time in this work to replace the synthetic fiber through natural fiber. Scanning electron microscopy was performed to study the morphologies of internal crack and fractured surface of composites.     

Mechanical Behavior of Unidirectional Curaua Fiber and Glass Fiber Composites

Summary: This work intends to promote the use of natural fibers by comparing the behavior of isophthalic polyester matrix composites reinforced with unidirectional curaua fibers with that of unidirectional glass fiber composites. The composites were produced varying the reinforcement angle (0°, 15°, 30°, 45°, 60°, 75° and 90°) with the aim of studying the fiber orientation effect on composite strength. Composites were also made varying the fiber volume fraction (10%, 20%, 30%, 40% and 50%). The efficiency of an alkaline (5% NaOH) surface treatment of the curaua fiber was also evaluated. The unidirectional composites were characterized using tensile, flexural and short beam tests as per ASTM standards. The properties of a lamina reinforced with either glass or curaua fibers were also studied using theoretical micromechanical approach available in commercial software. The curaua fiber alkaline treatment produced higher tensile strength results compared with untreated fibers. The increase in reinforcement angle significantly decreased strength and modulus of the composites, as expected, and the glass fiber composites showed a more pronounced dependence with fiber orientation. Although the glass fiber laminas showed the best mechanical performance, the results obtained with the curaua fibers were considered similar for angles greater than 45°.     

Improving hydrophobicity and compatibility between kenaf fiber and polymer composite by surface treatment with inorganic nanoparticles

Compatibility of natural fiber with hydrophobic matrix is a herculean task in literature works. Surface treatment is a well-known approach for increasing the strength of interfacial adhesion between fibres and polymer matrices. Therefore, this study aims to examine the impact of surface treatment with zinc oxide nanoparticles (ZnONPs) in improving hydrophobicity of kenaf fiber (KF) to enhance the compatibility between KF and polymer matrix. In this study, KF reinforced unsaturated polyester composites (KF/UPE) were fabricated by the hand lay-up method with varying fiber loadings (wt %) of 10 20, 30, and 40. KF were treated with five different contents of ZnONPs (1% to 5 wt%) to make UPE/KF-ZnONPs composites. The composites were studied in terms of wetting response (contact angle measure and water absorption), mechanical properties, chemical structure (FTIR), crystalline structure (XRD), and surface morphology (SEM, AFM). The investigational findings indicate that the composite samples incorporating ZnONPs exhibit optimum hydrophobicity and mechanical properties, as they possessed a higher contact angle than the untreated KF composite. The optimum content of ZnONPs was found to be 2 wt%. Regarding water absorption, the untreated UPE/KF composites absorbed more water than the treated UPE/KF-ZnONPs composites. SEM images showed changes in the morphology of the KF, while FTIR analysis proved the presence of ZnONPs functional groups in the UPE/KF composites. AFM images revealed that the ZnONPs could actively produce nanolevel roughness, advantageous to the hydrophobic characteristics.     

Mechanical Properties,Water Absorption,and Chemical Resistance of Napier Grass Fiber Strand–Reinforced Epoxy Resin Composites

Napier grass fiber strands were used as reinforcement to obtain composites with epoxy resin as matrix. To improve the surface, these fiber strands were treated with alkali solution. The composites were prepared by means of hand lay-up molding, then the effects of Napier grass fiber strand loading on mechanical properties such as tensile, flexural and impact, interfacial bonding, and chemical resistance were investigated. The composite with 20 wt.% Napier grass fiber strands gives excellent mechanical properties and chemical resistance, showing that it has the best bonding and adhesion of the composites. SEM micrographs of fractured and worn surfaces clearly demonstrate the interfacial adhesion between fiber and matrix. Alkali-treated Napier grass fiber strand–reinforced composites have better resistance to water and chemicals than the untreated fiber strand composites.     

Critical aspects related to processing of carbon nanotube/unsaturated thermoset polyester nanocomposites

Carbon nanotubes (CNTs) have outstanding mechanical, thermal and electrical properties. As a result, particular interest has been recently given in exploiting these properties by incorporating carbon nanotubes into some form of matrix. Although unsaturated polyesters with styrene have widespread use in the industrial applications, surprisingly there is no study in the literature about CNT/thermoset polyester nanocomposite systems. In the present paper, we underline some important issues and limitations during the processing of unsaturated polyester resins with different types of carbon nanotubes. In that manner, 3-roll mill and sonication techniques were comparatively evaluated to process nanocomposites made of CNTs with and without amine (NH₂) functional groups and polyesters. It was found that styrene evaporation from the polyester resin system was a critical issue for nanocomposite processing. Rheological behaviour of the suspensions containing CNTs and tensile strengths of their resulting nanocomposites were characterized. CNT/polyester suspensions exhibited a shear thinning behaviour, while polyester resin blends act as a Newtonian fluid. It was also found that nanotubes with amine functional groups have better tensile strength, as compared to those with untreated CNTs. Transmission electron microscopy (TEM) was also employed to reveal the degree of dispersion of CNTs in the matrix.     

Interacting blends of Styrenated unsaturated poly (ester–amide)s with commercial unsaturated polyester resin (o-phthalic anhydride based)

Unsaturated poly (ester–amide)s resins (UPEAs) were prepared by the reaction between an epoxy resin, namely diglycidyl ether of bisphenol-A (DGEBA) and unsaturated aliphatic bisamic acids (B_1–4) using a base catalyst. These UPEAs were then diluted by styrene and blended with commercial unsaturated polyester resin (o-phthalic anhydride based) to produce a homogeneous resin. The curing of these Styrenated UPEAs–UPR blends was carried out using Benzoyl peroxide (BPO) as a catalyst and N,N′-Dimethyl aniline (DMA) as a promoter. The glass fiber reinforced composites (i.e. laminates) of these Styrenated UPEAs–UPR (o-phthalic anhydride based) blends were fabricated. The mechanical and chemical resistance properties of the glass fiber composites have also been evaluated. The unreinforced cured samples of the Styrenated UPEAs–UPR (o-phthalic anhydride based) blends were also analyzed by thermogravimetry (TGA).     

Grass fiber reinforced phenol formaldehyde resin composite: preparation,characterization and evaluation of properties of composite

There is a growing interest in the development of new materials through utilization of natural resources. This paper describes evaluation of water leached and alkali treated chopped grass fiber reinforced phenol formaldehyde composite. Here alkali treatment of grass fiber was carried out by varying the concentration of sodium hydroxide. The thermal stability of the composite was assessed by thermogravimetric analysis (TGA). Fourier transformation infrared spectroscopic study of both water leached and alkali treated grass fiber‐phenolic resin composite was also performed. Water absorption and swelling behavior of grass fiber phenolic resin composites in water were studied and the alkali treated grass fiber‐resin composite showed less water absorption and swelling. A composite prepared from 1% alkali treated grass fiber and 55% resin, showed the highest tensile strength whereas a composite prepared from 5% alkali treated grass fiber and 55% resin, showed maximum flexural properties. Copyright © 2006 John Wiley & Sons, Ltd.     

Thermogravimetric analysis of aluminised E-glass fibre reinforced unsaturated polyester composites

Novel aluminised E-glass fibre reinforced unsaturated polyester composites, originally formulated for enhanced thermal and electrical shielding properties were evaluated in terms of their thermal performance. The thermal degradation of these specimens was analysed using a thermogravimetric analyser (TGA). The samples were heated from ambient temperature to 500 °C at a heating rate of 20 °C/min. All specimens were decomposed under dry nitrogen (N₂) at a flow rate of 40 ml/min to yield gases and solid char. Aluminised E-glass composites were compared alongside the unmetallised E-glass and unreinforced composite. The major weight loss occurred between 200 and 400 °C. The unreinforced polyester had a maximum weight loss, 1.25%/°C, occurring at 360 °C. For the aluminised and unmetallised E-glass composites, the maximum rate of weight loss was 0.34 and 0.55%/°C, respectively. Experimental results show the degradation of the aluminised E-glass composites obtained from TGA tests is higher compared to those of unmetallised E-glass fibre and unreinforced polyester composite. This improvement is correlated to the aluminium coating.     

Mechanical properties of hybrid glass/sugar palm fibre reinforced unsaturated polyester composites

A research has been carried out to investigate the mechanical properties of composites made by hybridizing sugar palm fibre (Arenga pinnata) with glass fibre into an unsaturated polyester matrix. Hybrid composites of glass/sugar palm fibre were fabricated in different weight ratios of strand mat glass fibres: sugar palm fibres 4:0, 4:1, 4:2, 4:3, 4:4, and 0:4. The hybrid effects of glass and sugar palm fibre on tensile, flexural and impact properties of the composites were evaluated according to ASTM D5083, ASTM D790 and ASTM D256 respectively. Results have been established that properties of hybrid glass/sugar palm composites such as tensile strength, tensile modulus, elongation at break, toughness, flexural strength, flexural modulus and impact strength are a function of fibre content. The failure mechanism and the adhesion between fibres/matrix were studied by observing the scanning electron micrographs of impact fracture samples. In general, the incorporation of both fibres into unsaturated polyester matrix shows a regular trend of increase in the mechanical properties.     

The effect of granite powder on mechanical,structural and water absorption characteristics of alkali treated cordia dichotoma fiber reinforced polyester composite

Environmental and societal concerns such as pollution, disposal of solid waste, requirement of different conflicting properties for materials in varied applications and cost are the main reasons for the development of new materials from the existing materials. The concerns may possibly be overcome by substituting natural fibers for synthetic fibers. In this study, a hybrid composite was developed by reinforcing the natural fiber “cordia dichotoma” and filler “granite powder” into polyester resin. This composite was fabricated using hand lay-up method. Cordia dichotoma fibers were surface treated with NaOH for reducing the hydrophilic nature of the fiber. Unused industrial waste in the form of granite powder obtained from the granite polishing industry is utilized as reinforcement in polymer composite. The hybrid composite was prepared by reinforcing a constant cordia dichotoma fiber content of 20 wt % and varying the granite powder weight (wt. %) percentages (0, 5, 10, 15, and 20) into polyester resin. Mechanical properties (tensile, flexural and impact) of hybrid composites were investigated. The novelty of this work lies in utilization of granite powder sourced from industrial waste utilized as filler material. Granite, as one of the hard materials, may improve wear and other mechanical properties. Following the results obtained, granite powder could be evidenced as a good filler material for the betterment of composites mechanical properties. Also, the ability of this filler material is proved in decreasing water absorption and chemical resistance. Scanning electron microscope (SEM) analysis was performed to investigate the bonding and distribution of granite powder within both the fiber as well as resin in the composite. Besides, the presence of chemical functional groups in the composite was traced by Fourier transform Infrared spectroscopy (FTIR). Also, Thermo-gravimetric analysis (TGA) was carried out and the composite was found to be thermally stable up to 415 °C.     

Mechanical properties of UV‐curable carbon fiber‐reinforced polymer composite patch: Repair evaluation of damaged aluminum alloy

Epoxy resin composite patches reinforced by carbon fiber were prepared through ultraviolet (UV)–curing method, and the damaged aluminum alloy plates are rapidly repaired by means of adhesively bonding method. Mechanical properties of the composite patches and damaged aluminum alloy plates before and after repair were studied by experiment and numerical simulation. Results indicated that the tensile properties of carbon fiber/epoxy resin composite patches presented the tendency of first increase and then decrease with the increase of layer numbers of reinforced fiber. The composite patches with two layers fiber showed the best tensile properties, and the tensile strength and modulus reached 1.13 GPa and 27.79 GPa, respectively. However, the bending strength of composite patches decreased with the increase of layer numbers. Results of performance evaluation on the mechanical properties of damaged aluminum alloy plates repaired by the two layers carbon fiber/epoxy resin composite patches showed that the repair efficiency of tensile and bending properties of the repaired aluminum alloys reached more than 83% and 160%, respectively, compared with the undamaged aluminum alloys. Besides, results of numerical simulation showed that the stress intensity factor (SIF) of the crack tip on repaired aluminum alloy plates decreased significantly in comparison with the unrepaired aluminum alloy plates, which further revealing the reinforced mechanism of composite patches on the bending properties of repaired aluminum alloy plates.     

Influence of particle size and particle loading on mechanical and dielectric properties of biochar particulate-reinforced polymer nanocomposites

This research work emphasizes using pulverized biochar obtained by the pyrolysis of rice husk as a particulate reinforcement in unsaturated polyester matrix. The influence of particle size and particle loading on the mechanical and dielectric properties of particulate composites were investigated. The mean size of particles obtained through pulverizing using ball mill varied from 510 to 45 nm when milled for a duration ranging from 6 to 30 h. The particle loading in the composite varied from 0.5 to 2.5 wt%. The impact strength of the specimen having particle loading of 2.5 wt% with 45 nm particle size increased by 77.50%, and its dielectric constant increased by 7% when compared to that of cured pure resin; however, the tensile strength decreased. The biochar particles were subjected to X-ray diffraction, Fourier transform infrared spectroscopy (FT-IR), and atomic force microscopy (AFM) analysis for characterization. Morphological studies were performed on tested samples by scanning electron microscope.     

Effect of alkali treatment on mechanical and thermal properties of Kenaf fiber-reinforced thermoplastic polyurethane composite

In this study, a composite of thermoplastic polyurethane reinforced with short Kenaf fiber (Hibiscus cannabinus) was prepared via melt-blending method using Haake Polydrive R600 internal mixer. Effect of various sodium hydroxide NaOH concentrations, namely 2, 4 and 6% on tensile, flexural and impact strength was studied. Mean values were determined for each composite according to ASTM standards. Tensile, flexural and impact strength negatively correlates with higher concentrations of NaOH. Scanning electron microscope (SEM) was used to examine the surface of both treated and untreated fibers as well as fracture surface of tensile specimens. Morphology of treated and untreated fibers showed a rougher surface of treated fibers. It also showed that some of high concentrations of NaOH treated fibers have NaOH residues on their surface. This was confirmed by energy dispersive X-ray point shooting performed on the same SEM machine. Morphology of surface of fracture indicated that untreated composite had a better adhesion. Treated and untreated fibers as well as composites were characterized using Fourier transform infrared spectroscopy (FTIR). FTIR of treated fibers showed that NaOH treatment resulted in removal of hemicelluloses and lignin. FTIR also showed that untreated composite has more H-bonding than all treated composites. Thermal characteristic studies using thermogravimetry analysis and differential scanning calorimetry showed that untreated composite was more thermally stable than treated composites.     

Resin impregnation of cellulose nanofibril films facilitated by water swelling

Flexible composite films were produced by impregnating aqueous phenol formaldehyde (PF) resin into water-swollen cellulose nanofibril (CNF) films. CNF films were prepared using a pressurized filtration method in combination with freeze drying. The freeze-dried films were swollen with water then impregnated with PF resin by soaking in aqueous resin solutions of varying concentrations. Small amounts of PF slightly enhanced the tensile properties of CNF films. The formulation with the best mechanical properties was CNF/PF films with 8 wt % resin exhibiting tensile stress and toughness of 248 MPa and 26 MJ/m³, respectively. Resin concentrations higher than about 8 % resulted in composites with decreased tensile properties as compared to neat CNF films. The wet strength of the composite films was significantly higher than that of the neat CNF films. The resulting composites showed greater resistance to moisture absorption accompanied by reduced thickness swelling when soaked in water as compared to neat CNF films. The composites also showed decreased oxygen permeability at low humidity compared to neat films, but the composites did not show improved barrier properties at high humidity.     

Seawater ageing of flax/poly(lactic acid) biocomposites

Natural fibre reinforced biopolymer composites, or biocomposites, are an alternative to the glass fibre reinforced thermoset composites widely used today in marine applications. Biocomposites offer good mechanical properties and total biodegradability, but if they are to be adopted for marine structures their durability in a seawater environment must be demonstrated. In the present study unreinforced PLLA (Poly(l-Lactic acid)), injected and film stacked flax composites with the same PLLA matrix have been examined. All the samples were aged in natural seawater at different temperatures in order to accelerate hygrothermal ageing. Changes to physico-chemical and mechanical behaviour have been followed by weight measurements, thermal and gel permeation chromatography (GPC) analyses, and tensile testing, completed by acoustic emission recording and scanning electron microscopy (SEM) examination. The matrix tensile stiffness is hardly affected by seawater at temperatures to 40 °C but the composite loses stiffness and strength. Fibre/matrix interface weakening is the main damage mechanism induced by wet ageing, but both matrix and fibre cracks also appear at longer periods.     

Influence of Nanoclay on the Mechanical Performance of Wild Cane Grass Fiber-Reinforced Polyester Nanocomposites

Natural fiber-reinforced nanocomposites were prepared by incorporating wild cane grass fiber and organically modified montmorillonite (MMT) nanoclay into polyester resin. The composites were formulated up to a maximum volume of fiber of approximately 40% and their mechanical properties were investigated. The mean tensile strength and tensile modulus of nanoclay-filled wild cane grass fiber composites are 6.3% and 18.3% greater than those of wild cane grass fiber composites, respectively, without addition of nanoclay at maximum percentage volume of fiber. The mean flexural strength of nanocomposites at maximum percentage volume of fiber was increased to a maximum of 221 Mpa and flexural modulus to 4.2 Gpa. The mean impact strength of nanoclay-filled wild cane grass fiber composites was increased to 376.7 J/m at maximum percentage volume of fiber. The weight loss of nanoclay-filled wild cane grass fiber/polyester composites was 30% and 22% less than that of composites without nanoclay at maximum percentage volume of fiber. The results indicated that the use of nanoclay showed significant improvement in all the mechanical properties of wild cane grass fiber-reinforced composites.