Mechanical properties of uniaxial natural fabric Grewia tilifolia reinforced epoxy based composites: Effects of chemical treatment

The effects of chemical treatment on the mechanical, morphological, and chemical resistance properties of uniaxial natural fabrics, Grewia tilifolia/epoxy composites, were studied. In order to enhance the interfacial bonding between the epoxy matrix and the Grewia tilifolia fabrics, two different types of treatment: alkali treatment (5 % NaOH) and (3-aminopropyl)-triethoxysilane coupling agent (CA), were used. The epoxy composites containing 0–15 wt% of Grewia tilifolia fabric were prepared by hand lay-up technique, at room temperature. The tensile and flexural properties of the untreated, alkali-treated and coupling agent treated Grewia tilifolia reinforced epoxy composites were determined as a function of fabric loading. The 9 % wt Grewia tilifolia fabric reinforced epoxy composites showed improved tensile and flexural modulii when compared to the neat epoxy matrix. Significant improvement in the mechanical properties was obtained when both alkali and coupling agent treated fabrics were used as reinforcement. Morphological studies demonstrated that better adhesion between the fabrics and the matrix was achieved especially when the alkali-treated and coupling agent treated Grewia tilifolia fabrics were used in the composites. For the water absorption and chemical resistance studies, various solvents, acids and alkalis were used on the epoxy composites. This study has shown that Grewia tilifolia fabric/epoxy composites are promising candidates for structural applications, where high strength and stiffness are required.     

Impact of succinic anhydride on the properties of jute fiber/polypropylene biocomposites

Chemical treatment is an often-followed route to improve the physical and mechanical properties of natural fiber reinforced polymer matrix composites. In this study, the effect of chemical treatment on physical and mechanical properties of jute fiber reinforced polypropylene (PP) biocomposites with different fiber loading (5, 10, 15, and 20 wt%) were investigated. Before being manufactured jute fiber/PP composite, raw jute fiber was chemically treated with succinic anhydride for the chemical reaction with cellulose hydroxyl group of fiber and to increase adhesion and compatibility to the polymer matrix. Jute fiber/PP composites were fabricated using high voltage hot compression technique. Fourier Transform Infrared spectroscopy (FTIR) and Scanning Electron Microscopy (SEM) tests were employed to evaluate the morphological properties of composite. Succinic anhydride underwent a chemical reaction with raw jute fiber which was confirmed through FTIR results. SEM micrographs of the fractured surface area were taken to study the fiber/matrix interface adhesion and compatibility. Reduced fiber agglomeration and improved interfacial bonding was observed under SEM in the case of treated jute fiber/PP composites. The mechanical properties of jute/PP composite in terms of Tensile strength and Young’s modulus was found to be increased with fiber loading up to 15 wt% and decreased at 20 wt%. Conversely, flexural strength and flexural modulus increased with fiber loading up to 10 wt% and start decreasing at 15 wt%. The treated jute/PP composite samples had higher hardness (Rockwell) and lower water absorption value compared to that of the untreated ones.     

Effect of coir fiber content and compatibilizer on the properties of unidirectional coir fiber/polypropylene composites

The main objective of this research was to study the effect of fiber content variation and stearic acid (SA) treatment on the fundamental properties of unidirectional coir fiber (CF) reinforced polypropylene (PP) composites. Several percentages of filler contents were used (10–40 wt %) in order to gain insights into the effect of filler content on the properties of the composites. Coir/PP composites were fabricated by compression molding, and the properties of composites were studied by physico-mechanical and thermal properties. The results from mechanical properties such as tensile strength (TS), tensile modulus (TM) and impact strength (IS) of the CF/PP composites were found to be increased with increasing fiber content, reached an optimum and thereafter decreased with further increase in fiber content. Treatment of the coir with SA as the coupling agent enhanced the mechanical properties, crystallization temperature and crystallinity of virgin PP and water desorption of the resulting composites, resulting from the improved adhesion between the CF and PP matrix. Scanning electron micrographs (SEM) of the tensile fractured samples showed improved adhesion between fiber and matrix upon treatment with SA. Interfacial shear strength (IFSS) of the composites was measured by single fiber fragmentation test (SFFT).     

Development of mathematical models and estimation for the mechanical properties of organic fiber reinforced polyester composites

Organic fiber from animal waste was used for the development of environmentally friendly animal fiber based polyester composites using cow hair. The cow hair fibers were cut into 10 mm lengths to produce the needed short fiber for random dispersion in the matrix. Before use, some of the fibers were treated with sodium hydroxide for fiber surface modification while some were left as untreated. Composites were developed using predetermined proportions of the fibers in an open mould production process. Samples were formed into tensile and flexural shape in their respective moulds and were stripped off the moulds after curing while further curing was ensured for 27 days before testing. Tensile and flexural properties of the cow hair fiber reinforced polyester composites were evaluated from which it was discovered that the untreated fiber reinforced composites possess better enhancement of mechanical properties compared to the treated fiber reinforced composites and the unreinforced polyester material. Mathematical models for the tensile and flexural properties were developed using statistical packages and estimation using developed software. The developed models revealed high degree of correlation between the experimental values and the predicted values. This denotes that the models can be used to predict the mechanical properties of cow hair reinforced polyester composites for various reinforcement contents.     

Flexural and impact properties of chemically treated sugar palm fiber reinforced high impact polystyrene composites

The effects of chemical treatment on the flexural and impact properties of sugar palm fiber reinforced high impact polystyrene (HIPS) composites were studied. Two types of concentration of alkali solution (4 % and 6 %) and also two types of percentage of compatibilizing agent (2 % and 3 %) have been used in this study. The alkaline treatment is carried out by immersing the fibers in 4 % and 6 % of alkali solution for 1 hour. A 40 wt. % of alkali treated sugar palm fiber (SPF) was blended with HIPS using Brabender machine at temperature of 165 °C. The second treatment was employed by compounding mixture of sugar palm fibers and HIPS with 2 and 3 % of compatibilizing agent using the same procedure. The composites plate with dimensions of 150×150×3 mm was produced by using the hot press machine. The flexural strength, flexural modulus and impact strength of composites were measured and the values were compared to the untreated composites. Improvement of the mechanical properties of the composites has been shown successfully. Alkali treatment using 6 % NaOH solution improve the flexural strength, flexural modulus and impact strength of the composites as amount 12 %, 19 % and 34 % respectively, whereas compatibilizing agent treatment only showed the improvement on the impact strength, i.e. 6 % and 16 % improvement for 2 % and 3 % MAH respectively.     

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.     

Effects of surface treatment of ramie fibers in a ramie/poly(lactic acid) composite

The chemical and morphological properties of ramie fibers treated by chemical surface modification were examined with Fourier transform infrared (FT-IR) spectroscopy. The mechanical and thermal decomposition properties were evaluated with respect to tensile strength, tensile modulus and thermogravimetric analysis (TGA). Surface morphological changes were investigated with scanning electron microscopy (SEM). Finally, the capabilities of composites reinforced with various chemically treated fibers were analyzed by investigating tensile and impact strengths. Additionally, the thermal mechanical properties of the composites were investigated with thermal mechanical analysis (TMA). Based on the results of these analyses, we concluded that pectin, lignin and hemicellulose were removed and thermal stability was increased with chemical treatments. The composites reinforced with ramie fiber showed better properties compared with pure PLA matrix with respect to tensile and impact strengths. The peroxide-treated fiber composite had the smallest thermal expansion.     

Nano-SiO2 filled rice husk/polypropylene composites: Physico-mechanical properties

In this research, reinforcing effect of hybrid filler including rice husk (RH), beech bark (BB) and nano-SiO₂, in polypropylene has been investigated. In the sample preparation, four levels of filler loading were used for waste lignocellulosic materials (55-58 wt.%) and nano-SiO₂ (0-4 wt.%). In order to increase the interphase adhesion, polypropylene grafted with maleic anhydride was added as a coupling agent to all the composites studied. The physical properties, viz. the thickness swelling and water absorption, and mechanical properties, namely, the tensile, flexural and notched Izod impact strengths, of the composites were determined. Generally, high amount of filler content in composites can lead to the reduction of interfacial adhesion between matrix polymer and filler, and it limits their applications. The results showed that while flexural properties and elongation at break were moderately improved by the increase in the amount of filler in the matrix, tensile and Izod impact strengths decreased dramatically. However, the composites had acceptable mechanical strength levels. The mechanical properties of composites filled with RH are generally greater than BB composites. The thickness swelling and water absorption of the composites increased with the increase in the filler loading, but to a negligible extent as compared with the wood-based composites and the solid woods. Nano-SiO₂ addition showed little positive effect on the mechanical properties. It can be concluded from this study that the used waste lignocellulosic materials are attractive reinforcements from the standpoint of their physico-mechanical properties.     

Mechanical properties of denim fabric reinforced poly(lactic acid)

Denim, a twilled cotton fabric, was used to enhance the mechanical and thermal properties of poly(lactic acid) (PLA). The denim fabric reinforced composites with different numbers of denim layers were fabricated by using a hand layup method. The impact, tensile, and dynamic mechanical properties of the composites were observed with increasing denim layers to examine the reinforcing effect of denim fabrics. Numerical analysis was carried out to model the elastic modulus of the composite by using a commercial software. Three-dimensional geometry of the denim fabric reinforced PLA composite was generated through a CAD program, and the elastic modulus was calculated by applying uniform deformation on one surface. The impact strength, tensile strength, and thermal properties of the composites were improved by piling denim fabrics. The denim fabric reinforced composites exhibited outstanding impact strength due to the retarded crack propagation as well as large energy dissipation. The 3 layer denim reinforced composite showed best results among all specimens, and its impact strength, tensile strength, and tensile modulus were measured to be 82 J/m, 75.76 MPa, and 4.65 GPa, respectively. The PLA/denim composites have good mechanical properties and can substitute traditional composites such as glass fiber or carbon fiber reinforced composites.     

The effect of gelation and curing temperatures on mechanical properties of pultruded kenaf fibre reinforced vinyl ester composites

Process parameters such as gelation and curing temperatures are parameters that influence the pultruded kenaf reinforced vinyl ester composites profile quality and performance. The effect of gelation and curing temperatures on mechanical (tensile, flexural and compression properties) and morphological properties of pultruded kenaf reinforced vinyl ester composites were analyzed. Obtained results indicated that increase of gelation and curing temperatures during the pultrusion process of kenaf reinforced vinyl ester composites influenced the mechanical properties of the composites. When the gelation and curing temperatures were increased, tensile strength, tensile modulus, flexural strength, flexural modulus and compressive strength were affected and they were either increased or decreased. The factors that influenced these results include improper curing, excessive curing, water diffusion, and the problems associated with interfacial bonding between fibre and matrices. The optimum values of the tensile strength for gelation and curing temperatures of kenaf pultruded composites were at 100 °C and 140 °C, tensile modulus at 80 °C and 180 °C, flexural strength at 100 ° and 140 °, flexural modulus at 120 ° and 180 °, and compressive strength at 120 °C and 180 °C, respectively. The scanning electron micrographs of tensile fractured samples clearly show that with the increase in gelation temperature, it creates the lumens between matrix and kenaf fibre thus reducing tensile properties whereas increasing the curing temperature caused less fibre pull out and enhanced fibre/matrix interfacial bonding.     

Effect of the low and radio frequency oxygen plasma treatment of jute fiber on mechanical properties of jute fiber/polyester composite

We investigated the surface modification of jute fiber by oxygen plasma treatments. Jute fibers were treated in different plasma reactors (radio frequency “RF” and low frequency “LF” plasma reactors) using O₂ for different plasma powers to increase the interface adhesion between jute fiber and polyester matrix. The influence of various plasma reactors on mechanical properties of jute fiber-reinforced polyester composites was reported. Tensile, flexure, short beam shear tests were used to determine the mechanical properties of the composites. The interlaminar shear strength increased from 11.5 MPa for the untreated jute fiber/polyester composite to 19.8 and 26.3 MPa for LF and RF oxygen plasma treated jute fiber/polyester composites, respectively. O₂ plasma treatment also improved the tensile and flexural strengths of jute fiber/ polyester composites for both plasma systems. It is clear that O₂ plasma treatment of jute fibers by using RF plasma system instead of using LF plasma system brings about greater improvement on the mechanical properties of jute/polyester composites.     

Evaluating the Mechanical Behavior of Basalt Fibers/Epoxy Composites Containing Surface-modified CaCO<Subscript>3</Subscript> Nanoparticles

Polymer matrix composites (PMCs) owing to their outstanding properties such as high strength, low weight, high thermal stability and chemical resistance are broadly utilized in various industries. In the present work, the influence of silanized CaCO₃ (S-CaCO₃) with 3-aminopropyltrimethoxysilane (3-APTMS) coupling agent at different values (0, 1, 3 and 5 wt.% with respect to the matrix) on the mechanical behavior of basalt fibers (BF)/epoxy composites was examined. BF-reinforced composites were fabricated via hand lay-up technique. Experimental results from three-point bending and tensile tests showed that with the dispersion of 3 wt.% S-CaCO₃, flexural strength, flexural modulus, tensile strength and tensile modulus enhanced by 28 %, 35 %, 20 % and 30 %, respectively. Microscopic examinations revealed that the development of the mechanical properties of fibrous composites with the incorporation of modified CaCO₃ was related to enhancement in the load transfer between the nanocomposite matrix and BF as well as enhanced mechanical properties of the matrix part.     

Mechanical and thermal properties of recycled poly(ethylene terephthalate) reinforced newspaper fiber composites

This study presents the mechanical and thermal properties of environment-friendly composites made from recycled newspaper fibers reinforced recycled poly(ethylene terephthalate) (rPET) resin with the addition of styrene-ethylene-butylene-styrene grafted maleic anhydride (SEBS-g-MA) as compatibilizer. The effect of SEBS-g-MA addition (i.e., 10 phr) by using a twin-screw extruder to the rPET resin, followed by different fiber content (5, 10 and 15 wt.%) on the tensile, flexural and impact properties of the composites were determined. Stiffness of composites increased significantly compared to those of rPET/SEBS-g-MA blend. Fiber addition resulted in moderate increases in both tensile and flexural strength of the composites. Scanning electron microscope (SEM) photomicrographs of the impact fracture surfaces demonstrate good adhesion at 5 and 10 % fiber content. Differential scanning calorimetry (DSC) showed that the presence of newspaper fibers enhanced the nonisothermal crystallization kinetics and crystallinity. Thermal stability of the composites was improved as indicated by thermogravimetric analysis (TGA).     

Effect of pineapple leaf fibre and kenaf fibre treatment on mechanical performance of phenolic hybrid composites

In this work, hybrid composites were fabricated by hand layup method to hybridize treated Pineapple leaf fibre (PALF) and kenaf fibre (KF) in order to achieve superior mechanical properties on untreated hybrid composites. Silane treated PALF/KF phenolic hybrid composites were prepared on various fibre fraction to investigate mechanical properties and compared with untreated PALF/KF phenolic hybrid composites. The effects of silane treatment on hybrid composites were investigated by fourier transform infrared spectroscopy (FTIR) and found very effective peaks. Effects of treated hybrid composites were morphologically investigated by using scanning electron microscopy images and analysed the tensile results. Treated PALF/KF phenolic hybrid composites enhanced the flexural strength, modulus, impact strength and energy absorption while tensile strength and modulus decreased. The overall performances of 70 % PALF 30 % Kenaf hybrid composites were improved after silane treatment. Silane treatment of fibres improved the mechanical performance of hybrid composites and it can be utilized to produce components for building structure, materials and automobile applications.     

Coir fiber reinforced polypropylene composite panel for automotive interior applications

In this study, physical, mechanical, and flammability properties of coconut fiber reinforced polypropylene (PP) composite panels were evaluated. Four levels of the coir fiber content (40, 50, 60, and 70 % based on the composition by weight) were mixed with the PP powder and a coupling agent, 3 wt % maleic anhydride grafted PP (MAPP) powder. The water resistance and the internal bond strength of the composites were negatively influenced by increasing coir fiber content. However, the flexural strength, the tensile strength, and the hardness of the composites improved with increasing the coir fiber content up to 60 wt %. The flame retardancy of the composites improved with increasing coir fiber content. The results suggest that an optimal composite panel formulation for automotive interior applications is a mixture of 60 wt % coir fiber, 37 wt % PP powder, and 3 wt % MAPP.     

Compatibilizing effects of polypropylene-g-itaconic acid on the polypropylene composites

We prepared long carbon fiber (LCF)-reinforced thermoplastic composites using a compatibilizer of itaconic acid grafted polypropylene (PP-g-IA). We confirmed the structure of PP-g-IA and investigated the compatibilizing effects of PPg- IA on LCF/polypropylene composites. The tensile strength, tensile moduli, flexural strength, and flexural moduli of the composites increased with increasing PP-g-IA content in the thermoplastic composites. Using single pull-out analyzing system, we found PP-g-IA improved interfacial strength between the carbon fiber and PP matrix. The thermal properties of the composites were measured by thermogravimetric analysis (TGA). We could observe that LCF enhanced the mechanical properties and thermal decomposition temperature of the polypropylene (PP) composites, compared with neat PP. The fractured surfaces of PP/PP-g-IA/LCF composites showed that PP-g-IA was effective for improving the interfacial adhesion between LCF and PP matrix.     

Jute yarn as reinforcement for polypropylene based commingled eco-composites: Effect of fibre content and chemical modifications on accelerated ageing and tear properties

Bidirectional PP/jute yarn eco-composites were fabricated via environment friendly commingling technique and its long term durability/life time was monitored as an effect of accelerated solar ageing on its mechanical properties (tensile & flexural). Accelerated solar ageing promoted the thermal oxidation of PP thus resulting in deterioration of its properties, however; MAPP and KMnO₄ treated commingled composites showed much better stability towards thermal oxidation brought about by the solar concentrator, compared to untreated sample and neat polypropylene. This increased resistivity of treated composites (especially MAPP and KMnO₄) towards thermal oxidation brought about by the solar concentrator is due to the increased interfacial adhesion between the matrix and jute yarn owing to chemical modifications. The significance of effective stress transfer between the PP matrix and reinforcing jute yarns is evident from the increased tear resistance of PP/jute yarn commingled composites with increasing fibre content and also with different chemical treatments.     

Some of the mechanical and thermal properties of wheat straw filled-PP composites

The objective of this investigation was to evaluate the mechanical, thermal stability and viscoelastic behaviors of experimental PP composites made from wheat straw and PP-g-MA coupling agent. Four levels of wheat straw, 10, 20, 25 and 30 wt % and two levels of coupling agent, 0 and 3 % wt were mixed with PP in rotary type mixer and injection molding process, respectively. Tensile characteristics and impact strength, thermal gravity and dynamic mechanical and thermal analysis of the samples were evaluated. Based on the results, it was observed that the tensile properties increased and impact strength decreased with the increase in the fiber loading from 10 % to 30 %. Further, the composites treated with PP-g-MA exhibited improved mechanical properties which confirmed efficient fiber-matrix adhesion. DMT analysis showed that the PP composites made of 30 % wheat straw containing 3 % PP-g-MA showed the highest E’ and lowest tan δ than the untreated ones. Also, the thermal stability of wheat straw was lower than PP and as filler content in the composites increased, the thermal stability decreased and the ash content increased.     

Matrix modification with silane coupling agent for carbon fiber reinforced epoxy composites

To improve interfacial adhesion between carbon fiber and epoxy resin, the epoxy matrix is modified with N-(2-aminoethyl)-3-aminopropylmethyldimethoxysilane (YDH602) and N-(2-aminoethyl)-3-aminopropyltrimethoxysilane (YDH792), respectively. And the effect of matrix modification on the mechanical performance of carbon/epoxy composites is investigated in terms of tensile, flexural and interlaminar properties. The flexural properties indicate that the optimum concentration of silane coupling agents YDH602 and YDH792 for the matrix modification is approximately 0.5 wt% of the epoxy resin system, and the mechanical properties of the YDH792-modified epoxy composites is better than that of the YDH602-modified epoxy composites at the same concentration. Compared to unmodified epoxy composite, the incorporation of 0.5 wt% YDH792 results in an increase of 4, 44 and 42 % in tensile, flexural and interlaminar shear strength (ILSS) values of the carbon/epoxy composite, respectively, while the corresponding enhancement of tensile and flexural modulus is 3 and 15 %. These improvements in mechanical properties can be considered to be an indication of better fiber/matrix interfacial adhesion as confirmed by SEM micrographs of the fracture surface after interlaminar shear testing. The viscosity of the modified epoxy resin system can be reduced by incorporation of silane coupling agent YDH792, which is beneficial for fiber impregnation or wetting during liquid composite molding process.     

Flexural characteristics of coir fiber reinforced cementitious composites

This study has examined the flexural properties of natural and chemically modified coir fiber reinforced cementitious composites (CFRCC). Coir fibers of two different average lengths were used, and the longer coir fibers were also treated with a 1 % NaOH solution for comparison. The fibers were combined with cementitious materials and chemical agents (dispersant, defoamer or wetting agent) to form CFRCC. The flexural properties of the composites, including elastic stress, flexural strength, toughness and toughness index, were measured. The effects of fiber treatments, addition of chemical agents and accelerated ageing of composites on the composites’ flexural properties were examined. The results showed that the CFRCC samples were 5–12 % lighter than the conventional mortar, and that the addition of coir fibers improved the flexural strength of the CFRCC materials. Toughness and toughness index, which were associated with the work of fracture, were increased more than ten times. For the alkalized long coir fiber composites, a higher immediate and long-term toughness index was achieved. SEM microstructure images revealed improved physicochemical bonding in the treated CFRCC.