Glass Fiber and Blast Furnace Slag Particles Reinforced Epoxy-based Hybrid Composites

Transcription

1 Glass Fiber and Blast Furnace Slag Particles Reinforced Epoxy-based Hybrid Composites Glass Fiber and Blast Furnace Slag Particles Reinforced Epoxy-based Hybrid Composites Prasanta Kumar Padhi * and Alok Satapathy Department of Mechanical Engg, National Institute of Technology, Rourkela , India Received: 24 September 2012, Accepted: 4 January 2013 Summary Blast furnace slag particles (BFSP), generated in large quantities during steel manufacture consist of SiO 2 and Al 2 O 3. This study indicates that glass fiber (GF) and blast furnace slag particles (BFSP) reinforced epoxy based hybrid composites processed by hand lay-up technique exhibit improved hardness, acceptable density and well dispersed reinforcer morphology. This work highlights preparation of value added polymeric composites for tribological applications by utilizing steel plant waste. Keywords: Blast furnace slag particles, Epoxy, Glass fiber, Composite, Hardness, Density, SEM Introduction Fibre-reinforced polymer composites are emerging as engineering materials with light weight, high mechanical properties, design flexibility and ease of fabrication; and are also offering applications in transport, aircraft, automobiles, aersopace, off-shore and on-shore structures, and also in commodity applications like, sports and electronics. In fiber reinforced polymer composites, reinforcing high modulus and high strengfth fibers serve as the principal load-carrying members; polymeric matrix binds the fibers and also transfers load to the fibers. In a fiber reinforced polymer composite, fibers and matrix retain their identities and provide synergistic properties, that cannot be achieved with either of the constituents acting alone. Possibility to tailor * Corresponding author s prasantakumar.padhi@sailrsp.co.in Smithers Rapra Technology, 2013 Applied Polymer Composites, Vol. 1, No. 2,

2 Prasanta Kumar Padhi and Alok Satapathy the mechanical properties of the composites through the control of fiber and matrix combinations and the selection of processing techniques makes fiber reinforced polymer composites very versatile. The most commonly used reinforcing fibers for polymeric composites are, carbon, glass, and aramid fibers; and also ceramic fibers like alumina, silicon carbide (SiC), mullite, and silicon nitride etc. for thermoset matrix composites; and natural fibers like, jute, sisal, etc for thermoplastic composites. The range of reinforced polymer composites includes, particulate composites, randomly oriented chopped short fiber reinforced polymeric composites, and also, unidirectional, cross ply, or angle ply geometry based continuous fiber reinforced polymeric composites. A judicious selection of matrix and the reinforcing phase can lead to a composite with a combination of strength and modulus comparable to, or even better than, that of a metallic material [1]. The improved performance of particle or filler reinforced polymeric composites is exhibiting great promise and potential for industrial and structural applications, along with low price based techno-economic advantages; and is a subject of considerable interest [2, 3]. This work investigates hybrid composites, where both fiber and particles have been used as reinforcers for a thermoset matrix. It has been proposed that by incorporating filler particles, or particulate reinforcers, along with continuous fibers, synergistic effects may be achieved with good mechanical and thermal properties [4, 5]. Blast furnace slag (BFS) particles are being generated in large quantities by steel plants, but the reinforcing potential of blast furnace slag particles for polymeric composite materials has not been explored. This work evaluates the potential of BFS particles, collected from the Rourkela Steel Plant (RSP of the Steel Authority of India Ltd.) as a reinforcing material for polymeric composites by developing glass fiber (GF) and blast furnace slag particles (BFSP) reinforced epoxy based hybrid composites processed by hand layup technique. Materials Bisphenol-A-Diglycidyl-Ether Epoxy LY 556, of 3.42 GPa modulus and 1100 kg/ m 3 density, chemically belonging to the epoxide family used as the matrix material, and HY951 used as hardener, were obtained from Ciba Geigy India Ltd. Reinforcing E-glass fibers of 72.5 GPa modulus and 2590 kg/m 3 density (360 roving) were obtained from Saint Gobian Ltd. Blast furnace slag particles (BFSP), used as particulate reinforcer, were obtained from Rourkela Steel Plant of Steel Authority of India Ltd., Rourkela, India. BFSP mainly consists of inorganic constituents such as silica (30-37 wt%), calcium oxide (28-37 wt%), 86 Applied Polymer Composites, Vol. 1, No. 2, 2013

3 Glass Fiber and Blast Furnace Slag Particles Reinforced Epoxy-based Hybrid Composites magnesium oxide (1-11 wt%) Al 2 O 3 (10-12 wt%) and Fe 2 O 3 (1 wt%) etc. Their bulk density varies in the range of kg/m 3. BFSP were grounded and sieved to µm. Experimental Composite Processing The low temperature curing epoxy resin (LY 556) and corresponding hardener (HY951) were mixed in a ratio of 10:1 by weight as recommended, and BFS particles were mixed with epoxy resin. Glass fiber reinforced epoxy matrix containing BFS particles with 40% fiber loading were processed by Hand Lay Up process. Testing and Characterization Density of the processed composite was evaluated by water-immersion technique. Micro-hardness measurement was performed using a Leitz microhardness tester. A diamond indenter, in the form of a right pyramid with a square base and an angle 136 between opposite faces, is forced into the material under a load of N. Tensile and flexural properties of the composite were evaluated on a universal testing machine (UTM Instron 1195) following the ASTM D 3039 and ASTM D 790 Standards respectively. Morphology of composites have been examined by Scanning Electron Microscope (JEOL JSM-6480LV) by mounting samples on stubs with silver paste. To enhance the conductivity of the samples, a thin film of platinum is vacuum-evaporated onto them before the photomicrographs were taken. Results and Discussions Density The composite under this investigation consists of three components, namely, matrix, fiber, and particulate filler. The theoretical density of composites in terms of weight fraction has been obtained as per the following equation [6] : ρ ct = 1 ( W f / ρ f ) + ( W m / ρ m ) + ( W p / ρ p ) (1) Applied Polymer Composites, Vol. 1, No. 2,

4 Prasanta Kumar Padhi and Alok Satapathy where, W and ρ represent the weight fraction and density respectively; and the subscript f, m, p and ct represent fiber, matrix, particulates and the composite materials respectively. The actual density ρ ce of the composite, however, can be determined experimentally by simple water-immersion technique. The volume fraction of voids V v in the composites is calculated using the following equation: V v = ρ ct ρ ce ρ ct (2) The theoretical and measured densities of the composites along with the corresponding volume fraction of voids are presented in Table 1. Composite density values calculated theoretically from weight fractions using the equation (1) are not equal to the experimentally measured values, and the difference is a measure of voids and pores present in the composites. With the increase in BFSP content from 10% to 20% in the composites like BE 1, and BE 2, the volume fractions of voids increases (although <5%) in comparison to 0 wt% filler, i.e. matrix in BE 0. Density of a composite depends on the relative proportion of matrix and the reinforcer. Difference between the theoretical density, and the calculated density depends on void content. Voids adversely affect some of the mechanical properties and also the performance of a composite. Higher void content adversely affects the properties of the composite [6]. A good composite should have fewer voids, however, the presence of voids is unavoidable in composite processed by hand-lay-up. Table 1. Experimental and theoretical densities of the composites Sample BFS content (wt%) Measured density (gm/cc) Theoretical density (gm/cc) Void fraction (%) Matrix (BE 0 ) Composite with 10% BFSP (BE 1 ) Composite with 20% BFSP (BE 2 ) Hardness The hardness of composites are measured in Leitz micro-hardness tester in vicker s hardness unit, which is then converted to MPa units. The variation of composite micro-hardness with the weight fraction of BFS content is shown in Figure 1 and Table 2. As shown in the Figure 1, in accordance with basic principles [7], the micro-hardness of composites increases with increasing BFS particles in the epoxy glass fibre composite. The hardness of the BE 1 88 Applied Polymer Composites, Vol. 1, No. 2, 2013

5 Glass Fiber and Blast Furnace Slag Particles Reinforced Epoxy-based Hybrid Composites Table 2. Hardness, tensile strength and flexural strength of the composites Sample Hardness (MPa) Tensile Strength (MPa) Flexural Strength (MPa) Matrix (BE 0 ) Composite with 10% BFSP (BE 1 ) Composite with 20% BFSP (BE 2 ) Figure 1. Variation of composite micro-hardness with filler (BFS) content composite with 10% BFSP is MPa, that is 33.7% higher than that of the matrix; and the hardness of the BE 2 composite with 20% BFSP is MPa, that is 52% higher than that of the matrix. Tensile and Flexural Properties As shown in Table 2, and in the Figures 2 and 3, the tensile strength and flexural strength of the composites reduces with increasing BFS particulate filler content. The tensile strength of the glass reinforced epoxy BE 0 gradually decreases from almost 343 MPa to almost 253 MPa and to 145 MPa with the formation of BE 1 and BE 2 composite with BFS particles. The flexural strength of the glass reinforced epoxy BE 0 gradually decreases from almost 417 MPa to almost 386 MPa and to 325 MPa with the formation of BE 1 and Applied Polymer Composites, Vol. 1, No. 2,

6 Prasanta Kumar Padhi and Alok Satapathy BE 2 composite. The decrease in tensile and flexural strength is probably due to lack of proper load or stress transfer from matrix to reinforcer. Figure 2. Variation of composite tensile strength with filler (BFS) content Figure 3. Variation of composite flexural strength with filler (BFS) content Morphology The scanning electron micrographs of the surfaces and cross-sections of the BFS particulate reinforcer and composite samples indicate morphology of BFS particles (Figure 4a), uniform distribution of reinforcers (Figure 4b), and good bonding between fiber and matrix (Figure 4c-d) during bending and fiber fracture. 90 Applied Polymer Composites, Vol. 1, No. 2, 2013

7 Glass Fiber and Blast Furnace Slag Particles Reinforced Epoxy-based Hybrid Composites (a) (b) (c) (d) Figure 4. SEM Micrographs of (a) raw blast furnace slag particles (b) a typical BFS filled glass epoxy composite surface (c) composite specimen subjected to bending (d) fiber fracture during bending Conclusions Blast furnace slag particles (BFSP), generated in large quantities during steel manufacture, consisting of SiO 2 and Al 2 O 3, have been used to develop glass fiber (GF) and blast furnace slag particles (BFSP) reinforced epoxy based hybrid composites by hand lay-up. The composites exhibit improved hardness, acceptable density and well dispersed reinforcer morphology. This work highlights preparation of value added polymeric composites for tribological applications by utilizing steel plant waste. Acknowledgements The authors acknowledge the support/sponsorship of the Steel Authority of India Ltd. (Rourkela Steel Plant) and the National Institute of Technology, Rourkela. Applied Polymer Composites, Vol. 1, No. 2,

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