Mechanical and water absorption behaviour of banana/sisal reinforced hybrid composites

The tensile, flexural, impact and water absorption tests were carried out using banana/epoxy composite material. Initially, optimum fiber length and weight percentage were determined. To improve the mechanical properties, banana fiber was hybridised with sisal fiber. This study showed that addition of sisal fiber in banana/epoxy composites of up to 50% by weight results in increasing the mechanical properties and decreasing the moisture absorption property. Morphological analysis was carried out to observe fracture behaviour and fiber pull-out of the samples using scanning electron microscope.     

Woven hybrid biocomposites: Dynamic mechanical and thermal properties

The dynamic mechanical and thermal analysis of oil palm empty fruit bunch (EFB)/woven jute fibre (J_w) reinforced epoxy hybrid composites were carried out. The storage modulus (E′) was found to decrease with temperature in all cases, and hybrid composites had showed better values of E′ at glass transition temperature (T_g) compared to EFB and epoxy. Loss modulus showed shifts in the T_g of the polymer matrix with the addition of fibre as reinforcing phase, which indicate that fibre plays an important role in case of T_g. The Tan δ peak height was minimum for jute composites and maximum for epoxy matrix. Complex modulus variations and phase behaviour of the hybrid composites was studied by Cole-Cole analysis. Thermal analysis result indicates an increase in thermal stability of EFB composite with the incorporation of woven jute fibres. Hybridization of EFB composite with J_w fibres enhanced the dynamic mechanical and thermal properties.     

Reinforcing potential of micro- and nano-sized fibers in the starch-based biocomposites

Starch-based biocomposites reinforced with jute (micro-sized fiber) and bacterial cellulose (BC) (nano-sized fiber) were prepared by film casting. Reinforcement in the composites is essentially influenced by fiber nature, and amount of loading. The optimum amount of fiber loading for jute and bacterial cellulose in each composite system are 60 wt% and 50 wt% (of starch weight), respectively. Mechanical properties are largely improved due to the strong hydrogen interaction between the starch matrix and cellulose fiber together with good fiber dispersion and impregnation in these composites revealed by SEM. The composites reinforced with 40 wt% or higher bacterial cellulose contents have markedly superior mechanical properties than those reinforced with jute. Young’s modulus and tensile strength of the optimum 50 wt% bacterial cellulose reinforced composite averaged 2.6 GPa and 58 MPa, respectively. These values are 106-fold and 20-fold more than the pure starch/glycerol film. DMTA revealed that the presence of bacterial cellulose (with optimum loading) significantly enhanced the storage modulus and glass transition temperature of the composite, with a 35 °C increment. Thermal degradation of the bacterial cellulose component occurred at higher temperatures implying improved thermal stability. The composites reinforced with bacterial cellulose also had much better water resistance than those associated with jute. In addition, even at high fiber loading, the composites reinforced by bacterial cellulose clearly retain an exceptional level of optical transparency owing to the effect of the nano-sized fibers and also good interfacial bonding between the matrix and bacterial cellulose.     

Woven hybrid composites: Tensile and flexural properties of oil palm-woven jute fibres based epoxy composites

In this research, tensile and flexural performance of tri layer oil palm empty fruit bunches (EFB)/woven jute (Jw) fibre reinforced epoxy hybrid composites subjected to layering pattern has been experimentally investigated. Sandwich composites were fabricated by hand lay-up technique in a mould and cured with 105 °C temperatures for 1 h by using hot press. Pure EFB and woven jute composites were also fabricate for comparison purpose. Results showed that tensile and flexural properties of pure EFB composite can be improved by hybridization with woven jute fibre as extreme woven jute fibre mat. It was found that tensile and flexural properties of hybrid composite is higher than that of EFB composite but less than woven jute composite. Statistical analysis of composites done by ANOVA-one way, it showed significant differences between the results obtained. The fracture surface morphology of the tensile samples of the hybrid composites was performed by using scanning electron microscopy.     

单向连续碳纤维-玻璃纤维层间混杂增强环氧树脂基复合材料的力学性能

为了研究连续单向纤维的层间混杂方式对复合材料力学性能及破坏方式的影响,采用碳纤维-玻璃纤维体积比为1∶1,以拉-挤成型法制备了具有不同层间混杂结构的连续单向纤维增强环氧树脂基复合材料,并研究了不同层间混杂结构的连续单向碳纤维-玻璃纤维增强环氧树脂基复合材料的力学性能及破坏形式。结果表明：具有层间混杂结构的复合材料抗拉强度处于纯碳纤维/环氧树脂复合材料和纯玻璃纤维/环氧树脂复合材料之间,复合材料的拉伸断裂方式为劈裂;具有层间混杂结构的复合材料的层间剪切强度均优于纯碳纤维/环氧树脂复合材料和纯玻璃纤维/环氧树脂复合材料,复合材料的剪切断裂方式为层间断裂。     

Effect of jute and kapok fibers on properties of thermoplastic cassava starch composites

Since mechanical properties and water uptake of biodegradable thermoplastic cassava starch (TPCS) was still the main disadvantages for many applications. The TPCS matrix was, therefore, reinforced by two types of cellulosic fibers, i.e. jute or kapok fibers; classified as the low and high oil absorbency characteristics, respectively. The TPCS, plasticized by glycerol, was compounded by internal mixer and shaped by compression molding machine. It was found that water absorption of the TPCS/jute fiber and TPCS/kapok fiber composites was clearly reduced by the addition of the cellulosic fibers. Moreover, stress at maximum load and Young’s modulus of the composites increased significantly by the incorporation of both jute and kapok fibers. Thermal degradation temperature, determined from thermogravimetric analysis (TGA), of the TPCS matrix increased by the addition of jute fibers; however, thermal degradation temperature decreased by the addition of kapok fibers. Functional group analysis and morphology of the TPCS/jute fiber and TPCS/kapok fiber composites were also examined using Fourier Transform Infrared Spectroscopy (FTIR) and Scanning Electron Microscopy (SEM) techniques.     

Permeability and mechanical properties of plant fiber reinforced hybrid composites

Plant fibers with small diameter generally possess high mechanical properties, while their permeability was relatively low compared to those with large diameter. By hybridizing these two kinds of plant fibers, a composite with both high permeability and good mechanical properties can be achieved. Here, permeability of jute/ramie and ramie fabrics were compared, regarding the flow rate of a vinyl ester resin during the Vacuum-Assisted Resin Transfer Molding process; and mechanical properties of their composites were addressed thereafter. The faster flow rates of vinyl ester resin proved that jute/ramie fabrics were more permeable than pure ramie fabrics resulting from larger flow space and the greater capillary effect of jute fabrics. Both tensile strength and Charpy impact strength of the hybrid composites dropped slightly after hybridization due to the lower properties of jute than of ramie fiber as the properties of fiber dominated the failure mode. However, interlaminar shear strength remained, since the middle layer was far from the weak jute–ramie interface. The results implicated a method to improve the permeability of plant fiber reinforcement when manufacturing efficiency is considered in industrial application.     

黄麻纤维毡的表面处理及其增强聚丙烯复合材料的力学性能

提出了一种新的纤维表面处理方法和工艺, 将MPP 乳液引入黄麻纤维的表面处理。考察了NaOH 处理对黄麻纤维吸湿性和热稳定性的影响, 研究了NaOH 溶液及NaOH 溶液和MPP 乳液组合处理对黄麻纤维毡增强聚丙烯复合材料力学性能的影响。结果表明: 黄麻经NaOH 处理后, 吸湿率降低, 热稳定性提高; 黄麻纤维毡增强聚丙烯复合材料的力学性能明显提高, 表面涂覆MPP 乳液后, 力学性能更进一步改善。      

Natural fabric sandwich laminate composites: development and investigation

In this work, eco-friendly natural fabric sandwich laminate (NFSL) composites are formulated using jute and linen-fabric-reinforced epoxy with different layer ratios (5:0, 4:1, 3:2, 2:3, 1:4 and 0:5) by hand layup system. Different mechanical attributes (tensile, flexural and impact) of the NFSL composites are quantified. Thermal stability and water absorption behaviour of the NFSL composites are also assessed. A scanning electron microscope (SEM) and optical microscope are used for qualitative analysis of NFSL composites’ interfacial properties. Two layers of jute and three layers of linen sandwich laminate have registered peak values in tensile and impact properties. The five layers of linen laminate composite have exhibited high flexural strength, been proven to have good thermal stability and furthermore shown better water absorption behaviour than any other laminate composites.     

黄麻纤维/环氧复合材料及其性能分析

本文研究了黄麻单向纤维和随机分布短纤维增强环氧树脂复合材料的制作和拉伸、压缩、弯曲、层间剪切以及冲击性能,并讨论了它的破坏机理与微观形貌。黄麻纤维本身性能优异,并且具有优于其它天然植物纤维的可纺性。黄麻纤维复合材料的优异性能具有进一步研究开发的潜力。     

Investigations on the fabrication and the characterization of glass/epoxy,carbon/epoxy and hybrid composites used in the reinforcement and the repair of aeronautic structures

This paper reports the fabrication and the characterization of glass/epoxy, carbon/epoxy and hybrid laminated composites used in the reinforcement and/or the repair of aeronautic structures. These composites were manufactured by the hand lay-up process. Their physical, thermal and mechanical behaviors are discussed in terms of moisture absorption, thermal stability, tensile strength, elastic modulus, flexural strength, flexural modulus and abrasive wear resistance. The impact of hygrothermal aging on the mechanical properties of each composite group has been also investigated.The main results indicated that after water immersion, all composites showed significant moisture absorption especially for glass/epoxy composite. Thermogravimetric analysis showed that the hybrid composite presented the best thermal stability behavior while the glass/epoxy composite the bad behavior. The mechanical properties of the carbon/epoxy composites, in the bulk material, were considerably higher than those of the glass/epoxy; the hybrid structure presented intermediate mechanical properties. The same trend was also observed in terms of wear properties. Finally, a deleterious effect on the strength of all composites due to hygrothermal exposure was established. However, carbon/epoxy composites seem to be less susceptible to aging damage after 90 days at 90 °C.     

Mechanical properties of epoxy composites with high contents of nanodiamond

Mechanical properties and thermal conductivity of composites made of nanodiamond with epoxy polymer binder have been studied in a wide range of nanodiamond concentrations (0-25 vol.%). In contrast to composites with a low content of nanodiamond, where only small to moderate improvements in mechanical properties were reported before, the composites with 25 vol.% nanodiamond showed an unprecedented increase in Young’s modulus (up to 470%) and hardness (up to 300%) as compared to neat epoxy. A significant increase in scratch resistance and thermal conductivity of the composites were observed as well. The improved thermal conductivity of the composites with high contents of nanodiamond is explained by direct contacts between single diamond nanoparticles forming an interconnected network held together by a polymer binder.     

Low velocity impact properties of intra-ply hybrid composites based on basalt and nylon woven fabrics

In this paper, the low velocity impact behavior of homogenous and hybrid composite laminates reinforced by basalt–nylon intra-ply fabrics was experimentally investigated. Epoxy resin was used as matrix material. The purpose of using this hybrid composite is to combine the good mechanical properties of basalt fiber with the excellent impact resistant of nylon fiber. Five different types of woven fabrics were used as reinforcement with different volume percentages of nylon (0%, 25%, 33.3%, 50% and 100%). The effect of nylon/basalt fiber content on maximum force, maximum deflection, residual deflection, total absorbed energy, elastic energy, size and type of damage were studied at several low velocity impact nominal energy levels (16, 30 and 40 J). The results indicate that impact performance of these composites is significantly affected by the nylon/basalt fiber content. The visual inspection and ultrasonic C-scan of the impact damaged specimens reveals that content of nylon/basalt fiber controls the type and size of damage.     

阻燃级黄麻短纤维/聚乳酸复合材料的制备及性能研究

采用具有良好降解性的黄麻短纤维作为增强材料,生物可降解材料聚乳酸作为基体,制备了可降解的黄麻/聚乳酸复合材料。对复合材料的力学性能,耐热性能以及阻燃性能等进行了测试,结果表明,相对与纯聚乳酸,黄麻纤维的加入使复合材料的力学性能和耐热性能有明显提高,阻燃体系的加入使复合材料具有良好的阻燃性能,可达到UL94V0级,但阻燃剂的加入一定程度上降低了复合材料的力学性能及热变形温度。     

Influence of hygrothermal environment on thermal and mechanical properties of carbon fiber/fiberglass hybrid composites

The absorption and diffusion of water in a carbon fiber/glass fiber hybrid composite was investigated. Water-sorption experiments, mechanical property tests and dynamic mechanical analysis (DMA) were performed after immersion in water at different temperatures for up to 32 weeks. The moisture uptake mechanism exhibited by the hybrid fiber system was determined to be more complex than the single fiber type. Weight-change profiles for the composites fitted the theoretical Fickian diffusion curve during the initial immersion time, but diverged substantially as time progressed. The shear properties and the glass transition temperature (T_g) were sensitive to the effects of hygrothermal environment, and values for both decreased with increasing water uptake. Microscopic inspection of water-soaked samples showed no cracking when the absorption was less than saturation. The thermal and mechanical properties were mostly retained (after drying), provided the moisture absorption did not exceed the saturation point.     

Determination of mechanical properties of intra-layer abaca–jute–glass fiber reinforced composite

Composites made with natural fibers are finding applications in a wide variety of engineering fields due to their low cost and eco-friendly nature. This paper deals with the fabrication and evaluation of hybrid natural fiber composite using jute and abaca fibers along with glass fibers. Each composite is made up of five layers with three layers of jute and abaca enclosed by two layers of glass fibers. The composites are manufactured with three different fiber orientations and the compositions are varied in three different proportions. The fabricated composite samples are tested to investigate their various mechanical properties. From the test results, it is observed that fiber orientation plays a vital role in determining the mechanical properties of the composite. Morphological analysis is done using Scanning Electron Microscope (SEM).     

Effects of diammonium phosphate on the flammability and mechanical properties of bio-composites

The flammability, thermal stability and mechanical properties of natural fiber-reinforced thermoplastic bio-composites were measured using a horizontal burning test, thermogravimetric analyzer, and universal testing machine, respectively. The composites were fabricated from film resins (Polylactic-acid, PLA and Polypropylene, PP) and natural fibers (coconut filter and jute fiber) by a hot press machine. To improve the flame retardancy of the bio-composites, various diammonium phosphates (DAP) were treated into the fibers. In general, the results indicate that increasing the percentage of DAP used to treat the fibers effectively improves the flame resistant, weight loss rate, and flexural modulus but decreases the flexural and tensile strengths of the bio-composites. Bio-composites with DAP-treated fibers showed a greater flexural modulus than those with untreated fibers, and the flexural modulus was even greater than that of neat polymers (PLA and PP). Also, increasing the percentage of DAP for treatment of the fibers in the composites decreases the temperature required for 5% weight loss and the decomposition rate, but increases the char residual at 500 °C. The best linear burning rate and weight loss rate were observed for fiber treatment with 5% DAP. The compressive and wear properties of these bio-composites were also studied.     

The effect of thermoplastic coating on the mechanical properties of woven fabric carbon/epoxy composites

The effect of a polyetherimide (PEI) coating on the mechanical properties of woven fabric carbon/epoxy composites was investigated by thermal mechanical analysis, fractographical analysis and mechanical properties measurements. PEI coating enhanced the mechanical properties of carbon/epoxy composites mainly through the improvement of matrix properties. This was because most of the PEI coated on the carbon fiber diffused into the bulk of epoxy matrix due to its good miscibility with epoxy resin. As for mechanical properties of woven fabric carbon/epoxy composites, the extent of improvement by PEI coating highly depended on the applied stress state. Among the mechanical properties, mode II delamination resistance of carbon/epoxy composites showed the highest increment because matrix shear property played an important role in delamination resistance of woven fabric carbon/epoxy composite. Because of the woven geometry of carbon fiber, the improvement in impact property of carbon/epoxy composite was trivial except the large amount of PEI coated case.     

Influence of fiber content on the mechanical and dynamic mechanical properties of glass/ramie polymer composites

The combination of glass and ramie fibers with a polyester matrix can produce a hybrid material that is competitive to all glass composites (e.g. those used in the automobile industry). In this work, glass and ramie fibers cut to 45 mm in length were used to produce hybrid polymer composites by resin transfer molding (RTM), aiming to evaluate their physical, mechanical and dynamic mechanical properties as a function of the relative glass–ramie volume fractions and the overall fiber content (10, 21 and 31 vol.%). Higher fiber content and higher ramie fiber fraction in the hybrid composites yielded lower weight composites, but higher water absorption in the composite. The mechanical properties (impact and interlaminar shear strength) of the composites were improved by using higher fiber content, and the composite with 31 vol.% of reinforcement yielded the lowest value for the reinforcement effectiveness coefficient C, as expected. Although the mechanical properties were improved for higher fiber content, the glass transition temperature did not vary significantly. Additionally, as found by analyzing the adhesion factor A, improved adhesion tended to occur for the composites with lower fiber content (10%) and higher ramie fiber fraction (0:100) and the results for the adhesion factor A did not correspond to those found by the analysis of the tan delta peak height.     

Development and material properties of new hybrid medium density fibreboard from empty fruit bunch and rubberwood

In this research, new hybrid medium density fibreboard (MDF) was produced by using rubberwood (RW) and empty fruit bunch (EFB) based on oven-dried weight. There are two different ratios of hybrid MDF from rubberwood and EFB were produced which are EFB:RW, 20:80 and EFB:RW, 50:50 at 65% and 93% relative humidity (RH). The effect of storage time and relative humidity on the mechanical and physical properties of new hybrid MDF was studied. It was found that at 93% relative humidity, new hybrid MDF exhibited a highest effect on the mechanical and physical properties of panel after 10 weeks storage time. It observed that, hybrid MDF with ratio of EFB:RW, 20:80 exhibited the highest mechanical (flexure test and internal bonding) and physical properties [moisture content (MC), thickness swelling (TS), water absorption (WA)] as compared to hybrid MDF produced from EFB:RW, 50:50. Thus, the result showed that addition of higher amount of EFB fibres in hybrid MDF will decreased the composites properties. The property of composites decreases with increase of relative humidity and storage time. The result showed that, at 65% humidity new hybrid MDF exhibited lower effect on mechanical and physical properties of the panel.