Hybrid effect in the mechanical properties of jute/rockwool hybrid fibres reinforced phenol formaldehyde composites

This research work was concerned with the evaluation of the effect of fibre content on the mechanical properties of composites. Composites were fabricated using jute/phenol formaldehyde (PF), rockwool/PF, and jute/rockwool hybrid PF with varying fibre loadings. Jute and rockwool fibre reinforced PF composites were fabricated with varying fibre loadings (16, 25, 34, 42, 50, and 60 vol.%). The jute/rockwool hybrid PF composites were manufactured at various ratios of jute/rockwool fibres such as 1:0, 0.92:0.08, 0.82:0.18, 0.70:0.30, 0.54:0.46, 0.28:0.72, and 0:1. Total fibre content of the hybrid composites was 42 vol.%. The results showed that tensile strength of the composite increased with increasing fibre content up to 42 vol.% over which it decreased for jute and rockwool fibre reinforced PF composites. Flexural strength of the composite was noted to peak at a fibre loading of 42 vol.% for jute/PF composites, and 34 vol.% for rockwool/PF composites. Impact strength of jute/PF composites increased with increasing fibre loading but that of rockwool/PF composites decreased at higher (>34 vol.%) fibre loadings. Tensile, flexural, and impact strengths of jute/PF composites were found to be higher than those of rockwool/PF composites. The maximum hardness values were obtained 42 vol.% for jute/PF composite, and 34 vol.% for rockwool/PF composite. Further increase in fibre loading adversely affected the hardness of both composites. For jute/rockwool hybrid PF composites, tensile and impact strengths decreased with increasing rockwool fibre loading. The maximum flexural strength of jute/rockwool hybrid PF composites was obtained at a 0.82:0.18 jute/rockwool fibre ratio while maximum hardness was observed at a 0.28:0.72 jute/rockwool fibre ratio. The fractured surfaces of the composites were analysed using scanning electron microscope in order to have an insight into the failure mechanism and fibre/matrix interface adhesion.     

Effect of hybrid ratio and laminate geometry on compressive properties of carbon/glass hybrid composites

Intra-layer and inter-layer hybrid composite laminates were made with epoxy resin and compositions were varied in six different proportions. In-plane compressive mechanical properties were studied using finite element analysis and experiments, and the results found were in good agreement. Properties of intra-layer and inter-layer hybrids were compared with plain carbon/epoxy and plain glass/epoxy composites, and a comparison among themselves was also made. It was found that intra-layer hybrids to some extent exhibit better compressive properties compared to inter-layer hybrids. Percentage enhancement in compressive failure strain was noticed. Negative hybrid effects on compressive strength was noticed for both intra-layer and inter-layer hybrid configurations. It was found that proportion of carbon fiber content plays a key role in determining the compressive properties. According to macro-scale observation all composite laminates failed catastrophically under compressive loading. SEM observation depicted that under compressive loading carbon fibers break first followed by glass fiber.     

Mechanical and water absorption properties of woven jute/banana hybrid composites

This work aims to predict the mechanical properties of woven jute/banana hybrid composite. Woven fabrics are arranged in three layers of different sequence. Resin used in this work is Epoxy LY556 with hardener HY951. Composite specimen are prepared by hand-layup techniques. The effect of layering sequence on the mechanical properties namely tensile, flexural and impact was analysed. It is found that the tensile and flexural strength of hybrid composite (Banana/Jute/Banana) is higher than that of individual composites. Similarly, the impact strength of Jute/Banana/Jute hybrid composite is better than other types of composite. It is found that the moisture absorption of woven banana fiber composite is lesser than the hybrid composite. Fractography study of the fractured specimen is carried out using scanning electron microscope to analyse the fracture behaviour of the hybrid composite.     

The evaluation of the thermal and mechanical properties of aramid/semi-carbon fibers hybrid composites

In this research work, aramid and semi-carbon fibers (SCFs) were hybridized in the form of interlayer or layer by layer into epoxy matrix by hand lay-up method. Afterward, the effect of hybridization on the thermal and mechanical properties of epoxy composites was characterized by thermal analysis; horizontal burning; tensile and bending tests. Based on the results of the mechanical tests, increasing SCFs to aramid fibers ratio decreased tensile strength, elastic and flexural modulus. But with increasing this ratio to 53 % failure strain reduced, whereas in the ratios of more than 53 %, the failure strain enhanced. The results of thermal analysis curves indicated that there are three stage mass loss at the temperature ranges of 100-220, 270-470 and 500-620 °C. It was also found that with increasing the SCFs to aramid fibers ratio decreased the third-stage of the mass loss. The results of horizontal burning showed that increasing the SCFs to aramid fibers ratio decreased the rate of burning.     

Surface treatments of jute fabric: The influence of surface characteristics on jute fabrics and mechanical properties of jute/polyester composites

In this study, jute fabrics were modified by alkali, micro-emulsion silicon (MS) and fluorocarbon based agents (FA) in order to enhance the interfacial adhesion between the polyester matrix and the jute fiber. X-ray photoelectron spectroscopy (XPS) and contact angle measurements were used to characterize fiber surfaces. The effects of various surface treatments on the mechanical and morphological of jute/polyester composites were also studied. All surface treatments were shown to improve the tensile, flexural strengths and interlaminar shear strengths of the composites. Moreover, the maximum improvement in the mechanical properties was obtained for the FA treated jute/polyester composites. SEM micrographs of the tensile fracture surface of jute/unsaturated polyester composites also exhibited improvement of interfacial and interlaminar shear strengths by the alkali, MS and FA treatments of jute fibers.     

Enhanced mechanical and thermal properties of hybrid graphene nanoplatelets/multiwall carbon nanotubes reinforced polyethylene terephthalate nanocomposites

The effects of graphene nanoplatelets (GNP) and multiwall carbon nanotube (MWCNT) hybrid nanofillers on the mechanical and thermal properties of reinforced polyethylene terephthalate (PET) have been investigated. The nanocomposites were melt blended using the counter rotating twin screw extruder followed by injection molding. Their morphology, mechanical and thermal properties were characterized. Combination of the two nanofillers in composites formulation supplemented each other which resulted in the overall improvement in adhesion between fillers and matrix. The mechanical properties and thermal stability of the hybrid nanocomposites (PET/GNP1.5/MWCNT1.5) were significantly improved compared to PET/GNP3 and PET/MWCNT3 single filer nanocomposites. However, it was observed that GNP was better in improving the mechanical properties but MWCNT resulted in higher thermal stability of Nanocomposite. The transmission electron microscopy (TEM) and field emission scanning electron microscopy (FESEM) revealed uniform dispersion of the hybrid fillers in PET/GNP1.5/MWCNT1.5 nanocomposites while agglomeration was observed at higher filler content. The MWCNT prevented the phenomenal stacking of the GNPs by forming a bridge between adjacent GNP planes resulting in higher dispersion of fillers. This complimentary geometrical structure is responsible for the significant improvement in the thermal stability and mechanical properties of the hybrid nanocomposites.     

The statistical investigation of mechanical properties of PP/natural fibers composites

A systematic and statistical approach to evaluate and predict the properties of random discontinuous natural fiber reinforced composites. Different composites based on polypropylene and reinforced with natural fibers have been made and their mechanical properties are measured together with the distribution of the fiber size and the fiber diameter. The values obtained have been related to the theoretical predictions, using a combination of the Griffith theory for the effective properties of the natural fibers and the Halpin-Tsai equation for the elastic modulus of the composites. The relationships between experimental results and theoretical predictions are statistically analyzed using a probability density function estimation approach based on neural networks. The results show a more accurate expected value with respect to the traditional statistical function estimation approach. In order to point out the particular features of natural fibers, the same proposed method is also applied to PP-glass fiber composites.     

Effect of Ni-coated short carbon fibers on the mechanical and electrical properties of epoxy composites

Ni-coated short carbon fibers (Ni-SCFs) were prepared using an electrodeposition method. Short carbon fiber (SCF) reinforced epoxy composites were prepared by changing the fiber content (0.1–0.7 wt%). To investigate the effect of Ni-coated short carbon fibers on the mechanical and electrical properties of the composites, we prepared two kinds of reinforcements: the short carbon fibers treated by 400 °C (400 °C treated SCFs) and Ni-SCFs. Fracture characteristics of the composites revealed the Ni coatings and the epoxy matrix had a better interface, so that the results of tensile and bending strength were better in epoxy/Ni-SCFs composites than those in epoxy/400 °C treated SCFs composites. The 400 °C treated SCFs decreased the electrical resistivity of the epoxy composites, compared to the pure epoxy. However the epoxy/Ni-SCFs composites had lower electrical resistivity than epoxy/400 °C treated SCFs with the same fiber content.     

A study of the mechanical properties of natural fibre reinforced composites

This paper presents the results of a current research of the tensile properties: ultimate strength and stiffness modulus in composites using natural reinforcements. Hemp short fibres and pine sawdust were randomly distributed in polypropylene matrices to produce composite plates with 5 mm thickness by injection moulding technique. The specimens were cut from these plates with bone dog shape or plane bars, and tested in tensile and four points bending, respectively. Stiffness modulus and ultimate stresses were obtained for different weight fraction content of reinforcement and discussed taking in account the failure modes. Four series of pine sawdust reinforced specimens were immersed in water in periods up to 20 days. Periodically, the specimens were removed from the water recipient and immediately tested. The damage effect of water immersion time was discussed based in the tensile results and in the water absorption curves.     

Enhancement of the mechanical properties of glass/polyester composites via matrix modification glass/polyester composite siloxane matrix modification

Enhancement of the mechanical and vibrational properties of glass/polyester composites was aimed via matrix modification technique. To achieve this, unsaturated polyester was modified by incorporation of oligomeric siloxane in the concentration range of 1–3 wt%. Modified matrix composites reinforced with woven roving glass fabric were compared with untreated glass/polyester in terms of mechanical and interlaminar properties by conducting tensile, flexure, and short-beam shear tests. It was found that after incorporation of 3 % oligomeric siloxane into the polyester matrix, the tensile, flexural, and interlaminar shear strength (ILSS) values of the resulting composite increased by 16, 15, and 75 %, respectively. The increases in ILSS as well as in tensile and flexural properties were considered to be an indication of better fiber/matrix interaction as confirmed by SEM fractography images. Furthermore, the effect of oligomeric siloxane incorporation on the vibrational properties of the composites was investigated by experimental modal testing and the natural frequencies of the composites were found to increase with increasing siloxane concentration.     

Preparation and properties of alkaline functionalized carbon nanotubes reinforced polyurethane composites

Composites consisting of polyurethane (PU)/carbon nanotubes (CNTs) have been successfully prepared by solution mixing method. CNTs were modified through mechano-chemical reaction to increase the compatibility with PU via hydrogen bondings. SEM microphotographs proved that modified CNTs (M-CNTs) became shorter and FTIR spectra showed that hydroxyl groups had been introduced to the surface of M-CNTs. SEM images of PU/M-CNTs composites also proved that M-CNTs were effectively dispersed in PU matrix. Mechanical property tests showed that addition of M-CNTs could significantly improve the tensile properties of PU/M-CNTs composite (breaking strength enhancement ratio for composite with 5.0 wt% M-CNTs was 103.81 %). The thermal stability of composites with M-CNTs was also improved. The initial degradation temperature enhancement was 19.9 oC for the composite with 0.5 wt% M-CNTs. Electrical property tests showed that the electrical properties were improved by adding M-CNTs. The volume conductivities increased 3 and 5 orders of magnitude for the composites with 5.0 wt% and 10 wt% M-CNTs, respectively. The addition of M-CNTs had little effect on the elastic properties of the composites.     

Characterization of oil palm empty fruit bunch and glass fibre reinforced recycled polypropylene hybrid composites

The effects of hybridization of glass fibre on oil palm empty fruit bunch (EFB) and recycled polypropylene-based composites are described in this paper. The compounding process involved extrusion followed by injection moulding technique to prepare the samples for characterizations. Fibre loading were considered as 40 % of the total weight of the blends and EFB:glass fibre ratio was maintained as 30:70, 50:50, 70:30 and 90:10. Two types of coupling agents of maleic anhydride-grafted polypropylene such as polybond-3200 and fusabond P-613 of different molecular weight and maleic anhydride level were used to improve the interfacial adhesion between the fibres and the matrix. Composites were characterized by density, melt flow index, tensile, Izod impact and flexural testing. Morphological images of the fractured surfaces of the composites were examined by field-emission scanning electron microscopy. Samples were also characterized by thermal tests such as thermogravimetric analysis and differential scanning calorimetry to evaluate the thermal and crystalline properties, respectively. Optimization of hybridization of the fibres and effect of coupling agents were evaluated in terms of various properties of the samples. The composite prepared with EFB:glass fibre ratio of 70:30 showed better reinforcing properties than that of others.     

Bending properties of carbon/glass and carbon/aramid fabric composites with various stacking structures by the VARTM method

In this paper, the bending properties of woven carbon/glass and carbon/aramid fabric-reinforced polymer laminates is studied using a combination of experimental analysis and fracture observation. Six types of each hybrid composite were manufactured by lamination of the carbon/aramid fabric and carbon/glass fabric using VARTM. Bending behaviors were fundamentally evaluated for the six types of monolithic composites laminated by the same fabric. The objective was to achieve a good bending strength by effective combination of composite structures using limited amounts of a raw material. It was shown that the bending property was different, depending on the type of fiber, lamination structure, and the number of layers.     

Effect of temperature and time on mechanical and electrical properties of HDPE/glass fiber composites

In recent years, composites based on glass fiber reinforced polymer have been widely used in order to meet increasing durability and safety regulations, particularly in the power cable, automotive and plane industry. In this paper, mechanical and electrical properties of high density polyethylene (HDPE) and HDPE containing glass fiber polymer composites were investigated and compared at different temperatures. Composite materials were prepared with the hot pressing method. Tensile strength, % elongation and the modulus of elasticity (or Young’s modulus) were determined for each sample at different temperatures. In addition to this, at different temperatures τ _σ and τ _E have mechanical and electrical lifetime respectively, corresponding to mechanical tension (σ) and electrical strength (E), and this was investigated for each sample. As compared to the mechanical and electrical properties of neat HDPE, HDPE/0.5 % glass fiber composites have been found to have better mechanical and electrical durability.     

Mechanical behavior of composites reinforced with fibers caroa

Composites were prepared with 13, 23 30 and 40 % fiber and evaluated the mechanical performance in tensile, flexural and impact. The mechanical properties of these composites were also evaluated function of time at 110 °C thermal exposure. Caroa fibers were characterized by techniques such as thermal gravimetric analysis (TGA), X-ray diffraction (XRD) and scanning electron microscopy (SEM). It was found that the best mechanical properties were achieved for composites containing 23 to 30 % fiber. The incorporation of 23 % fiber caroa increased both the modulus of elasticity in the tensile test as the flexural strength and impact, the composite with 30 % fiber caroa showed higher tensile strength. The results show that the tensile and flexural strength of the composite decreased with time of thermal exposure. The thermal aging at 110 °C caused a decrease in tensile properties of the composites.     

Role of potassium permanganate and urea on the improvement of the mechanical properties of jute polypropylene composites

Jute fabrics (hessian cloth) reinforced polypropylene (PP) matrix composites (45 wt% fiber) were fabricated by compression molding. Jute fabrics were treated with 2-hydroxyethyl methacrylate (HEMA) using ultraviolet radiation in order to improve the mechanical properties of the composites. Concentration of HEMA, soaking time and radiation dose were optimized. It was found that 15% HEMA in methanol along with photoinitiator Darocur-1173 (2 %), 10 min soaking time and 20th pass of radiation rendered better performance. Urea of different concentrations (0.5–2 %) was incorporated with 15 % HEMA to monitor its effect on the properties and 1 % urea revealed the best results. For the improvement of the properties, jute fabrics were treated with potassium permanganate (KMnO₄) solution in acetone of different concentrations (0.02, 0.03, 0.05, and 0.5 %) at different soaking times (1, 2, 3, and 5 min) before the composite fabrication. Optimized jute fabrics (jute fabrics treated with 0.03 % KMnO₄) were again treated with HEMA (15 %) solution along with urea (1 %) and promising improvement of mechanical properties of the composites was observed. Scanning electron microscopy, water uptake, soil degradation and thermal aging of the treated and untreated composites were also performed.     

Tensile response and fracture and failure behavior of jute fabrics-flyash-vinylester hybrid composites

In this work, hybrid materials consisting on a vinylester matrix simultaneaously reinforced with jute woven fabrics and flyash particles were prepared. The tensile response and the fracture and failure behavior of these hybrid composites were investigated. Thermal stability of these materials was also studied. The aim was to obtain an environmentally friendly hybrid material with a good balance of tensile and fracture properties at relatively low cost. The effect of a novel treatment for the jute fabrics on the hybrids mechanical and fracture properties was investigated. The best balance of tensile and fracture properties was obtained for the hybrid consisting of fabrics treated with alkali under stress and fly ashes which also exhibited relatively high thermal stability.     

Compressional behavior of carbon nanotube reinforced mesophase pitch-based carbon fibers

The tensile-recoil compressional behavior of the carbon nanotube reinforced mesophase pitch (MP)-based composite carbon fibers (CNT-re-MP CFs) was investigated by using Instron and SEM. The CNT-re-MP CFs exhibited improved, or at least equivalent, compressive strength as compared with commercial MP-based carbon fibers. Particularly, when CNT of 0.1 wt% was reinforced, the ratios of recoil compressive strengths to tensile strength of CNT-re-MPCFs were much higher (the difference is at least 10% or higher) than those for the commercial counterparts and even than those for PAN-based commercial carbon fibers. FESEM micrographs showed somewhat different fractography from that of a typical shear failure as the CNT content increased.     

Bio-composites: Development and mechanical characterization of banana/sisal fibre reinforced poly lactic acid (PLA) hybrid composites

The work focuses on the influencing effect of fiber surface treatment by BP towards mechanical properties of BSF reinforced PLA composites. BSF were treated by BP to improve the adhesion between fibres and matrix. BSF (30 wt %) reinforced PLA (70 wt %) hybrid composites were fabricated by means of twin screw extrusion followed by injection molding process. Tensile strength, flexural strength and modulus were tested by means of UTM. The morphological analysis of the untreated and treated BSF reinforced PLA composites in comparison with virgin PLA was carried out by SEM to examine the existence of interfacial adhesion between BSF and PLA. The resultant data reveals that treated BSF restricts the motion of the PLA matrix due to better wettability and bonding. Consequently, mechanical properties like tensile and flexural moduli of BSF reinforced PLA composites were enhanced in comparison to virgin PLA and untreated BSF reinforced PLA composites. The results are discussed in detail.