Journal of Composites The latest articles from Hindawi Publishing Corporation © 2014 , Hindawi Publishing Corporation . All rights reserved. Effect of Fiber Geometry and Representative Volume Element on Elastic and Thermal Properties of Unidirectional Fiber-Reinforced Composites Tue, 18 Nov 2014 10:20:07 +0000 The aim of present work is focused on the evaluation of elastic and thermal properties of unidirectional fiber-reinforced polymer composites with different volume fractions of fiber up to 0.7 using micromechanical approach. Two ways for calculating the material properties, that is, analytical and numerical approaches, were presented. In numerical approach, finite element analysis was used to evaluate the elastic modulus and thermal conductivity of composite from the constituent material properties. The finite element model based on three-dimensional micromechanical representative volume element (RVE) with a square and hexagonal packing geometry was implemented by using finite element code ANSYS. Circular cross section of fiber and square cross section of fiber were considered to develop RVE. The periodic boundary conditions are applied to the RVE to calculate elastic modulus of composite. The steady state heat transfer simulations were performed in thermal analysis to calculate thermal conductivity of composite. In analytical approach, the elastic modulus is calculated by rule of mixture, Halpin-Tsai model, and periodic microstructure. Thermal conductivity is calculated analytically by using rule of mixture, the Chawla model, and the Hashin model. The material properties obtained using finite element techniques were compared with different analytical methods and good agreement was achieved. The results are affected by a number of parameters such as volume fraction of the fibers, geometry of fiber, and RVE. Siva Bhaskara Rao Devireddy and Sandhyarani Biswas Copyright © 2014 Siva Bhaskara Rao Devireddy and Sandhyarani Biswas. All rights reserved. Generation of R-Curve from 4ENF Specimens: An Experimental Study Wed, 12 Nov 2014 12:06:00 +0000 The experimental determination of the resistance to delamination is very important in aerospace applications as composite materials have superior properties only in the fiber direction. To measure the interlaminar fracture toughness of composite materials, different kinds of specimens and experimental methods are available. This article examines the fracture energy of four-point end-notched flexure (4ENF) composite specimens made of carbon/epoxy and glass/epoxy. Experiments were conducted on these laminates and the mode II fracture energy, , was evaluated using compliance method and was compared with beam theory solution. The crack growth resistance curve (R-curve) for these specimens was generated and the found glass/epoxy shows higher toughness values than carbon/epoxy composite. From this study, it was observed that R-curve effect in 4ENF specimens is quite mild, which means that the measured delamination toughness, , is more accurate. V. Alfred Franklin and T. Christopher Copyright © 2014 V. Alfred Franklin and T. Christopher. All rights reserved. Interfacial Adhesion Characteristics of Kenaf Fibres Subjected to Different Polymer Matrices and Fibre Treatments Thu, 06 Nov 2014 07:50:00 +0000 This study is aimed at determining the interfacial adhesion strength (IAS) of kenaf fibres using different chemical treatments in hydrochloric (HCl) and sodium hydroxide (NaOH) with different concentrations. Single fibre pullout tests (SFPT) were carried out for both untreated and treated fibres partially embedded into three different polymer matrices; polyester, epoxy, and polyurethane (PU) as reinforcement blocks and tested under dry loading conditions. The study revealed that kenaf fibres treated with 6% NaOH subjected to polyester, epoxy, and PU matrices exhibits excellent IAS while poor in acidic treatment. The effect of SFPT results was mainly attributed to chemical composition of the fibres, types of fibre treatments, and variation in resin viscosities. By scanning electron microscopy examination of the material failure morphology, the fibres experienced brittle and ductile fibre breakage mechanisms after treatment with acidic and alkaline solutions. Umar Nirmal, Saijod T. W. Lau, and Jamil Hashim Copyright © 2014 Umar Nirmal et al. All rights reserved. Multiscale Modeling of Elastic Properties of Sustainable Concretes by Microstructural-Based Micromechanics Sun, 02 Nov 2014 12:49:41 +0000 This paper addresses multiscale stiffness homogenization methodology to extract macroscale elastic mechanical properties of four types of sustainable concretes from their nanoscale mechanical properties. Nine different sustainable concrete mixtures were studied. A model based on micromechanics was used to homogenize the elastic properties. The hardened cement pastes were homogenized by three analytical methods based on Self-Consistent and Mori-Tanaka schemes. The proposed multiscale method combines advanced experimental and analytical methods in a systematic way so that the inputs are nanoscale phases properties extracted from statistical nanoindentation technique and mechanical properties of mixture ingredient. Predicted elastic properties were consistent with traditional experimental results. Linking homogenized mechanical properties of sustainable concrete to volume proportions through an analytical approach provides a critical first step towards rational optimization of these materials. V. Zanjani Zadeh and C. P. Bobko Copyright © 2014 V. Zanjani Zadeh and C. P. Bobko. All rights reserved. Effect of Chitosan Loading on the Morphological, Thermal, and Mechanical Properties of Diglycidyl Ether of Bisphenol A/Hexamethylenediamine Epoxy System Thu, 30 Oct 2014 07:43:01 +0000 The effect of chitosan filled diglycidyl ether of bisphenol A (DGEBA) epoxy system were investigated using the thermal, mechanical, and morphological properties. The mixing ratio of resin/hardener was kept constant while the chitosan of 1.0, 2.5, 5.0, 7.5, and 10 weight percentage (wt%) was incorporated into the system. The thermal stability and the transition behaviour of the chitosan filled epoxy system were analysed through a differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and Fourier transform infrared spectroscopy (FTIR) while atomic force microscope (AFM) and scanning electron microscopy (SEM) were used to investigate the morphology. It was observed that the additive tends to agglomerate, with the formation of clear phase separation, when the chitosan content increases above 5 wt%. At lower chitosan loading (2.5 wt% and below), relatively uniform dispersion of the additive can be achieved. The thermal stability of the system increases with chitosan loading while the mechanical tensile strength is compromised. B. Satheesh, K. Y. Tshai, and N. A. Warrior Copyright © 2014 B. Satheesh et al. All rights reserved. High Strain Rate Compressive Behavior of Polyurethane Resin and Polyurethane/Al2O3 Hollow Sphere Syntactic Foams Wed, 29 Oct 2014 00:00:00 +0000 Polyurethane resins and foams are finding extensive applications. Seat cushions and covers in automobiles are examples of these materials. In the present work, hollow alumina particles are used as fillers in polyurethane resin to develop closed-cell syntactic foams. The fabricated syntactic foams are tested for compressive properties at quasistatic and high strain rates. Strain rate sensitivity is an important concern for automotive applications due to the possibility of crash at high speeds. Both the polyurethane resin and the syntactic foam show strain rate sensitivity in compressive strength. It is observed that the compressive strength increases with strain rate. The energy absorbed up to 10% strain in the quasistatic regime is 400% higher for the syntactic foam in comparison to that of neat resin at the same strain rate. Dung D. Luong, Vasanth Chakravarthy Shunmugasamy, Oliver M. Strbik III, and Nikhil Gupta Copyright © 2014 Dung D. Luong et al. All rights reserved. Synthesis, Characterization, and Photoconductivity Studies on Poly(2-chloroaniline) and Poly(2-chloroaniline)/CuO Nanocomposites Tue, 14 Oct 2014 10:57:46 +0000 The poly(2-chloroaniline) and poly(2-chloroaniline)/CuO nanocomposites with various weight percentages (5%, 10%, 15%, 20%, and 25%) were synthesized by in situ chemical oxidative polymerization method using ammonium per sulphate (oxidant), HCl (dopant), and dodecyl benzene sulphonic acid as a surfactant at 0°C. The formation of polymer and its composites was confirmed by FTIR and UV-Visible spectroscopy. The SEM and X-ray diffraction studies clearly indicate the uniform dispersion of CuO nanoparticles into the polymer matrix. The thermal stability of the polymer and its composites increased with increase in the percentage of CuO nanoparticles. The polymer and composites exhibit fluorescence property and hence can be used in the light emitting diodes. The current voltage (I-V) curves clearly illustrate the enhanced conductivity on light exposure compared to the dark current. The conductivity of the polymer increased with increase in the percentage of CuO nanoparticles. Poly(2-chloroaniline)/CuO nanocomposites with 25% of CuO show a maximum conductivity of  S cm−1. The composites synthesized behave as organic metals due to their semiconducting nature. Porselvi Linganathan, Jency Sundararajan, and Jhancy Mary Samuel Copyright © 2014 Porselvi Linganathan et al. All rights reserved. Hybrid Fibre Polylactide Acid Composite with Empty Fruit Bunch: Chopped Glass Strands Tue, 14 Oct 2014 09:38:39 +0000 Hybrid polylactide acid (PLA) composites reinforced with palm empty fruit bunch (EFB) and chopped strand E-glass (GLS) fibres were investigated. The hybrid fibres PLA composite was prepared through solution casting followed by pelletisation and subsequent hot compression press into 1 mm thick specimen. Chloroform and dichloromethane were used as solvent and their effectiveness in dissolving PLA was reported. The overall fibre loading was kept constant at volume fraction, , of 20% while the ratio of EFB to GLS fibre was varied between of 0 : 20 to 20 : 0. The inclusion of GLS fibres improved the tensile and flexural performance of the hybrid composites, but increasing the glass fibre length from 3 to 6 mm has a negative effect on the mechanical properties of the hybrid composites. Moreover, the composites that were prepared using chloroform showed superior tensile and flexural properties compared to those prepared with dichloromethane. K. Y. Tshai, A. B. Chai, I. Kong, M. E. Hoque, and K. H. Tshai Copyright © 2014 K. Y. Tshai et al. All rights reserved. Sintering and Hardness Behavior of Fe-Al2O3 Metal Matrix Nanocomposites Prepared by Powder Metallurgy Wed, 10 Sep 2014 05:19:57 +0000 The present paper reports the investigations on sintering and hardness behavior of Fe-Al2O3 Metal Matrix Nanocomposites (MMNCs) prepared by Powder Metallurgy (P/M) route with varying concentration of Al2O3 (5–30 wt%). The MMNC specimens for the present investigations were synthesized by ball milling, followed by compaction and sintering in an inert atmosphere in the temperature range of 900–1100°C for 1–3 hours using Powder Metallurgy route. Phase and microstructures of the specimens were characterized by XRD and SEM. Reactive sintering takes place in these materials. During sintering nano iron aluminate (FeAl2O4) phase forms. Characterization was done by measuring density and hardness. Results have been discussed critically to illustrate the effect of various processing parameters on sintering and mechanical behavior. It is expected that the results of these investigations will be useful in developing Metal Matrix Nanocomposites (MMNCs) for typical industrial applications. Pallav Gupta, Devendra Kumar, Om Parkash, and A. K. Jha Copyright © 2014 Pallav Gupta et al. All rights reserved. Baseline Moisture Resistance of PWP Cement Composite Boards Reinforced with Internal Glass Fiber Reinforcement under Accelerated Wet-Dry Aging Tue, 05 Aug 2014 12:30:41 +0000 The purpose of this study was to improve the mechanical characteristics and moisture resistance of parawood particle (PWP) cement composite board developed by the authors. PWP cement composites were prepared with a mixture containing 15.0% parawood particles, 43.0% cement, 41.2% water, and 0.86% CaCl2 (by weight) and the PWP cement composite boards were internally reinforced with bidirectional glass fiber woven roving [0°/90°]. The board properties were evaluated under accelerated aging with wet-dry cycles to establish the durability and moisture resistance and the effect on flexural strength of the composite boards. The mechanical characteristics determined were the equivalent modulus of rupture (eMOR), the equivalent modulus of elasticity (eMOE), and the deformability factor (DF). The experimental results suggest that the strength and stiffness of the PWP composite boards with internal reinforcement are four times higher than those of the original PWP composite boards under accelerated aging based on 100 wet-dry cycles, implying better durability of the boards in outdoor use. The results provide a baseline to which improved formulations and reinforcements or designs can be compared using the same measurement methodology. Woraphot Prachasaree, Sitthichai Piriyakootorn, Suchart Limkatanyu, and Abideng Hawa Copyright © 2014 Woraphot Prachasaree et al. All rights reserved. The Shifts of Band Gap and Binding Energies of Titania/Hydroxyapatite Material Thu, 10 Jul 2014 08:40:31 +0000 The titania/hydroxyapatite (TiO2/HAp) product was prepared by precipitating hydroxyapatite in the presence of TiO(OH)2 gel in the hydrothermal system. The characteristics of the material were determined by using the measurements such as X-ray photoemission spectroscopy (XPS), X-ray diffraction (XRD), diffuse reflectance spectra (DRS), transmission electron microscopy (TEM), scanning electron microscopy (SEM), and energy dispersive X-ray (EDX). The XPS analysis showed that the binding energy values of Ca (2p1/2, 2p3/2), P (2p1/2, 2p3/2), and O 1s levels related to hydroxyapatite phase whereas those of Ti (2p3/2, 2p1/2) levels corresponded with the characterization of titanium (IV) in TiO2. The XRD result revealed that TiO2/HAp sample had hydroxyapatite phase, but anatase or rutile phases were not found out. TEM image of TiO2/HAp product showed that the surface of the plate-shaped HAp particles had a lot of smaller particles which were considered as the compound of Ti. The experimental band gap of TiO2/HAp material calculated by the DRS measurement was 3.6 eV, while that of HAp pure was 5.3 eV and that of TiO2 pure was around 3.2 eV. The shift of the band gap energy of TiO2 in the range of 3.2–3.6 eV may be related to the shifts of Ti signals of XPS spectrum. Nguyen Thi Truc Linh, Phan Dinh Tuan, and Nguyen Van Dzung Copyright © 2014 Nguyen Thi Truc Linh et al. All rights reserved. Multifunctional Thermally Remendable Nanocomposites Mon, 07 Jul 2014 12:26:57 +0000 Challenges associated with damage tolerance in polymer matrix composites must be successfully addressed in order to ensure highly reliable structures with significant weight savings. Self-healing materials provide a viable means to surmount damage tolerance concerns, thereby allowing for the realization of the mass reduction such structures have promised but not yet achieved. Introduction of multifunctional properties into self-healing composites can further extend their usefulness. This study examines the incorporation of carbon nanotubes into a self-healing composite in order to achieve this. Composite panels were fabricated with carbon fibers, a bismaleimide tetrafuran (2MEP4F) polymer resin, and various carbon nanotube materials. The composites exhibit enhancement in electrical, mechanical, and thermal properties. The healing mechanism is a thermally activated reversible polymerization of the 2MEP4F resin. The proposed method of heating exploits the enhanced microwave absorption inherent to carbon nanotubes to provide the thermal energy required for the reversible polymerization. Microwave testing demonstrated that the heating efficiency is increased, allowing uniform heating to the required temperature for polymer healing. Impacted composites show localized heating at the damage site, which implies that microwave heating can also be used as a means for damage detection and potential structural health monitoring. Edward D. Sosa, Thomas K. Darlington, Brian A. Hanos, and Mary Jane E. O’Rourke Copyright © 2014 Edward D. Sosa et al. All rights reserved. Effect of Linear Chain Carboxylic Acid Anhydrides on Physical and Mechanical Properties of Rubber (Hevea brasiliensis), Acacia, (Acacia spp.), and Oil Palm (Tinnera spp.) Woods Thu, 22 May 2014 10:43:30 +0000 The physical and mechanical properties of Rubber wood, Acacia wood, and Oil palm wood that reacted with acetic, propionic, and butyric anhydrides using a microwave heating for 4 minutes were investigated. A sample dimension of 300 mm × 100 mm × 25 mm () was used for modification and they were cut into smaller specimens for different testing method. This study found that the density increment and void volume changes were not significantly different from anhydrides. The modification of wood with anhydrides was not significantly affected by the static bending properties, except for the Oil palm. The compression strength for any anhydrides shows an improvement for the Rubber wood and Acacia spp. but not Oil palm. The hardness was also not significantly different from anhydrides for all wood species. The impact strength of Rubber wood and Oil palm significantly increased compared to the untreated wood, but this was not the case for Acacia spp. Generally, the highest improvement in mechanical properties was obtained by modification of Rubber and Acacia woods with butyric anhydride. Mohd Afiq Mohtar, Norul Hisham Hamid, and Mohd Hamami Sahri Copyright © 2014 Mohd Afiq Mohtar et al. All rights reserved. Multiscale Modeling of Residual Stress Development in Continuous Fiber-Reinforced Unidirectional Thick Thermoset Composites Mon, 24 Mar 2014 09:27:58 +0000 The primary objective of this research is to develop a multiscale simulation framework to arrive at more realistic estimates of cure-induced residual stresses in the vicinity of the fiber-matrix interface in thick thermoset composites. The methodology involves simulations at the part level—employing homogenized rendering of the composite using micromechanics approach—within a finite element framework to obtain part-level temperature and degree-of-cure gradients and strains, and imposition of this information as boundary conditions at the mesoscale simulations, employing microstructural representative volume elements (RVE). A simple implementation of the multiscale framework, involving simulations at the part as well as the RVE levels, is demonstrated in the context of a thick, unidirectional continuous-glass-fiber-reinforced thermoset composite. The trends in the mesoscale residual stresses estimated by employing different RVE-level thermal and thermomechanical boundary conditions—displaying different degrees of coupling between the global and part-level simulations—are then examined. Significant differences are observed in the estimates of mesolevel cure-induced residual stress evolution obtained from simulations with a conventional symmetric RVE and those obtained by employing the multiscale approach involving detailed boundary conditions that realistically account for global thermal and mechanical strain histories. Bhaskar Patham and Xiaosong Huang Copyright © 2014 Bhaskar Patham and Xiaosong Huang. All rights reserved. Validating the Classical Failure Criteria for Applicability to the Notched Woven-Roving Composite Materials Mon, 24 Mar 2014 07:04:39 +0000 The classical failure criteria are phenomenological theories as they ignore the actual failure mechanism and do not concentrate on the microscopic events of failure. The main objective of the current investigation is to modify the classical failure theories to comprise the essential failure mechanism (interfacial shear failure) in the thin-layered woven-roving composite materials. An interfacial shear correction factor (MH6) is introduced into the nondimensional shear terms in the studied classical failure criteria. Thus the validity of applying these theories to the investigated material will be augmented. The experimental part of the current study is conducted on thin-layered circular specimens. The specimens are fabricated from two plies of fiber E-glass woven-roving fabric reinforced with polyester. The fabrics are laid to have [45°] or [0°, 90°] fiber orientation. The specimens used are plain, where no macroscopic sources of stress concentration exist or having circular notches of five, seven, or nine mm radii. The specimens are subjected to low cycle completely reversed fatigue bending loading where the S-N and the R.D.-N curves are plotted for each group of specimens. Mohamed Mostafa Yousef Bassyouny Elshabasy Copyright © 2014 Mohamed Mostafa Yousef Bassyouny Elshabasy. All rights reserved. Effect of Moisture Absorption Behavior on Mechanical Properties of Basalt Fibre Reinforced Polymer Matrix Composites Thu, 20 Mar 2014 06:35:51 +0000 The study of mechanical properties of fibre reinforced polymeric materials under different environmental conditions is much important. This is because materials with superior ageing resistance can be satisfactorily durable. Moisture effects in fibre reinforced plastic composites have been widely studied. Basalt fibre reinforced unsaturated polyester resin composites were subjected to water immersion tests using both sea and normal water in order to study the effects of water absorption behavior on mechanical properties. Composites specimens containing woven basalt, short basalt, and alkaline and acid treated basalt fibres were prepared. Water absorption tests were conducted by immersing specimens in water at room temperature for different time periods till they reached their saturation state. The tensile, flexural, and impact properties of water immersed specimens were conducted and compared with dry specimens as per the ASTM standard. It is concluded that the water uptake of basalt fibre is considerable loss in the mechanical properties of the composites. Amuthakkannan Pandian, Manikandan Vairavan, Winowlin Jappes Jebbas Thangaiah, and Marimuthu Uthayakumar Copyright © 2014 Amuthakkannan Pandian et al. All rights reserved. Hybrid Carbon-Carbon Ablative Composites for Thermal Protection in Aerospace Thu, 06 Mar 2014 07:17:43 +0000 Composite materials have been steadily substituting metals and alloys due to their better thermomechanical properties. The successful application of composite materials for high temperature zones in aerospace applications has resulted in extensive exploration of cost effective ablative materials. High temperature heat shielding to body, be it external or internal, has become essential in the space vehicles. The heat shielding primarily protects the substrate material from external kinetic heating and the internal insulation protects the subsystems and helps to keep coefficient of thermal expansion low. The external temperature due to kinetic heating may increase to about maximum of 500°C for hypersonic reentry space vehicles while the combustion chamber temperatures in case of rocket and missile engines range between 2000°C and 3000°C. Composite materials of which carbon-carbon composites or the carbon allotropes are the most preferred material for heat shielding applications due to their exceptional chemical and thermal resistance. P. Sanoj and Balasubramanian Kandasubramanian Copyright © 2014 P. Sanoj and Balasubramanian Kandasubramanian. All rights reserved. Effect of Melt Temperature and Hold Pressure on the Weld-Line Strength of an Injection Molded Talc-Filled Polypropylene Wed, 05 Mar 2014 15:47:33 +0000 Tensile stress-strain behavior coupled with fractography was used to investigate the weld-line strength of an injection molded 40 w% talc-filled polypropylene. The relationship between processing conditions, microstructure, and tensile strength was established. Fracture surface of the weld line exhibited skin-core morphology with different degrees of talc particle orientations in the core and in the skin. Experimental results also showed that the thickness of the core decreased and the thickness of the skins increased with increasing melt temperature and increasing hold pressure, which resulted in an increase of yield strength and yield strain with increasing melt temperature and increasing hold pressure. Finally, a three-parameter nonlinear constitutive model was developed to describe the strain softening behavior of the weld-line strength of talc-filled polypropylene. The parameters in this model are the modulus E, the strain exponent m, and the compliance factor β. The simulated stress-strain curves from the model are in good agreement with the test data, and both m and β are functions of skin-core thickness ratio. Yuanxin Zhou and P. K. Mallick Copyright © 2014 Yuanxin Zhou and P. K. Mallick. All rights reserved. Performance Evaluation of Glass-Epoxy-TiC Hybrid Composites Using Design of Experiment Sun, 09 Feb 2014 12:21:23 +0000 The present paper reports the processing and solid particle erosion behavior of a multiphase composite consisting of epoxy resin reinforced with E-glass fiber and TiC particles. The TiC powder synthesized from ilmenite employing DC extended thermal plasma technique has been used as the filler in these glass epoxy composites. It is observed that with increasing percentage of filler particles, there is significant improvement in hardness and erosion wear performance. It is also observed that, among all the factors, impact velocity is the most significant factor followed by TiC percentage and impingement angle, while erodent size has the least significance on erosion of the reinforced composite. Taguchi's orthogonal arrays have been used to identify the controlling factors influencing the erosion wear rate. Sangita Mohapatra, Sisir Mantry, and S. K. Singh Copyright © 2014 Sangita Mohapatra et al. All rights reserved. Effect of Coupling Agent on the Properties of Polymer/Date Pits Composites Thu, 09 Jan 2014 13:10:15 +0000 The morphology of the fracture surfaces of polymer/date pits composites was investigated. Polymers used in this study were high density polyethylene (HDPE) and polystyrene (PS). Date pits in the form of granules were two types of date pits: khlaas (K) and sekari (S). Two coupling agents, diphenylmethane-4 4′-diisocyanate (DPMI) and ethylene propylene grafted with malice anhydride (EP-g-MA), were used to ease the incorporation of date pit particles into polymer matrix. The SEM micrographs of the neat composites, that is, with no coupling agents, showed coarse morphology with bad dispersion, adhesion, and distribution of date pit particles within the polymer matrix. On the other hand, PS100/K composites coupled with DPMI and EP-g-MA had reasonable dispersed phase size with good distribution and adhesion to the composite matrix which in turn improve the mechanical properties of the resulted polymer/date pits composites. Fares D. Alsewailem and Yazeed A. Binkhder Copyright © 2014 Fares D. Alsewailem and Yazeed A. Binkhder. All rights reserved. Mechanical Properties of Polymer Concrete Sun, 29 Dec 2013 18:04:59 +0000 Polymer concrete was introduced in the late 1950s and became well known in the 1970s for its use in repair, thin overlays and floors, and precast components. Because of its properties like high compressive strength, fast curing, high specific strength, and resistance to chemical attacks polymer concrete has found application in very specialized domains. Simultaneously these materials have been used in machine construction also where the vibration damping property of polymer concrete has been exploited. This review deals with the efforts of various researchers in selection of ingredients, processing parameters, curing conditions, and their effects on the mechanical properties of the resulting material. Raman Bedi, Rakesh Chandra, and S. P. Singh Copyright © 2013 Raman Bedi et al. All rights reserved. Studies on Carbon-Fly Ash Composites with Chopped PANOX Fibers Mon, 23 Dec 2013 16:34:09 +0000 Chemical analysis and morphological studies of fly ash reveals the complex chemical constituents present as spherical particles with diameter of less than 25 μm. The constituents of fly ash are silica, alumina, iron oxide, titanium dioxide, calcium and magnesium oxide, and other trace elements. The use of thermosetting as well thermoplastic polymer matrix has been made by several workers to develop polymer matrix fly ash particulate composites by using the hard and abrasive properties of fly ash and lightweight of polymers. Such composites have poor mechanical strength, fracture toughness, and thermal stability. To overcome these shortcomings, in carbonaceous matrix, the carbon fibers were added as additional reinforcement along with the fly ash. The composites were developed with two different methods known as Dry method and Wet method. The processing parameters such as temperature and pressure were optimized in establishing the carbon matrix. Physical, thermal, and mechanical characteristics were studied. The microstructures of composites show good compatibility between fly ash and fibers with the carbon matrix. These composites have higher strength, thermal stability, and toughness as compared to polymer matrix fly ash particulate composites. Rakesh V. Patel and S. Manocha Copyright © 2013 Rakesh V. Patel and S. Manocha. All rights reserved. Buckling Analysis of Functionally Graded Material Plates Using Higher Order Shear Deformation Theory Mon, 23 Dec 2013 10:01:59 +0000 The prime aim of the present study is to present analytical formulations and solutions for the buckling analysis of simply supported functionally graded plates (FGPs) using higher order shear deformation theory (HSDT) without enforcing zero transverse shear stresses on the top and bottom surfaces of the plate. It does not require shear correction factors and transverse shear stresses vary parabolically across the thickness. Material properties of the plate are assumed to vary in the thickness direction according to a power law distribution in terms of the volume fractions of the constituents. The equations of motion and boundary conditions are derived using the principle of virtual work. Solutions are obtained for FGPs in closed-form using Navier’s technique. Comparison studies are performed to verify the validity of the present results from which it can be concluded that the proposed theory is accurate and efficient in predicting the buckling behavior of functionally graded plates. The effect of side-to-thickness ratio, aspect ratio, modulus ratio, the volume fraction exponent, and the loading conditions on the critical buckling load of FGPs is also investigated and discussed. B. Sidda Reddy, J. Suresh Kumar, C. Eswara Reddy, and K. Vijaya Kumar Reddy Copyright © 2013 B. Sidda Reddy et al. All rights reserved. Characterisation of Natural Fibre Reinforcements and Composites Wed, 18 Dec 2013 09:42:14 +0000 Recent EU directives (e.g., ELV and WEEE) have caused some rethinking of the life cycle implications of fibre reinforced polymer matrix composites. Man-made reinforcement fibres have significant ecological implications. One alternative is the use of natural fibres as reinforcements. The principal candidates are bast (plant stem) fibres with flax, hemp, and jute as the current front runners. The work presented here will consider the characterisation of jute fibres and their composites. A novel technique is proposed for the measurement of fibre density. The new rule of mixtures, extended for noncircular cross-section natural fibres, is shown to provide a sensible estimate for the experimentally measured elastic modulus of the composite. Richard K. Cullen, Mary Margaret Singh, and John Summerscales Copyright © 2013 Richard K. Cullen et al. All rights reserved. Internal-Notched Flexure Test for Measurement of Mode II Delamination Resistance of Fibre-Reinforced Polymers Tue, 10 Dec 2013 11:52:47 +0000 This paper introduces a new test, method, named internal-notched flexure (INF) test, that is designed to measure the critical energy release rate of fibre-reinforced polymers for delamination growth in shear mode (mode II). The INF test generates stable delamination growth, with a monotonic increase of load and displacement in a nearly linear fashion. Values of the mode II delamination toughness were deduced using experimental compliance fitting method. Good repeatability of the results was obtained. Compared with the end-notched flexure (ENF) test using the same material, the INF test yielded higher delamination resistance, possibly due to the bridging fibres found between fracture surfaces of the INF test specimens. Chengye Fan, P.-Y. Ben Jar, and J.-J. Roger Cheng Copyright © 2013 Chengye Fan et al. All rights reserved. Influence of SiC/Si3N4 Hybrid Nanoparticles on Polymer Tensile Properties Thu, 31 Oct 2013 18:37:18 +0000 Nanostructured silicon carbide (SiC)/silicon nitride (Si3N4) hybrid nanoparticles exhibit a high-potential for reinforcement of polymers. In the present investigation, silicon carbide (-SiC) nanoparticles (~30 nm) were sonochemically coated on acicular silicon nitride (~100 nm  nm) particles to increase the thermal and mechanical properties of Nylon-6 nanocomposite fibers. To produce Nylon-6/(SiC/Si3N4) nanocomposite fibers, we have followed a two-step process. In the first step, SiC nanoparticles were coated on Si3N4 nanorods using a sonochemical method and Cetyltrimethylammonium Bromide surfactant. In the second step, the SiC coated Si3N4 hybrid nanoparticles were blended with Nylon-6 polymer and extruded in the form of nanocomposite polymer fibers. The nanocomposite fibers were uniformly stretched and stabilized using a two-set Godet roll machine. The diameters of the extruded neat Nylon-6 and SiC/Si3N4/Nylon-6 nanocomposite fibers were measured using a scanning electron microscope and then tested for their tensile and thermal properties. These results were compared with the neat Nylon-6 polymer fibers. These results clearly indicate that the as-prepared nanocomposite polymer fibers are much higher in tensile strength (242%) and Young’s modulus (716%) as compared to the neat polymer fibers. Vijaya K. Rangari, M. Yousuf, and Shaik Jeelani Copyright © 2013 Vijaya K. Rangari et al. All rights reserved. Evaluation Effects of the Short- and Long-Term Freeze-Thaw Exposure on the Axial Behavior of Concrete-Filled Glass Fiber-Reinforced-Polymer Tubes Wed, 30 Oct 2013 13:19:25 +0000 Previous studies have demonstrated the high performance of the concrete-filled fiber-reinforced polymer (FRP) tubes (CFFTs) as a stay-in-place formwork and confining material for concrete structures. However, there are several concerns related to the behavior of CFFT as a protective jacket against harsh environmental effects. The environmental effects such as freeze-thaw cycles and deicing salt solutions may affect materials properties, which may affect the structural response of CFFT members as well. This paper presents the test results of experimental investigation on the durability of short- and long-term behaviors of CFFT members. Test variables included the effect of confining using GFRP tubes, freeze-thaw cycles exposure in salt water, and the number of freeze-thaw cycles. CFFT cylinders (150 × 300 mm) were prepared and exposed to 100 and 300 freeze-thaw cycles in salt water condition. Then, pure axial compression tests were conducted in order to evaluate the performance of specimens due to freeze-thaw exposure, by comparing the stress-strain behavior and their ultimate load capacities. Test results indicated that the confinement using CFFT technique significantly protected the concrete when subjected to freeze-thaw exposure. Hend El-Zefzafy, Hamdy M. Mohamed, and Radhouane Masmoudi Copyright © 2013 Hend El-Zefzafy et al. All rights reserved. Tribological Performance Optimization of Al-7.5% SiCp Composites Using the Taguchi Method and Grey Relational Analysis Wed, 18 Sep 2013 10:11:48 +0000 The present study considers an experimental study of tribological performance of Al-7.5% SiCp metal matrix composite and optimization of tribological testing parameters based on the Taguchi method coupled with grey relational analysis. A grey relational grade obtained from grey relational analysis is used as a performance index to study the behaviour of Al-7.5% SiCp MMC with respect to friction and wear characteristics. The tribological experiments are carried out by utilizing the combinations of tribological test parameters based on the L27 Taguchi orthogonal design with three test parameters, namely, load, speed, and time. The material Al-7.5% SiCp metal matrix composite is developed by reinforcing LM6 aluminium alloy with 7.5% (by weight) SiC particle of 400 mesh size (~37 μm) in an electric melting furnace. It is observed that sliding time has a significant contribution in controlling the friction and wear behaviour of Al-7.5% SiCp MMC. Furthermore, all the interactions between the parameters have significant influence on tribological performance. A confirmation test is also carried out to verify the accuracy of the results obtained through the optimization problem. In addition, a scanning electron microscopy (SEM) test is performed on the wear tracks to study the wear mechanism. Shouvik Ghosh, Prasanta Sahoo, and Goutam Sutradhar Copyright © 2013 Shouvik Ghosh et al. All rights reserved. Mechanical Property and Fracture Behavior of Al/Mg Composite Produced by Accumulative Roll Bonding Technique Thu, 01 Aug 2013 08:46:41 +0000 The Al/Mg laminated composite was fabricated by an accumulative roll bonding (ARB) technique using Al-1100 and Mg-AZ31 at 573 K. Tensile properties along rolling direction under different ARB cycles were evaluated at the ambient temperature. The tensile strength of the Al/Mg composite increased gradually till three ARB cycle and then decreased after the fourth ARB cycles. Scanning electron microscopy (SEM) was used to investigate the microstructure evolution and the failure mechanism. The Al/Mg interface with interface angles between 30° and 35° has minimum tensile strength. A higher or lower interface angle improves the tensile strength, and the interface angle can be reduced by increasing the number of cycles in the ARB process. Thus, the crack at the coarse intermetallic compounds and rupture of the Al layer after fourth cycle caused the premature failure of the specimens during the tensile test. Chih-Chun Hsieh, Ming-Che Chen, and Weite Wu Copyright © 2013 Chih-Chun Hsieh et al. All rights reserved. Effect of Natural Fillers on Mechanical Properties of GFRP Composites Mon, 08 Jul 2013 08:30:16 +0000 Fiber reinforced plastics (FRPs) have replaced conventional engineering materials in many areas, especially in the field of automobiles and household applications. With the increasing demand, various modifications are being incorporated in the conventional FRPs for specific applications in order to reduce costs and achieve the quality standards. The present research endeavor is an attempt to study the effect of natural fillers on the mechanical characteristics of FRPs. Rice husk, wheat husk, and coconut coir have been used as natural fillers in glass fiber reinforced plastics (GFRPs). In order to study the effect of matrix on the properties of GFRPs, polyester and epoxy resins have been used. It has been found that natural fillers provide better results in polyester-based composites. Amongst the natural fillers, in general, the composites with coconut coir have better mechanical properties as compared to the other fillers in glass/epoxy composites. Vikas Dhawan, Sehijpal Singh, and Inderdeep Singh Copyright © 2013 Vikas Dhawan et al. All rights reserved.