APEM jowatal Advances in Production Engineering & Management Volume 11 | Number 1 | March 2016 | pp 5-14 http://dx.doi.Org/10.14743/apem2016.1.205 ISSN 1854-6250 Journal home: apem-journal.org Original scientific paper Assessment of mechanical and wear properties of epoxy-based hybrid composites Agunsoye, J.O.a, Bello, S.A.ab- , Bello, L.a, Idehenre, M.M.a aDepartment of Metallurgical and Materials Engineering, University of Lagos, Akoka, Yaba, Lagos Nigeria bDepartment of Materials Science and Engineering, Kwara State, University, Malete, Kwara State Nigeria A B S T R A C T A R T I C L E I N F O Discarded florescent tubes and graphite rods obtained from dumped primary cells have been processed to obtain glass and graphite particles. 80 |m glass and graphite particles were used as reinforcements in epoxy resin, LY 556 cured with HY 931 hardener to produce epoxy resin hybrid composites. The morphology, mechanical properties, thermal stability and wear resistance characteristics of the epoxy resin glass/graphite hybrid composites were studied. The thermogravimetric analyser TGA 701 was used to examine the thermal stability of the epoxy resin glass particle/graphite composites. Addition of graphite and glass particles enhanced the strength, thermal stability and wear resistance of the epoxy resin. However, tensile strain and impact energy absorption of the epoxy resin hybrid composites started declining at 6 wt% of glass particle addition. The increase in wear rate of the composites with an increment in applied loads is attributable to increase in the normal reaction between the examined sample surfaces and the emery paper. Furthermore, the increase in wear resistance with an increment in wt% of glass particle additions is attributable to good interfacial adhesion between matrix and the fillers. The textural and appearance differences between the scanning electron micrographs of the control and epoxy resin hybrid composites is attributable to the presence of new phases due to exothermic and cross linking reaction between the matrix and the fillers. Hence, new vital engineering composites peculiar to automobile, aerospace and building industries have been produced. © 2016 PEI, University of Maribor. All rights reserved. Keywords: Epoxy resin Composite Glass particle Graphite particle Mechanical properties Wear properties Corresponding author: sefiu.bello@kwasu.edu.ng; adekunle_b@yahoo.com (Bello, S.A.) Article history: Received 11 June 2015 Revised 8 January 2016 Accepted 19 January 2016 1. Introduction Epoxy resins belong to a class of polymer under the aegis of thermoset [1]. They possess excellent mechanical strength, electrical and chemical resistance; good thermal characteristic and fine adhesion to many substrates after cure. They are used as matrix resins for reinforced composites, in aerospace industry, adhesives in car, as insulating materials for electrical and electronic industry. However, when compared to other light materials like aluminium, they have low mechanical strength and thermal resistance. Hence, filling of epoxy resin for improved mechanical, wear and thermal resistance properties is imperative. The mechanical performance of the fiber-reinforced composites usually depends on the properties of the matrix and fiber materials [2-4]. Reinforcement such as glass has good thermal resistance, wear resistance and high strength but they have low fracture toughness. Also, in the development of wide variety of composites for application in areas such as aerospace industry, automobile industries and sporting goods, carbon fiber has been used as the reinforcing material [5-6]. Carbon fibre reinforced polymer com- 5 Agunsoye, Bello, Bello, Idehenre posites are being used in a wide range of engineering applications because of increase in the impact energy absorption per unit weight, reduce noise and vibrations and excellent resistance to fatigue [7]. Hybridization of particles as a filler for a polymer gives rise to a new polymer based composite with enhanced mechanical properties [8]. Hence, the composites of these three engineering materials, i.e. polymer-matrix composites with small amount and size of glass and carbon particle reinforcements, could improve strength and impact energy of the composites. This is the thrust of this research i.e. to use the good properties offered by both glass and carbon particles to reinforce epoxy resin to develop composites with improved properties. Such composites made from high-performance particles (e.g., carbon and glass particles) embedded in compliant polymeric resins can be used in a wide range of fields such as aerospace engineering and sports utilities. The developed composites are expected to have high specific strength and toughness, superior manufacturability, as well as excellent corrosion resistance and fatigue tolerance. Agunsoye et al. (2014) worked on the development and characterization of aluminium dross/epoxy resin composite materials [9]. Their results revealed that additions of particulate aluminium dross to epoxy resin enhanced significantly, the thermal and wear resistance of the epoxy resin aluminium dross composites. Hassan et al. (2012) worked on development of polyester/eggshell particulate composites [10]. Their results show that the addition of eggshell to the polyester slightly improved the mechanical properties of the produced composites. Allaouis et al. (2002) fabricated and studied mechanical and electrical properties of epoxy resin/carbon nanotube composites [11]. Results of the experimental examination revealed that the Young's modulus and the yield strength of the composites have been doubled and quadrupled for composites with respectively 1 wt% and 4 wt% nanotubes, compared to the pure resin matrix samples. Conductivity measurements on the composite samples showed that the insulator-to-conductor transition took place for nanotube concentration between 0.5 wt% and 1 wt%. Vala-sek et al. 2015 studied two-body abrasive wear of polymeric composites using waste abrasive Al2O3 particles as a filler [12]. Their results indicated 16 % improvement in hardness with composite made from 284 [im sized Al2O3 particles. Many worked have been focused on enhancement of thermoset properties, the use of flo-rescent tube glass particles and graphite particles obtained from discarded primary cell as reinforcements in epoxy is rare or not found. However, in this work, thermoset hybrid composites have been produced from epoxy resin (LY 556) reinforced with 80 [im glass and graphite particles. The mechanical properties, wear behaviour, phase morphology and distribution in the epoxy matrix of the produced composites were investigated. The glass particles used were obtained from processed discarded fluorescent tubes which have the potential of causing serious environmental harm due to mercury. The mercury from just one fluorescent tube is enough to pollute 30,000 l of underground water so that the water is no longer safe to drink [13]. Hence, this research was also aimed at eliminating this challenge by making use of this potential harmful material (discarded fluorescent tube) as reinforcement in the production of composites for engineering applications. 2. Materials and methodology Materials used in this work are discarded florescent tube procured from Waste Dumping Centre of University of Lagos; graphite rods were obtained from discarded primary cells. Epoxy resin (LY 556), HY931 hardener and distilled water were purchased from Tony Nigeria Chemicals, Ojota Lagos. The major equipment used includes scanning electron microscope (SEM), Instron extensometer, model 3319; hot press, X-ray diffractometer and Avery Denison Universal Impact Testing Machine. Broken glasses obtained from florescent tubes were submerged in a 100 l of boiling water contained in a plastic drum covered with 0.5 kg ground sulphur powder. This attempt was made to remove mercury from the florescent tube. The resulted suspension containing black particles was decanted off the drum after 24 h, leaving behind the broken glasses. The broken glasses were sundried at average daily temperature of 25 °C for 2 days. They were ground into powder using 87002 LIMOGES planetary ball mill, model 28A20 92 in accordance with [14]. Glass pow- 6 Advances in Production Engineering & Management 11(1) 2016 Assessment of mechanical and wear properties of epoxy-based hybrid composites ders were classified using a set of sieves arranged in descending order of mesh sizes ranging from 50-300^m. Sieves were vibrated for 30 min using a sine shaker. Solid graphite electrodes were ground and sieved. Fig. 1 and Fig. 2 present glass and graphite particles. Epoxy resin (LY 556) and hardener (HY 931) were mixed inside a beaker at 3:1 in accordance with manufacturer specification. The mixture was stirred by a hot plate and stirrer, model Jen-way 1000 at 120 °C for 1 h and then poured into a metallic mould coated with petroleum jelly. Epoxy resin/hardener blends were left in the mould for 2 days at room temperature to obtain epoxy/hardener preforms. Epoxy preforms were placed in a mould with different cavities patterned to the standard shapes for mechanical property analyses. The preforms were heated to 150 °C, held at the temperature for 1 h and then forged to obtain the standard samples for analyses (in accordance with ASTM D 3039 M959 and ASTM D 790-90), using a hot press. For composite production, a mixture containing 80 [im sized graphite and glass particles were dispersed in 50 cm3 of water in a beaker and then stirred manually with a glass rod for a period of 10 min. The mixture was added to 250 cm3 epoxy resin (LY 556) in another beaker and then stirred for 15 min. 30 % HY931 hardener was added to the epoxy resin/filler mixture. The resulting mixture was stirred using magnetic mantle shaker for 1 h at a temperature of 120 °C to evaporate water molecules. The epoxy resin mixture was poured into a mild steel mould (coated with petroleum jelly as a dispatching/releasing agent) and then left in the mould for 2 days at room temperature. Epoxy graphite/glass particles hybrid composite preforms were placed in a forming mould. They were heated to 150 °C, held at the temperature for 1 h and then forged to obtain standard samples for mechanical property investigation. Six different composite samples produced contained 2 wt% graphite particles with increasing wt% of glass particles from 2-12 % at 2 % interval. Phase identification of the produced epoxy samples were carried out using a Panalyti-cal Empyrean X- ray diffractometer (XRD) in accordance with [15]. Morphology of the samples was examined with the aids of scanning electron microscope, ASPEX 3020 in line with [16]. Tensile samples of 80 mm gauge length and 7 mm width were subjected to tensile test using Instron extensometer, model 3369. Samples were gradually loaded at a strain rate of 103 1/s [17]. This resulted in the simultaneous elongation and reduction in the cross section of the sample until the samples became fractured. The flexural test was carried out on the bended 100 mm square samples. The samples were loaded at the bended centre point until fracture occurred at the point. 150 mm diameter samples were subjected to compressive load using Instron exten-someter. The impact energies of the produced samples were determined with the aids of Avery Den-ison Universal Impact Testing Machine. The notched 60 x 10 x 10 mm3 dimensioned samples were subjected to the Charpy impact test. First, the hammer pendulum was released to set the scale to zero point. Each sample was impacted with hammer pendulum of weight 300 J, released from the upper position of the machine. The impact energy absorbed by each sample was read and then recorded. Fig. 1 Photograph of glass particles Fig. 2 Photograph of graphite particles Advances in Production Engineering & Management 11(1) 2016 7 Agunsoye, Bello, Bello, Idehenre The wear resistance of 60 x 10 x 10 mm3 dimensioned samples of the control, epoxy resin hybrid composites containing 2, 4 and 12 % glass particles were investigated using Pin on Disc wear machine. Densities and the initial masses of the examined samples are expressed in two Cartesian system as follows (1.33 g/cm3, 8 g); (1.28 g/cm3, 7.7 g); (1.27 g/cm3, 7.64 g) and (1.24 g/cm3, 7.43 g) respectively. The wear test was carried out on a 200 mm circular rotating disc with attached emery paper of 220 grit size according to [2]. The surface of the test sample was placed against the rotating disc for a period of 60 s under different loads at a speed of 2.36 m/s. The final mass after each test was measured and recorded. The mass loss during the investigation was calculated and recorded using the Eq. 1. The thermal stability of the control and the epoxy resin hybrid composites containing 2 and 12 % glass particles were examined using TGA 701. Each sample was heated from room temperature to a maximum of 900 °C for 200 min. The thermal stability was studied as a function of weight loss with heating temperature and time. 3. Results and discussion 3.1 X-ray diffractograms X-ray diffractogram in Fig. 3 reveals the phases present in the epoxy resin (control) sample. It was observed from the result obtained that aluminium manganese titanium (Al3Ti0.78Mn0.25), burnt lime (CaO), pyrolusite (P2O5), sodium aluminium sulphide (Na4AlS5) were identified at diffraction angles of 44.23°, 46.24°, 27.81° and 14.02° respectively. Fig. 4 shows the X-Ray diffractogram of the epoxy resin hybrid composite containing 12 % glass particles. There are two peaks with many shoulders at their sides. This indicates higher degree of phase segregation and or straining within the matrix. They are attributable to chemical interaction among epoxy resin, glass and graphite particles. It was observed from the result that the phases were Iron titanium (FeTi), anatase (TiO2), Titanium Zinc (Zn0.6Ti0.4X These phases were identified at diffraction angles of 50.01°, 28.23° and 85.23° respectively. Mass loss = initial mass - final mass (1) C o 0 0 0 5 0 0 2 0 3 0 5 0 7 0 Position [°2Theta] Fig. 3 X-ray diffractogram of the unfilled epoxy resin [2] 8 Advances in Production Engineering & Management 11(1) 2016 Assessment of mechanical and wear properties of epoxy-based hybrid composites 3.2 SEM micrographs Microstructure of epoxy resin control sample is presented in Fig. 5. The structure reveals the white phases within the black matrix. The white phases are attributable to Al3Ti0.7sMn0.25, CaO and Na4AlS5 as indicated by the diffractogram in Fig. 3. Fig. 6 presents the microstructure of the filled epoxy resin. The facial difference of the microstructure in Fig. 7 from that in Fig. 6 is attributable to glass and graphite particle additions. The microstructure appears rocky which indicates a good interfacial adhesion between the matrix and reinforcements. Fig. 5 Unfilled epoxy resin SEM microgragh Fig. 6 Epoxy resin hybrid composite micrograph obtained from SEM Advances in Production Engineering & Management 11(1) 2016 9 Agunsoye, Bello, Bello, Idehenre 3.3 Mechanical properties It was observed from Fig. 7, Fig. 8, and Fig. 9 that filling of epoxy resin with graphite and glass particles produced epoxy resin hybrid composites with enhanced tensile, flexural and compressive strengths. Strength of the epoxy hybrid composites increased with an increment in wt% of glass particle additions up to 10 wt% when the ultimate tensile and flexural strength start declining. This indicated epoxy resin saturation level. However, the increase in compressive strength beyond 10 wt% of glass particles may be attributable to brittleness of the phases within the matrix which enhance the strength in compression. Fig. 10 and Fig. 11 depicted that impact energy and tensile strain started declining at 6 wt% glass particle addition. This indicated a critical glass filling level such that glass particle addition above this level embrittled the epoxy hybrid composites. The decline in impact energy and tensile strain could be associated with brit-tleness of glass and graphite particles. During loading, the hybridized particles allowed the crack propagation in a more rapid manner than that in the case of epoxy hybrid composites at lower wt% of glass particle additions. This caused the 2 % graphite-6 % glass particle epoxy composites to fail at lower absorbed energy and percentage elongation. 70 145 r 40 5 10 %wt of glass particles 15 115 0 5 10 %wt of glass particle addition 15 Fig. 7 Ultimate tensile with wt% of glass particles 160 Q- H e eu +J m cu > t/3 m cu u a o u 150 140 130 120 s