A review on development of natural fiber reinforced polymer composites and properties of thermosetting materials
1A.Ramesh, 2N.V. Srinivasulu, 3P.Sunil Kumar
1,3Mechanical Engineering Department, Malla Reddy Engineering College, Dhullapally, Hyderabad, Telangana, India,
2Mechanical Engineering Dept., Chaitanya Bharati Institute of Technology, Gandipet, Hyderabad, Telangana, India.
Abstract—The abundant availability and accessibility of natural fibers are the major reasons for an emerging new interest in sustainable technology. Natural fibers, as reinforcement, have recently attracted the attention of researchers because of their advantages over other established materials. They are environmentally-friendly, fully biodegradable, abundantly available, non-toxic, non- abrasive, renewable, and cheap, and have low density), Modern composite materials constitute a significant proportion of the engineered materials market ranging from everyday products to sophisticated niche applications.
While composites have already proven their worth as weight-saving materials, the current challenge is to make them cost effective. This review paper discuss about worldwide review report on natural fibers and its applications. Also, this paper concentrates on biomaterials progress in the field of orthopedics. An effort to utilize the advantages offered by renewable resources for the development of biocomposite materials based on bio epoxy resin and natural fibers such as Agave sisalana, Musa sepientum; Hibiscus sabdariffa and its application in bone grafting substitutes.
Keywords—Fiber Reinforced Polymer, biodegradable, Thermosets, Thermoplastics, Extraction of cellulose, Properties of Natural fibres.
I. INTRODUCTION
1.1. Definition of composite:
The most widely used meaning is the following one, which has been stated by Jartiz “Composites are multifunctional material systems that provide characteristics not obtainable from any discrete material.
They are cohesive structures made by physically combining two or more compatible materials, different in composition and characteristics and sometimes in form”. The weakness of this definition resided in the fact that it allows one to classify among the composites any mixture of materials without indicating either its specificity or the laws which should given it which distinguishes it from other very banal, meaningless mixtures.
1.2. Merits of Composites:
Advantages of composites over their conventional counterparts are the ability to meet diverse design requirements with significant weight savings as well as strength-to-weight ratio. Some advantages of composite materials over conventional ones are as follows:
Tensile strength of composites is four to six times greater than that of steel or aluminum (depending on the reinforcements).Improved torsional stiffness and impact properties. Higher fatigue endurance limit (up to 60% of ultimate tensile strength).30% - 40% lighter for example any particular aluminum structures designed to the same functional requirements. Composites enjoy reduced life cycle cost compared to metals. Composites exhibit excellent corrosion resistance and fire retardancy.Broadly; composite materials can be classified into three groups on the basis of matrix material. They are:
a) Metal Matrix Composites:
Metal Matrix Composites have many advantages over monolithic metals like higher specific modulus, higher specific strength, better properties at elevated temperatures, and lower coefficient of thermal expansion. Because of these attributes metal matrix composites are under consideration for wide range of applications viz. combustion chamber nozzle (in rocket, space shuttle), housings, tubing, cables, heat exchangers, structural members etc.
b) Ceramic matrix Composites:
One of the main objectives in producing ceramic matrix composites is to increase the toughness. Naturally it is hoped and indeed often found that there is a concomitant improvement in strength and stiffness of ceramic matrix composites.
c) Polymer Matrix Composites:
Most commonly used matrix materials are polymeric.
The reason for this is twofold. In general the mechanical properties of polymers are inadequate for many structural purposes. In particular their strength and stiffness are low compared to metals and ceramics.
These difficulties are overcome by reinforcing other materials with polymers. Secondly the processing of polymer matrix composites need not involve high pressure and doesn’t require high temperature. Also equipments required for manufacturing polymer matrix composites are simpler. For this reason polymer matrix composites developed rapidly and soon became popular for structural applications. Composites are used because overall properties of the composites are superior to those of the individual components for example polymer/ceramic.
II. GENERAL TYPES OF MATRIX MATERIALS
In general, following general following types of matrix materials are available:
• Thermosetting material, • Thermoplastic material
• Carbon, Metals, Ceramics & Glass Matrix. Composites have a greater modulus than the polymer component but aren’t as brittle as ceramics. Two types of polymer composites are
Table1
Thermosets Thermoplastics
Resin cost is low. Resin cost is slightly higher.
Thermoset exhibit moderate shrinkage.
Shrinkage of thermoplastics is low Interlaminar fracture
toughness is low.
Interlaminar fracture toughness is high.
Thermosets exhibit good resistance
Thermoplastics exhibit poor resistance Prepregability
characteristics are excellent
Prepregability
characteristics are poor.
Prepreg shelf life and out time are poor.
Prepreg shelf life and out time are excellent.
Different types of thermosets and thermoplastic resins commonly in use are as follows:
Table2
Thermosets Thermoplastics
Phenolics & Cyanate ester Polypropylene Polyesters & Vinyl esters Nylon (Polyamide)
Polyimides Poly-ether-imide (PEI)
Epoxies Poly-ether-sulphone
(PES)
Bismaleimide (BMI) Poly-ether-ether-ketone (PEEK)
3.1 Fiber Reinforced Polymer
Common fiber reinforced composites are composed of fibers and a matrix. Fibers are the reinforcement and the main source of strength while matrix glues all the fibers together in shape and transfers stresses between the reinforcing fibers. The fibers carry the loads along their longitudinal directions. Sometimes, filler might be added to smooth the manufacturing process, impact special properties to the composites, and / or reduce the product cost. Common fiber reinforcing agents include asbestos, carbon / graphite fibers, beryllium, beryllium carbide, beryllium oxide, molybdenum, aluminium oxide, glass fibers, polyamide, natural fibers etc.Similarly common matrix materials include epoxy, phenolic,polyester, polyurethane, polyetherethrketone (PEEK), vinyl ester etc. Among these resin materials, PEEK is most widely used. Epoxy, which has higher adhesion and less shrinkage than PEEK, comes in second for its high cost.
3.2 Particle Reinforced Polymer
Particles used for reinforcing include ceramics and glasses such as small mineral particles, metal particles such as Aluminium and amorphous materials, including polymers and carbon black. Particles are used to increase the modules of the matrix and to decrease the ductility of the matrix. Particles are also used to reduce the cost of the composites. Reinforcements and matrices can be common, inexpensive materials and are easily processed. Some of the useful properties of ceramics and glasses include high melting temp., low density, high strength, stiffness; wear resistance, and corrosion resistance. Many ceramics are good electrical and thermal insulators. Some ceramics have special properties; some ceramics are magnetic materials; some are piezoelectric materials; and a few special ceramics are even superconductors at very low temperatures.
Against this backdrop, the present work has been taken up to develop a series of PEEK based composites with glass fiber reinforcement and with ceramic fillers and to study their response to solid particle erosion.
3.3 Characteristics of the Composites
A composite material consists of two phases. It consists of one or more discontinuous phases embedded in a continuous phase. The discontinuous phase is usually harder and stronger than the continuous phase and is called the reinforcement„ or „reinforcing material‟, whereas the continuous phase is termed as the matrix.
The matrix is usually more ductile and less hard. It holds the dispersed phase and shares a load with it. Matrix is composed of any of the three basic material type i.e.
polymers, metals or ceramics. The secondary phase embedded in the matrix is a discontinuous phase. It servers to strengthen the composites and improves the overall mechanical properties of the matrix. Properties of composites are strongly dependent on the properties
of their constituent materials, their distribution and the interaction among them. Apart from the nature of the constituent materials, the geometry of the reinforcement (shape, size and size distribution) influences the properties of the composite to a great extent.which plays an important role in determining the extent of the interaction between the reinforcement and the matrix.
Concentration, usually measured as volume or weight fraction, determines the contribution of a single constituent to the overall properties of the composites.
3.4 Natural Fiber Reinforced Composites
The interest in natural fiber-reinforced polymer composite materials is rapidly growing both in terms of their industrial applications and fundamental research.
They are renewable, cheap, completely or partially recyclable, and biodegradable. Plants, such as flax, cotton, hemp, jute, sisal, kenaf, pineapple, ramie, bamboo, banana, etc., as well as wood, used from time immemorial as a source of lignocellulosic fibers, are more and more often applied as the reinforcement of composites. The natural fiber-containing composites are more environmentally friendly, and are used in transportation (automobiles, railway coaches, aerospace), military applications, building and construction industries (ceiling paneling, partition boards), packaging, consumer products, etc.
III. CLASSIFICATION OF NATURAL FIBERS
They can also be matted into sheets to make products such as paper or felt. Fibers are of two types: natural fiber and manmade or synthetic fiber.
Figure 1
1) Animal Fibers: Animal Fibers contains wool, silk, avian fiber. It includes sheep’s wool, goat hair, horse hair, feathers and feathers fiber.
2) Mineral fiber: Mineral fibers are naturally occurring fiber or slightly modified fiber procured from minerals.
These can be further categorized as asbestos, Ceramic, Metal fiber.
3) Plant fiber: Plant fibers are generally comprised mainly of cellulose. This fiber can be further categorizes into following.
a) Seed fiber: Fibers collected from the seed and seed case e.g. cotton and kapok
b) Leaf fiber: Fibers collected from the leaves e.g. sisal and agave.
c) Skin fiber: Fibers are collected from the skin or bast surrounding the stem of their respective plant.
These fibers have higher tensile strength than other fibers. Therefore, these fibers are used for durable yarn, fabric, packaging, and paper. Some examples are flax, jute, banana, hemp, and soybean.
d) Fruit fiber: Fibers are collected from the fruit of the plant, e.g. coconut (coir) fiber.
e) Stalk fiber: Fibers are actually the stalks of the plants such as straws of wheat, rice, barley, and other
crops including bamboo and grass. Tree wood is also such a fiber.
Figure 2
IV. APPLICATIONS OF NATURAL FIBER COMPOSITES
The natural fiber composites can be very cost effective material for following applications:
Building and construction industry: panels for partition and false ceiling, partition boards, wall, floor, window and door frames, roof tiles, mobile Storage devices: post-boxes, bio-gas containers,
etc.
Furniture: chair, table, shower, bath units, etc.
Electric devices: electrical appliances, pipes, etc.
Everyday applications: lampshades, suitcases, helmets, etc.
Transportation: automobile and railway coach interior, boat, etc. The reasons for the application of natural fibers in the automotive industry include:
Low density: which may lead to a weight reduction of 10 to 30% Acceptable mechanical properties, good acoustic properties.
Price advantages both for the fibers and the applied technologies.
V. ADVANTAGES OF NATURAL FIBER COMPOSITES
The main advantages of natural fiber composite are:
Low specific weight, resulting in a higher specific strength and stiffness than glass fiber.
Producible with low investment at low cost, which makes the material an interesting product for low wage countries.
Reduced wear of tooling, healthier working condition, and no skin irritation.
Thermal recycling is possible while glass causes problem in combustion furnaces.
Good thermal and acoustic insulating properties.
VI. TYPICAL PROPERTIES OF THERMOSETTING MATERIALS
Salient properties of some of the above-referred thermosetting materials are given in the following paras.
7.1 Phenolics:
• Low cost, Capability to be B-Staged,
• Excellent high temperature resistance up to 205- 260°C (400-500°F), Good mechanical strength,
• Dimensional and thermal stability, Good laminate properties,
• Hot molding (cold molding),Curing temperature is 175°C
• High chemical resistance and good dielectric
properties.
Some of the disadvantages are: by-products are produced during curing, there is high shrinkage on cure, and phenolic laminates are porous.
7.2 Polyesters:
• Low cost, good handling characteristics,
• Low viscosity and versatility, Curing temperature is 120°C
• Good mechanical strength, Good electrical properties,
• Good heat résistance, cold and hot molding, Some of the disadvantages are: interlaminar shear is less than that of epoxies, lower strength than that of epoxies, fair weatherability, high curing shrinkage, and poor chemical resistance.
7.3 Vinyl Ester:
• Vinyl ester combines inherent toughness with outstanding heat and chemical resistance,
• Corrosion-resistance, and Possesses low ester content and low
• Unsaturation resulting in greater resistance to hydrolysis and less shrinkage during cure.
Some of the disadvantages are: vinyl esters are not as good as epoxy resins with regard to bond ability and high cost.
7.4 Polyimides:
• Excellent strength retention for long term in 260- 315°C range and short term in 370°C range,
• Excellent electrical properties, mechanical strength,
• Good fire resistance and low smoke emission,
• Hot molding & Curing temperature is 175°C and 315°C
7.5 Epoxies:
• Make an excellent matrix material because of their versatility,
• Good handling characteristics, Low shrinkage,
• Good chemical résistance, mechanical properties,
• Offer considerable variety for formulating Prepreg resins,
• Hot molding (cold molding rarely), High smoke emission,
• Curing temperature is 120-175°C
Some of the disadvantages are: require 4.4°C storage and shipment, service temperature is only 93-1O7°C)and laminate displays light brittleness.
VII. LITERATURE SURVEY
Researchers have begun to focus attention on natural fiber composites (i.e., biocomposites), which are composed of natural or synthetic resins, reinforced with natural fibers. Natural .bers exhibit many advantageous properties, they
are a low-density material yielding relatively lightweight composites with high specific properties. These fibers also o.er signi.cant cost advantages and ease of processing along with being a highly renewable resource, in turn reducing the dependency on foreign and domestic petroleum oil. Recent advances in the use of natural fibers (e.g. cellulose, jute, hemp, straw, switch grass, kenaf, coir and bamboo) in composites have been reviewed by several authors [6–25]. Harish et al. [2]
developed coir composite and mechanical properties were evaluated. Scanning electron micrographs obtained from fracture surfaces were used for a qualitative evaluation of the interfacial properties of coir /epoxy and compared with glass fibers. Wang and Huang [1] had taken a coir fiber stack; characters of the fibers were analyzed. Length of the fibers was in the range between 8 and 337 mm. The fibers amount with the length range of 15~145 mm was 81.95% of all measured fibers. Weight of fibers with the length range of 35~225 mm accounted for 88.34% of all measurement. The average fineness of the coir fibers was 27.94 tex. Longer fibers usually had higher diameters. Composite boards were fabricated by using a heat press machine with the coir fiber as the reinforcement and the rubber as matrix. Tensile strength of the composites was investigated. Nilza et al.
[3] use three Jamaican natural cellulosic fibers for the design and manufacture of composite material. They took bagasse from sugar cane, banana trunk from banana plant and coconut coir from the coconut husk. Samples were subjected to standardized tests such as ash and carbon content, water absorption, moisture content, tensile strength, elemental analysis and chemical analysis. Bilba et al.The solid residues obtained were analyzed by classical elemental analysis, Fourier Transform Infra Red (FTIR) spectroscopy and were observed by Scanning Electron Microscopy (SEM.
VIII. EXTRACTION OF CELLULOSE
Extraction of cellulose is carried out by a chemical procedure called water pre hydrolysis Fibers were cut to an approximate length of 1 cm The fibers are which are 3-4long are cut into approximate length of 5mm-10mm with the help of scissor, Washed with distilled water and dried in oven at 80˚C for 24 hours. The chopped fibers are kept in beaker and washed with distilled water for 20min-30min and then these washed fibers are dried in an oven at a temperature of 80˚C for 24 hours Dew axing step-Boiling fibers in a mixture of toluene/ethanol (2:1 vol/vol) in a Soxhlet extractor for 6 hours. The washed fibers then proceeded with Dewaxing step.
Boiling of these fibers in soxhlet extractor is carried out at a temperature of 70˚C for 6 hours, washed with ethanol for 30 min and then made to dry . Pre-treated fiber is then mixed with 0.1M NaOH in 50% volume of ethanol at 45˚C for 3 hours under continuous stirring.
The pretreated fibers are mixed with the prepared solution in a beaker and the beaker is placed on magnetic stirrer then it should be heated at 45˚C(Degree centigrade) for 3hours under continuous agitation.
Then treatment with H2O2 at pH=10.5(buffer solution) and 45˚C.(a)0.5% H2O2 (b)1% H2O2 (c)2% H2O2 (d)3% H2O2 for 3 hours each under continuous agitation.
The fibers are now treated different concentrations which were prepared. Then each solution is poured in beaker Containing fibers and it is kept on a magnetic stirrer and heated at a temperature of 45˚C for 3hours under continuous agitation. A buffer solution of pH=10.5 is mixed every time with each prepared solution.
Then mixture is treated with 10% w/v NaOH + 1% w/v Na2B4O7.10H2O at 32˚C for 15 hours under continuous stirring. Now the fibers are again treated with the prepared mixture and it should be poured in beaker containing fibers and kept on magnetic stirrer and it should be heated at a temperature of 32˚C for 15 hours under continuous agitation Finally mixture is treated capable of maintaining uniform temperatures of The specimens are placed in ove at 50 ± 3oC for 24 hr to evaporate any water partices in specimen and weight (conditioned) of specimen is noted .The conditioned specimens shall be placed in a container of double distilled water maintained at a temperature of 23 ± 1°C and shell rest on edge and be entirely immersed. After 24 hours, the specimens shall be removed from water, all surface water wiped off with a dry cloth, and weighed immediately, and again the specimens are kept in oven for 24 hours for reconditioning, and weight (reconditioned) of specimen is noted.
IX. PROPERTIES OF NATURAL FIBERS
Table 3
Fibre Type Density Kg/m3
Modulus of Elasticity (GPa)
Tensile Strength (MPa)
Sisal 800-700 16 250-270
Roselle 800-750 17 17030
Banana 950-750 23 180-430
Date Palm 450-470 70 125-200
Coconut 145-380 19-26 120-200
Reed 490 37 70-140
Coir 1200 4-6 150-180
Bamboo 1400 30-40 500-740
Jute 1300 20-50 300-700
Hemp 1480 30-60 350-800
Flax 1450 50-70 500-900
10.1 Tensile Testing:
In a broad sense, tensile test is a measurement of the ability of a material to withstand forces that tend to pull it
apart and to what extent the material stretches before breaking. The stiffness of a material which represented by tensile modulus can be determined from stress-strain diagram. The specimens were positioned vertically in the grips of the testing machine. The grips were then tightened evenly and firmly to prevent any slippage with gauge length kept at 30mm. As the tensile test starts, the specimen elongates the resistance of the specimen increases and is detected by a load cell. This load value (F) is recorded until a rupture of the specimen occurred.
10.2 Flexural Testing:
Flexure testing is often done on relatively flexible materials such as polymers, wood and composites. 3- point flex in a 3-point test the area of uniform stress is quite small and concentrated under the center loading point. Specimens for flexural test are cut from laminates as per ASTM D792 standards. Flexural strength is the ability of the material to withstand bending forces applied perpendicular to its longitudinal axis. Sometime it is referred as cross breaking strength where maximum stress developed when a bar-shaped test piece, acting as a simple beam, is subjected to a bending force perpendicular to the bar. This stress decreased due to the flexural load is a combination of compressive and tensile stresses. There are two methods that cover the determination of flexural properties of material: three- point loading system and four point loading system. As described in ASTM D790, three-point loading system applied on a supported beam was utilized. Flexural test is important for designer as well as manufacturer in the form of a beam.
10.3 Water Absorption:
This test method covers the determination of the relative rate of absorption of water by plastics when immersed. This test method intended to apply to the testing of all types of plastics, including cast, hot molded and cold molded resinous products, and both homogenous and laminated plastics in rod and tube form and in sheets0.13mm(0.005inch) or greater in thickness. This test method covers the determination of the relative rate of absorption of water by fiber when immersed. and dimensions. Specimens for water absorption test are cut from laminates as per ASTM 570 standards.
X. CONCLUSION
A lot of research has been done on natural fiber reinforced polymer composites but research on such as Plants,Sisal (Agave sisalana), Banana (Musa sepientum),Roselle (Hibiscus sabdariffa) flax, cotton, hemp, jute, kenaf, pineapple, ramie, bamboo, banana, polymer composites is very rare. Against this background, the present research work has been undertaken, with an objective to explore the potential of the above said fiber polymer composites and to study the mechanical and material characterization of different composites. In future, the final composite material coated by calcium phosphate and hydroxyapatite (hybrid) composite can be used for both internal and external fixation on the human body for fractured bone.
Further improvements can be expected, so that it might become possible to substitute technical-fibers in composites quite generally. Natural fibers are low-cost, recyclable and
Eco-friendly materials. Eco-friendliness and bio- degradability of these natural fibers may replace the glass and carbon fibers.
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