Flexure Testing of Fibre-Reinforced Plastic Composites - Literature review Example

Flexure Testing of Fibre-Reinforced Plastic Composites Introduction A fibre-reinforced polymer is a fundamental composite material possessing a polymer matrix mainly embedded with high strength fibres. High strength fibres include glass, aramid, and carbon. The polymer is primarily categorized into thermoplastics and thermosetting. Thus, thermoplastic materials are rampant as matrices for the bio fibres. Moreover, thermoplastics are utilized as the matrix in polypropylene, polyethylene, and corresponding polyvinyl chloride. Conversely, epoxy and polyester resins are the conventional thermosetting matrices. Glass Fiber Reinforced Polymers is the fiber reinforced is developed from the plastic matrix reinforced by the fine fibers of glass. The fiberglass is typically frivolous, durable and robust material utilized in diverse industries because of their excellent properties. The composites materials are applicable for the aerospace, construction, packaging and automotive industries. Nevertheless, there is the drawback of the polymers composites due to the unsuitability amidst the hydrophilic natural fibres and corresponding hydrophobic thermoplastic matrices, which results in undesirable properties of the underlying composites. Thus, it is fundamental to adjust the grain surface by using chemical adjustments in the bid to advance the bond amidst fibre and matrix. Different standards of ASTM apply to a wide range of fiber-reinforced polymer matrix composite materials. ASTM standard testing (or test) methods, as well as several other supporting standards, apply to fiber-reinforced polymer matrix materials. Flexural testing provides a detailed procedures and analysis of various composite testing standards, including the non-ASTM test methods. The user of any given standard has a responsibility to establish the most appropriate health and safety practices, as well as to determine the regulatory limitations of particular standards Factors influencing the underlying performance of natural fiber reinforced composites besides the hydrophilic nature of the fibre. The other properties of the natural fibre reinforced composites are fibre content. The high quantity of fibre is essential for accomplishing the high performance of the composites. Thus, the impact of fibre content regarding the properties of natural fibre reinforced composites is crucial (Vinícius et al., 2008, pp. 124-178). Moreover, increase in the fibre loading results to an escalation within the tensile properties. The parameter also employed significantly influence the properties and corresponding interfacial features of the composites products. Appropriate processing methods and underlying parameters ought to be carefully chosen to yield the prevailing optimum composite products. The paper aims at reviewing the Flexure testing of fibre-reinforced plastic matrix composites regarding the fiber loading, production methods, chemical treatments and corresponding procedure parameters on the tensile properties of the natural fiber reinforced composites. A reinforced concrete column is defined as plastic hinge regions during a strong earthquake (Mortezaei & Ronagh, 2012, p. 1365)). The column details and the characteristics of the earthquakes are the primary determinants of the formation or creation of a plastic hinge in the RC column. Fiber-Reinforced Plastics helps strengthen recently designed and constructed buildings and prevent near-fault earthquakes. A frame consisting of flexural members, connections and columns is designed and detailed so that it accommodates reversible lateral displacements once the plastic hinges have been formed (Mortezaei & Ronagh, 2012, p. 1366). RC frames often dissipate energy through flexural yielding at the plastic hinges. In particular, FRP is an efficient and viable method for strengthening the structure owing to its comparatively easy and quick installation. The material, ductility, damping, and type of structures are fundamental reasons for such massive losses considering the immense magnitude of forces induced by the earthquakes. Apparently, the invention entails various steps, such as disposing of FRP raw material inside a molding space. The molding space is created between the covering material and the mold. With the pressure, the plate is composed of spring steel in the molding method of the current invention the pressure plate is formed into a flat shape. Moreover, it can often elastically deform the shape of the fiber-reinforced plastic raw material. A molding load is being applied to the interior of the molding space, as well as the return to its original shape when the molding load is eventually released. Oats were covering material removed after curing the resin composition. The suppliers of Plastic additives’ effort to widen their product lines as well as offer services in areas, such as safety, testing, training, patent support, and numerous other internal capabilities (Blanco, 2002, p. 79). Moreover, the new growth areas for the plastic additive industry coupled with long fiber-reinforced thermoplastics, nanocomposites, wood composites, and conductive compounds. Environmentally friendly products such as non-halogenated flame retardants and organic heat stabilizers also constitute new growth areas for the additive industry (Blanco, 2002, 80). Another critical approach towards attaining the profit-enhancement strategy is to target the niche markets for resins. All plastic parts of a gadget or equipment have an ISO code for plastic identification (Thomas, 2012, p. 38). The ISO code is usually molded into the back, apparently highlighting the specific plastic type. For instance, the technician often uses an adhesion promoter before refinishing when the parts are made from olefin polymers (Thomas, 2012, p. 39). The adhesion promoter will ensure that the finish do not delaminate later. Meanwhile, refinishing the repaired plastic parts as well as completing the undamaged parts always requires varied preparation precautions ad steps. Comparisons the flexural strength of different veneering ceramics for zirconia mainly entails three-point flexural strength test. Moreover, this is done using ten different veneering ceramics for zirconia and three veneering ceramics for metal-ceramic technique (Fischer et al., 2008, p. 316). The ten veneering ceramics for zirconia is the test group while the three different veneering ceramics for metal-ceramic technique is the control group. The trio recognizes three fundamental methods (or techniques) for measuring the flexural strength namely the three-point flexure test, the four-point flexure strength, and the biaxial flexure strength test (Fischer et al., 2008, p. 318). The tests mentioned above often involve the application of static load to veneering ceramics for zirconia until failure. Carbon fiber-reinforced plastic (also referred to as carbon fiber-reinforced polymer) is a light and strong fiber-reinforced polymer consisting of carbon fibers. Although carbon fiber-reinforced polymers can be costly to produce, they are widely applied in cases where rigidity and high strength-to-weight ratio are a requisite. For instance, CFRPs have gained vast application in civil and automotive engineering, as well as aerospace, sports, and copious other technical and consumer applications (Vinícius et al., 2008, pp. 124-178). CFRP has also found extensive application in numerous high-end products, such as laptop cases, audio components, musical instruments, kite systems, firearms, and tripod legs. Even though several other thermoplastic polymers or thermosets such as vinyl ester, nylon, and polyester have been broadly used, the crucial polymer remains thermoset resin. A typical example of thermoset resin is epoxy. The type (or types) of additives introduced into resin (the binding matrix) can significantly affect the properties of the outcome (CFRP product). Silica is the most common additive used in the production of CFRPs. Other additives may include carbon nanotubes and rubber. Flexural Tests Four Point Flexural Test The Four Point Flexural Test (also known as the four-point bending test) provides values for flexural stress σf, modulus of elasticity in bending Ef, and flexural strain ϵf. It also provides values for the flexural stress-strain response of the material. The primary difference between the three-point flexural test and the four-point flexural test is that the latter contains an additional 4th bearing, which brings a larger portion of the beam to maximum stress (Baby et al., 2012, p. 545). The testing method often involves a particular test mixture placed on the universal testing machine. According to a study dubbed “Proposed Flexural Test Methods and Associated Inverse Analysis for Ultra-High-Performance Fiber-Reinforced Concrete” by Baby et al (2012), the four-point flexural test is highly useful to derive the tensile stress-strain response of composites (Baby et al., 2012, p. 545). Apparently, the details of test preparation, conduct, and conditioning usually affect the test results. The sample is a set distance apart placed on two supporting pins. Two loading pins is placed at equal distance from the center then lowered at the constant rate until sample failure. The principal advantages of four-point bending test include the simple test fixture, possibility to use fabricated materials, more uncomplicated sample geometries, and the fact that it requires the least sample machining (Vinícius et al., 2008, pp. 124-178). However, the main limitation of the four-point bending test is that it involves more complex, multifaceted distribution through the sample. Calculation of flexural stress (for a rectangular cross section) is given by the formula: σf = 3FL / 4bd2 Where, σf - is the flexural stress at midpoint of outer fibers F - Represents load at a particular point on the curve (load deflection curve, N) L – Represents support span, mm b – Represents the test beam width, mm d – Represents depth of beam tested, mm Meanwhile, the four-point flexural test ASTM D 7264 is a flexural testing standard published in 2006. ASTM D 7264 focuses mainly on the composite materials and often presents reasonably concise test conditions and guidelines (Baby et al., 2012, pp. 545-555). This testing standard specifies the specimen length as well as a quarter-point load location. The sample length dictates the thickness of the specimen for any given ℓ/t ratio. ASTM D7264 outlines the testing of fundamental flexural properties of the polymer matrix composites. To attain this, ASTM D7264 uses a bar of rectangular cross section reinforced/supported on a beam and often deflected at arguably constant rate. ASTM D7264 helps to determine the flexural properties of a polymer matrix composite, such as the stiffness, strength, and deflection/load behavior. The test method differs from other flexure techniques primarily because it was developed for use specifically with continuous FRP matrix composites (Vinícius et al., 2008, pp. 124-178). Apparently, the four-point flexural test method summarizes two vital procedures. The first procedure (Procedure A) outlines the three-point loading system essentially for center loading. The second procedure (Procedure B) describes the four-point loading system primarily for two (equal) loading joints (Goldsztein, 2012, p. 713). The test method is usually designed for matrix composites and employs 32:1 span-to-thickness standard ratio compared to other methods such as ASTM D790 or even ASTM D6272. Whereas ASTM D790 is a three-point flexure for plastics that uses 16:1 span-to-thickness ratio, ASTM D6272 is a four-point flexure. On the other hand, ISO 14125 is not only relatively new but also the most relevant non-ASTM standard. Other ASTM standards include D790, D2344, D3878, D5229, D5687, D6272, D6856, E177, E456, E1309, and E1434. Fiber length Fibre length distribution of any tow injection molded plates is measured utilizing a combination of an automatic and manual method. The position of the measurements is chosen to correspond mainly to the centre of the prevailing gauge length for the subsequent tensile measurements. Every sample is placed into the crucible and subsequently into the furnace set at 450 degrees for approximately 6 hours to burn the PP fraction (Baby et al., 2012, pp. 545-555). In order to avoid bias, the complete fibre assembly are typically scattered across the A4 transparent sheet and imaged utilizing a flatbed scanner. The image is then analysed two forms method using the ImageJ image processing software. For instance, automatic fibre recognition and the computation of the length of every image employed in the embedded code within the ImageJ based on original algorithms. The measured fibre length distributions at the four different positions chosen across the medium plate were found to be identical depicting no significant spatial variation within the average fibre length over the underlying region where the tensile were undertaken. Nevertheless, there was a measured difference between the fibre length distributions of the prevailing two plates made utilizing the two diverse processing situations. Comparison of the frequency distribution for the three plates Fibre orientation Fibre orientation is measured at diverse positions across the moulded sections utilizing the Leeds in-house built image analyzer. FOD was examined along the underlying centre line of the medium plate from the corresponding injection position to the bottom of the sample along the X-axis. The analysis of the orientation at each centre location of the medium plate is located at the X value (Baby et al., 2012, pp. 545-555). Fibre orientation is undertaken with respect to the second-order orientation averages, and the summation of the three averages equate to 1. Thus, the inspection of the averages stipulates distinctly preferred direction of the orientation and through the thickness of the structures. In case fibers are used, the length reduction within the injection-molding machine is massively reduced compared to the circumstances of the long fibers. Consequently, in the case of the underlying short fiber, a relatively narrow fiber length distribution will be seen. The mean fiber length thus characterizes short fibers with the real accuracy. FLD plays a less significant role as compared to the corresponding Fiber Orientation Distribution and the expression of fiber length with an experimentally attained average value is adequate. Rule of mixtures A composite is normally a combination of two or more materials. The formula for the Rule of Mixtures is utilized in the computation and prediction Young’s Modulus, density, Poisson’s ratio and corresponding ultimate tensile strength (Mortezaei & Ronagh, 2012, pp1365-89). UTS offer extremely optimistic prediction and measuring 50% of the test. Rule of the mixtures for the Young’s Modulus assumes that there are unidirectional fibers since the prediction of the Young’s Modulus within the fiber is in one direction (Baby et al., 2012, pp. 545-555). The Efficiency Factor or corresponding Krenchel factor is employed in the prediction of the effect of the fibre orientation on stiffness. It is utilized to factor the Rule of Mixtures formula according to the underlying fibre angle. Flexural strength (commonly referred to as bend strength) is the ability of a particular material to resist bend or deformation under load. It is usually a mechanical parameter especially for brittle materials. Flexural strength mostly involves use of the bending test where a typical specimen, which has rectangular or circular cross-section, is bent on yielding or fracture using the three-point bending test (Goldsztein, 2012, p. 715). Ordinarily, the flexural strength denotes the material’s highest stress at the point of rupture, usually measured in the form of stress (σ). In the event that the material employed is homogenous, the flexural strength will be same as tensile strength. However, homogenous materials with defects on their surfaces because of scratches often have higher tensile strength compared to the flexural strength. FRP is widely applicable in building and construction. Its low weight and low maintenance make it ideal for many construction and infrastructure projects. A mixture UP resins, fillers and glass fiber is applicable in casting of solid surfaces and synthetic marble for bathrooms, kitchen, and roof tiles. FRP is also a perfect alternative to the conventional materials for construction of wind generators and bridges mainly due to its low maintenance, durability, and low weight. The little weight property of FRP composites has primarily made the installation process easier. Moreover, the advent of FRP has completely transformed the marine industry. It has successfully replaced steel building methods and traditional wood, especially in the making of leisure boats. FRP is applied to construct boats of all sizes and shapes, such as sailing yachts and competition kayaks. In addition, the material is used for building naval vessels, including high-speed patrol boats, submarines, and mine hunters. FRP is also an ideal material for most automotive car bodies owing to its mouldability, high-quality surface finishes, and low weight. In particular, FRP is used in the making offenders, complete truck cabs, roofs, and tailgates. Properties such as heat resistance and high dimensional tolerance make FRP material high suitable for under-bonnet and structural parts, including valve covers, front assemblies, and engine sumps. Incidentally, a single multi-functional part (FRP part) can replace separate metal components. FRP enhances molding of complex and attractive shapes. Meanwhile, particular grades of UP resins offer high levels of fire redundancy as well as the low smoke emission. Such properties are essential requirements or provisions for public transport, particularly in trains and in-tunnel applications such as seating and cladding. Apart from transportation, FRP is also applicable in constructing pipes and chemical plant. The chemical industry widely uses FRP for the construction of chemical storage vessels, pipe work, and fume scrubbers due to its outstanding resistance to chemical attack and corrosion. For instance, epoxy vinyl ester and vinyl ester resins give unmatched levels of chemical resistance (Mortezaei & Ronagh, 2012, pp1365-89). The fibers commonly used to make FRP composite material include carbon, basalt, glass, or ceramics. Asbestos, wood, or papers are used to reinforce the polymer matrix. Glass reinforced polymers were the strongest and most resistive particularly to various deforming forces when fibers of the polymer matrix are parallel to the force put forth or being exerted. Additionally, FRP may be used to strengthen the columns, slabs, and beams of bridges and buildings. For instance, structural engineers can use FRP to increase the strength of the beams and slabs of buildings even after loading conditions have severely damaged those structures. Flexural strengthening and shear strengthening are the two fundamental techniques typically adopted to strengthen beams (Mortezaei & Ronagh, 2012, pp1365-89). Shear strengthening entails the use of FRP on the sides (web) of the member with the fibers oriented traverse to the longitudinal axis of the beam. Unlike shear strengthening, flexural reinforcement involves the application of FRP plates or sheets to the supported member’s tension face. Despite the significant benefits associated with FRP application to industry, the material also has several disadvantages. The significant limitations of FRP mainly pertain to cost, tensile strength, toxic components, heat deflection, flexural strength, and degradation. Steel is cheaper compared to FRP, even though; the latter is advanced and stronger. Also, the ability of the polymer to achieve similar tensile and flexural quality as steel remains a concern. As a result, steel could still be ideal for building as well as the construction of many building and bridges. Moreover, FRP, unlike steel, lose its strength over time particularly due to aging. FRP continues to find new applications in construction and modern industries. Innovations and development concerning the use of resin technology will ensure dynamic future for many FRP composite materials as highly cost-effective and versatile alternative to conventional materials such as concrete, wood, and metals (Mortezaei & Ronagh, 2012, pp1365-89). FRP is widely applicable to designs that entail or require a precise measure of modulus or strength of elasticity. Ordinarily, the non-reinforced plastics are economically or mechanically ill-suited to measure strength/modulus of elasticity. There exist a glass fibre reinforce PPS composite possessing thermal properties close to the corresponding constituent materials selected in the study. The thermal conductivity values for the underlying PPS matrix and corresponding glass fiber were 0.2W/m K and 1.04 W/m K respectively. The fiber content volume fraction was equivalent to the underlying value in the study. Experimentally measured fiber orientation is attained through assessment of the enlarged microscope images. .Conclusion In summation, the ever-growing demand for efficient, high quality and reliable materials or components has necessitated the need to conduct flexural tests in manufacturing, building and construction sectors. Different flexural test methods help to ascertain the ability of a material to resist bending or deformation under load. Flexural tests often stimulate the stresses of compression and tensile on a specimen. The most conventional flexural testing techniques are three-point and four-point flexural tests. The flexural test methods (or transverse beam tests) measure the behavior of materials that have been subjected to simple beam loading. The flexural strength, an essential aspect of flexural testing, denotes material’s highest stress at the point of rupture. The four-point flexural test provides values for the flexural stress-strain response of the material. It also contains an additional fourth bearing, which brings a larger portion of the beam to maximum stress. The two fundamental methods for testing the flexural strength entail both destructive, as well as non-destructive testing. Meanwhile, ASTM D7264 outlines the testing of the essential flexural properties of the polymer matrix composites. Fiber-Reinforced Plastic structures consist of mainly unsaturated polyester (UP) resin mostly applied to a mould along with reinforcement. Carbon fiber-reinforced polymers are widely used in cases where rigidity and high strength-to-weight ratio are vital. They have gained immense applications or usage in civil and automotive engineering, aerospace, sports, and many other technical and consumer applications. References Alaneme, K.K., Oke, S.R. & Omotoyinbo, J.A. 2014, "Mechanical Behaviour Of Oil Palm Ash- Oil Palm Fibre Hybrid Reinforced Polyester Matrix Composites", Annals of the Faculty of Engineering Hunedoara, vol. 12, no. 1, pp. 193-200. 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