Coir-polyester Composites Research Articles

Influence of fibre loading and surface treatment on the impact strength of coir polyester composites

Purpose: In this work, coir fibre with varying fibre content was selected as reinforcements to prepare polymer-based matrices and the problem of reduced fibre-matrix interfacial bond strength has been diluted by chemical treatment of coir fibres with alkali solution. Design/methodology/approach: The effect of fibre loading, solution concentration and soaking time on the impact strength of the composites were analyzed using statistical techniques. Response Surface Methodology (RSM) approach was used to model and optimize the impact properties of coir-polyester composites. Findings: The impact strength of coir fibre reinforced polyester composite depends mainly on the fabrication parameters such as fibre-polyester content, soaking time, concentration of soaking agent and adhesive interaction between the fibre and reinforcement. Research limitations/implications: The mechanical properties of any coir polyester composite depend on the nature bonding between the fibre and reinforcement. The presence of cellulose, lignin on the periphery of any natural fibre reduces the bonding strength of the composite. This limitation is overcome by fibre treatment over sodium hydroxide to have better impact properties. Practical implications: Now days, natural fibre reinforced composites are capable of replacing automotive parts, subjected to static loads such as engine Guard, light doom, name plate, tool box and front panels etc. These materials can withstand any static load due to its higher strength to weight ratios. Originality/value: The effect of fibre loading, solution concentration and soaking time on the impact strength of the composites were analyzed using statistical techniques. Response Surface Methodology (RSM) approach was used to model and optimize the impact properties of coir-polyester composites. The impact strength of NaOH impregnated coir fibre reinforced polyester composites was evaluated.

Effects of sodium carbonate on the performance of epoxy and polyester coir-reinforced composites

Surface modification induced by sodium carbonate on coir fibres was studied in view of its application as a reinforcing agent in polyester and epoxy polymer fibre-reinforced composites. Coir fibres were treated with a 10 wt% sodium carbonate solution for different periods of time (24, 96 and 168 h) at room temperature. The surface treatment was evaluated by scanning electron microscopy, X-ray diffraction and thermogravimetric analysis. Tensile, flexural and impact properties of treated and untreated coir fibre-reinforced composites were compared. Coir-reinforced epoxy and polyester composites were manufactured by the uniform dispersion of randomly oriented coir fibres within the polymeric matrix. Tensile and flexural modulus of coir-reinforced polyester composites increased nearly 28% and 25%, respectively after 96 h of coir treatment. An analogous increase of 31% and 17% was obtained for coir-reinforced epoxy composites. In addition, coir-polyester composites achieved superior tensile (∼17%) and flexural (∼5%) modulus and impact strength (∼193%) compared with coir-epoxy-derived composites. In contrast, coir-epoxy composites led to superior tensile and flexural strength. The experimental results revealed that sodium carbonate solution effectively removes hemicellulosic compounds, promotes swelling and increases superficial roughness of the fibres, improving the mechanical properties (modulus and strength) of the coir-reinforced composites studied.

Effect of Coconut Shell Powder as Filler on the Mechanical Properties of Coir-polyester Composites

Coir mat was used as reinforcement, polyester resin was used as matrix and coconut shell powder (CSP) was used as filler material which was employed as 10, 20, 30, 40, 50, 60 and 100% by weight in the composites. Coir mat/polyester resin composites were made by hand lay-up technique. Mechanical properties such as tensile strength (TS), bending strength (BS), tensile modulus (TM), bending modulus (BM), elongation at break and impact strength (IS) were also investigated. The maximum increase of TS, BS, TM, BM and IS were found to be 44.44, 128.00, 17.96, 112.09 and 62.50% respectively for 30% filler content on the composites. It was revealed that the strength properties of the composites were increased with the increase in filler content up to 30% by weight, however, further increase in filler content the value decreased. Gamma radiation of 100, 250 and 300 krad doses were applied on 30, 40 and 60% filler content composites. Gamma radiation dose of 250 krad showed better result than that of other doses. IS of the composites improved 48.08, 26.67 and 17.50% for 30, 40 and 60% filler content respectively at 250 krad, where 30% filler content composites displayed the highest improvement. Degradation tests of the composites for up to 50 days were performed in a soil medium. It was revealed that BS decreased for all the composites.

A Study on Impact Strength Characteristics of Coir Polyester Composites

To study the energy absorption capability of coir polyester composites, experimental studies were conducted as per ASTM D256 norms. Experiments were conducted on specimens with both untreated and treated with 5% NaOH solutions. The specimens of 2 mm, 3 mm, 4 mm, 5 mm and 6 mm thicknesses with fiber volume fraction of 10%, 15%, 20%, 25% and 30% were tested to study the variation of their impact strength with variation in specimen thickness and fiber volume fraction respectively. From the results it is observed that, as the thickness and fiber volume fraction of both treated and untreated coir polyester composite specimens increases, the impact strength also increases. Untreated coir polyester composite of 30% fiber volume fraction yielded its highest impact strength of 1.570 N-m. Similarly treated composite specimens also yielded its peak impact strength of 1.275 N-m at its 30% fiber volume fraction.

Statistical Analysis and Particle Swarm Based Optimization of Mechanical Properties of Rice Husk and Termite Mound Soil Impregnated Coir–Polyester Composites

The tensile, flexural and impact properties of rice husk and termite mound soil particle impregnated coir fiber–polyester composites were evaluated in order to introduce a new variety of bio particulated natural fiber–polymer composites. In this investigation the problem of matrix cracking which causes quick failure of natural fiber reinforced polymer composites was solved by matrix strengthening using inclusion of bio particulates. The interlaminar bond between constituents of composites was studied using SEM images. The effects of fiber length, particulate content and fiber content on mechanical properties of rice husk and termite mound soil impregnated coir–polyester composites were analyzed using correlation and regression analysis procedures. The statistical interference techniques namely Weibull distribution was used to validate the mechanical properties of the composites. The optimum fabrication parameters for better mechanical properties were envisaged using particle swarm optimization.

A lexicographic multiobjective genetic algorithm for optimization of mechanical properties of crab carapace impregnated coir–polyester composites

This work is aimed at determining the possibility of using crab carapace materials as reinforcing fillers in the coir fiber reinforced polyester composite. The sample preparation was carried out with three levels of fiber length (10, 30, & 50 mm), fiber weight content (10, 25, and 40%), and additive weight content (2, 4, and 6%). The composite sheets were prepared by impregnating crab carapace additive obtained from crab shell with coir fiber reinforced polyester composite using compression molding machine. The tensile, flexural, and impact strength of the composites were determined as per ASTM standards and regression models were developed to predict the mechanical behaviors of the composites using statistical technique. The fabrication parameters considered in this investigation has significantly contributed toward the mechanical properties of the composites. The developed regression models were optimized to obtain the maximum values of mechanical properties using single objective genetic algorithm and multiobjective lexicographic method in this investigation. POLYM. COMPOS., 37:844–853, 2016. © 2014 Society of Plastics Engineers

Mechanical and machinability behaviors of woven coir fiber-reinforced polyester composite

The research on coir-polyester composites initiated the interest in the development of woven coir fiber-reinforced polyester composites. The mechanical properties of woven coir-polyester composites were evaluated as per ASTM standards and the machinability behavior was studied by conducting drilling tests in this investigation. The woven coir-polyester composites exhibited the average values of tensile, flexural and impact strength of 19.9 MPa, 31.3 MPa and 49.9 kJ/m2 respectively. The effect of NaOH treatment on the improvement of mechanical properties of woven coir-polyester composites were studied in this investigation. The 40 % increase of tensile strength, 42 % increase of flexural strength and 20 % increase of impact strength were achieved by treated woven coir fiber-reinforced polyester composites. The regression models for predicting thrust force, torque and tool wear in drilling of woven coir-polyester composites were developed and the effect of drilling parameters were analyzed.

Effect of soaking time and concentration of NaOH solution on mechanical properties of coir–polyester composites

The green husk coir fibres were treated with different levels of soaking time and concentration of alkali solution. As a result of alkali treatment, the surface modifications were done on the fibre surface and were studied using scanning electron micrographs. The coir–polyester composites were fabricated using hand lay up process and the mechanical properties (tensile, flexural and impact strength) were evaluated as per ASTM standards. The effect of soaking time and concentration of NaOH solution were studied based on evaluated values of mechanical properties to find out optimum fibre treatment parameters.

Drilling analysis of coir-fibre-reinforced polyester composites

An investigation has been carried out to make use of coir, a natural fibre abundantly available in India. Coir-polyester composites were prepared and their mechanical and machinability characteristics were studied. The short coir-fibre-reinforced composites exhibited the tensile, flexural and impact strength of 16·1709 MPa, 29·2611 MPa and 46·1740 J/m, respectively. The regression equations were developed and optimized for studying drilling characteristics of coir-polyester composites using the Taguchi approach. A drill bit diameter of 6 mm, spindle speed of 600 rpm and feed rate of 0·3 mm/rev gave the minimum value of thrust force, torque and tool wear in drilling analysis.

Mechanical behaviours of calcium carbonate-impregnated short coir fibre-reinforced polyester composites

The tensile, flexural, and impact behaviours of calcium carbonate-impregnated coir fibre-reinforced polyester composites were evaluated. The short untreated coir fibres with different proportions of length, diameter, and filler content were used as reinforcements in polymer-based matrices. The fabricated composites with different levels of fibre parameters were tested as per ASTM standards. The mathematical models of mechanical behaviours were developed using statistical package. The effects of calcium carbonate on the mechanical properties of coir–polyester composites and prediction of mechanical properties using regression models were investigated.

The influence of fiber surface modification on the mechanical properties of coir‐polyester composites

AbstractCoir, an important lignocellulosic fiber, can be incorporated in polymers like unsaturated polyester in different ways for achieving desired properties and texture. But its high level of moisture absorption, poor wettability and insufficient adhesion between untreated fiber and the polymer matrix lead to debonding with age. In order to improve the above qualities, adequate surface modification is required. In our present work, fiber surface modification was effected through dewaxing, alkali (5%) treatment, aqueous graft copolymerization of methyl methacrylate (MMA) onto 5% alkali treated coir for different extents using CuSO4 – NaIO4 combination as an initiator system and cyanoexhylation with a view to improve the mechanical performance of coir‐polyester composites. Mechanical properties like tensile strength (PS), flexural strength (ES) and impact strength (IS) of the composites as a function of fiber loading and fiber surface modification have been evaluated. Composites containing z5 wt% of fiber (untreated) improved tensile and flexural strength by 30% and 27% respectively in comparison to neat polyester. The work of fracture (impact strength) of the composite with 25 wt% fiber content was found to be 967 J/m. The elongation at break of the composites exhibits an increase with the introduction of fiber, All types of surface modification result In improved mechanical properties of the composites. Significant improvement in mechanical strength was also observed for composites prepared from 5% PMMA grafted fiber.

The influence of fibre treatment on the performance of coir-polyester composites

Surface modifications of coir fibres involving alkali treatment, bleaching, and vinyl grafting are made in view of their use as reinforcing agents in general-purpose polyester resin matrix. The mechanical properties of composites like tensile, flexural and impact strength increase as a result of surface modification. Among all modifications, bleached (65°C) coir-polyester composites show better flexural strength (61.6 MPa) whereas 2% alkali-treated coir/polyester composites show significant improvement in tensile strength (26.80 MPa). Hybrid composites comprising glass fibre mat (7 wt.%), coir fibre mat (13 wt.%) and polyester resin matrix are prepared. Hybrid composites containing surface modified coir fibres show significant improvement in flexural strength. Water absorption studies of coir/polyester and hybrid composites show significant reduction in water absorption due to surface modifications of coir fibres. Scanning electron microscopy (SEM) investigations show that surface modifications improve the fibre/matrix adhesion.

Coir-Glass Intermingled Fibre Hybrid Composites

The aim of the investigation is to evaluate the enhancement in the proper ties of coir-polyester composites by incorporating glass as intimate mix with coir. Addi tion of relatively small volume fraction (0.05) of glass enhances the tensile strength by about 100%, flexural strength by more than 50 % and impact strength by more than 100 % . Coir-glass intermingled hybrid composites (CGP) absorb moisture 4 to 5 times less than that of coir-polyester composite (CRP) on immersing in boiling water for 2 hrs and the former thereby shows considerably better resistance to weathering. It has also been ob served that CGP core-GRP shell laminates possess better flexural and interlaminar shear strength compared to that of CRP core-GRP shell laminates containing equivalent volume fractions of the fibres as in the former.

Alkali treatment of coir fibres for coir-polyester composites

Coir fibres were subjected to alkali treatment with a view to improving the wettability of coir fibres by a commercially available resin such as polyester. Tensile strength of the fibres increases by 15% when the fibres are soaked in 5% aqueous solution of NaOH at 28±1° C for 72 to 76 h after which it shows a gradual decrease. This decrease is much more pronounced when the alkali is replenished after every 24 h. SEM observations showed the removal of cuticle and tyloses from the surface of coir as a result of alkali treatment, resulting in a rough fibre surface with regularly spaced pits. The debonding stress of alkali-treated fibres from polyester matrix was 90% higher than that of untreated fibres from the same matrix. Untreated fibres tended to float in the polyester whereas alkali-treated fibres were uniformly dispersed in polyester. Incorporation of 0.30 volume fraction of untreated and treated fibres in polyester resulted in composites having 11% and less 5% porosity, respectively. Flexural strength, modulus and impact strength of composites containing alkali-treated fibres were 40% higher than those containing the same volume fractions of untreated fibres. Longitudinal ultrasonic velocity and sound attenuation measurements indicated less fibre segregation and better fibre-matrix bonding in composites containing alkali-treated fibres.