Mechanics, Materials Science & Engineering, July 2017 – ISSN 2412-5954
Stress Stability of Aluminium-Glass Composites 1 Abodunrin O.W.1, Alo F.I.2 1 – Department of Physics, Joseph Ayo Babalola University, Osun State, Nigeria 2 – Department of Material Science and Engineering, O.A.U, Ife, Osun state, Nigeria a – tayoabodunrin@yahoo.com b – iretispecial2005@yahoo.com DOI 10.2412/mmse.61.28.957 provided by Seo4U.link
Keywords: pressure, particle size, ductility, fracture toughness, stable stress, max. compressive stress, yield point and structural stability.
ABSTRACT. The effects of compaction pressure and particle size on the mechanical property of Aluminium-Glass based samples are reported in this study. The samples were of cross sectional area 34.0 x35.0 mm2 with varying thickness 20.8 22.10 mm. Particle size of 26.5nm was used for both Aluminium and Glass. The samples were made into solids by pressing the materials together at constant pressure of 300bars. Results showed that composition of Aluminium in Glass, compaction pressure and particle size greatly influenced the stress/time relationship of the samples. With the particle size, it was revealed that samples were found with stress stability between 5 - 70% weights of Aluminium in the composites. The sample was noted to have maximum strength for 30 % weight of Aluminium in composites in the compression test analyses.
Introduction. Stress stability is the ability of a body or system to return to a previously established steady state, after being perturbed. Besides, it is also the ability of a body to regain balance at the moment of giving it any distortion. Stress stability of a molded material could also imply an increase in stress which corresponds to an equal increase in time. In such compacted material, the stress / time relationship did not accommodate points of fracture and rupture up to the yield point [1, 2]. Stress stability is a mechanical quantity which was usually measured from compressive strength of the material. It was determined from observation of the stress – time relationship of a material. The higher the stress a material could withstand, the higher was its resistance to fracture. The fracture toughness was thus improved from contribution of stress stability and the maximum compressive strength of the material. A fracture is the propagation of micro cracks / cracks within certain regions of the material under the action of high / residual stress developed in the sample. A point of fracture of the material is a point on the stress-time curve where the sample experiences separation into parts as a result of close and diverse fractures within certain regions of the material under the action of increasing load in compression test. The yield point is a point on stress-time curve above the proportionality region where sudden increase of a unit stress does not have corresponding unit increase in time. The toughness of a material signifies the ability of a material to absorb energy without causing breakage. This implies that Metallic-Glass had the capability to absorb much energy before or at point of breakage of the samples up to the yield point [3]. The choice of Aluminium is as a result of its ductility and strength used in diverse areas. Fracture toughness is the ability of the material to resist crack propagation in the material. Ductility is defined as the ability of a material to undergo appreciable plastic deformation before fracture. Glass had low ductility [4, 5] and the need for reinforcement of a material of high ductility, structural stability was considered to increase the level at which breakage may be experienced during impact or compression test [6, 7]. 1
© 2017 The Authors. Published by Magnolithe GmbH. This is an open access article under the CC BY-NC-ND license http://creativecommons.org/licenses/by-nc-nd/4.0/
MMSE Journal. Open Access www.mmse.xyz
Mechanics, Materials Science & Engineering, July 2017 – ISSN 2412-5954
Much is yet to be done in the direction of stress stability by combining metallic elements with Glass to form composites. Therefore, attention in this study is geared towards determining the stress stability at constant pressure and same particle sizes. Moreover, Aluminium-Glass composites were proposed for industrial and domestic purposes. Experimental procedure The materials used for the study include Aluminium powder of purity of 95.50% purity, sodium silicate powder of purity 99.50% both of particle sizes of 26.5nm obtained from British drug House (BDH), England. The specimen slide was boiled in cromic acid and agitated in trioxoethelene for 20 minutes to remove unwanted attachment on the surface of slides. Glass powder of particle size of 26.5nm which had earlier been crushed and pulverized before sieving with a mechanical mesh from mechanical section at Centre for Energy Research and Development (CERD) in Obafemi Awolowo University, Ile-Ife, Nigeria was used. Weighing was done with digital weighing balance (Model, BT 200) of sensitivity 0.001g. Sodium silicate liquid was prepared by mixing distilled warm water at 800C with sodium silicate powder in ratio 1:3. A manually operated press capable of producing one composite at a time with an average thickness of 21.5mm and cross sectional area of 1156mm2 was used for molding the samples at Engineering Geology Laboratory at Federal University of Technology, Akure. Formula for mixing in percentage is AlxGlass100-x x= 5.0, 10.0, 15.0, 20.0…100.0.The Aluminium and Glass powders in grams were mixed together in 20 different ratios at 300 bars. Sodium silicate liquid added was between 12.5-14.5 % of Al-Glass Mixture. The mixing was carried out manually in a closed container. The samples were subjected to same moisture condition for four weeks in an open atmosphere in the laboratory. Samples were measured with compressive test machine from CERD. Results Table 1. Compressive test values of samples at room temperature (27⁰C), 300 bars, 26.5 nm particle size and area of 1190 mm2. % wt (Al/Glass)
Thickness
Maximum Compressive stress(MPa)
(mm)
0.00/100.0
22.10
32.12
5.00/95.0
21.90
40.24
10.0/90.0
21.70
43.94
15.0/85.0
21.50
45.53
20.0/80.0
21.40
47.86
25.0/75.0
21.30
48.77
30.0/70.0
21.25
57.03
35.0/65.0
21.20
42.27
40.0/60.0
21.20
41.45
45.0/55.0
21.15
40.98
50.0/50.0
21.10
36.09
55.0/45.0
20.95
35.46
MMSE Journal. Open Access www.mmse.xyz
Mechanics, Materials Science & Engineering, July 2017 – ISSN 2412-5954
60.0/40.0
20.80
30.01
65.0/35.0
20.75
28.54
70.0/30.0
20.73
26.56
75.0/25.0
20.73
22.60
80.0/20.0
20.60
9.17
85.0/15.0
20.60
6.60
90.0/10.0
20.50
5.60
95.0/5.00
20.35
5.06
100.0/0.00
20.28
4.06
60
stress ( Mpa)
50 40 30 20 10 0 0
20
40
60
80
100
120
% weight of Al
Fig. 1. Variation of Stress with % Weight of Al at 300 bars and 26.5nm.
60
Compress Stress (MPa)
50 40 30 20 10 0 20
20.5
21
21.5
22
Thickness (mm)
Fig. 2. Variation of Compressive Stress with Thickness at 300 bars and 26.5 nm. MMSE Journal. Open Access www.mmse.xyz
22.5
Mechanics, Materials Science & Engineering, July 2017 – ISSN 2412-5954
Maximum compressive Stress(Mpa)
60 m
m
50
m
b
m
40
b
30 20 10 0 0
20
40
60
80
-10
100
120
140
160
180
Time (seconds)
Al5Glass95
Al10Glass90
Al15Glass85
Al20Glass80
Al25Glass75
Fig. 3. Compressive Stress versus Time from 5 to 25 % wt. of Al for 300 bars and 26.5 nm, m is the point of maximum compressive stress.
Maximum Compressive Stress (Mpa)
60
m
50 b
m
40
m b b
30 20 10 0 0
20
40
-10
60
80
100
120
Time(seconds) Al30Glass70
Al40Glass60
Al45Glass55
Fig. 4. Compressive Stress versus Time from 30 to 45 % wt. of Al for 300 bars and 26.5 nm, m = max compressive stress, b = point of breakage.
MMSE Journal. Open Access www.mmse.xyz
Mechanics, Materials Science & Engineering, July 2017 – ISSN 2412-5954
Maximum Compressive Stress (Mpa)
40 35 30
25 20 15 10 5 0 -5
0
0.5
1
Al50Glass50
1.5
Al55Glass45
2 2.5 Time (seconds Al60Glass40
3
3.5
4
Al65Glass35
4.5
Al70Glass30
Maximum Compressive Stress(MPa)
Fig. 5. Compressive Stress with Time for samples from 50 to 70 % wt. of Al, pressure of 300 bars and 26.5 nm particle size (m = max compressive stress, b = point of breakage).
25 20 15 10 5 0
0
5
10
-5
15
20
25
30
Time (seconds) Al75Glass25
Al80Glass20
Al90Glass10
Al100Glass0
Al85Glass15
Fig. 6. Compressive Stress versus Time (from 75 to 100 % wt. of Al for 300 bars and 26.5 nm). Discussion Compressive Stress of the Samples of Al-Glass. In Table 1 the stress has highest value for 30 % weights of Aluminium in the composites of 300 bars. As for the lowest values, stress was noted at 100 % weight of Aluminium in the composites. Compressive Stress with Thickness of the Samples of Al-Glass. The stress with % weight of Aluminium was in reverse direction to that of stress-thickness relationship in Figures 1 and 2. The thickness and stress have maxima at 0 and 30 % weight of Aluminium. Stress, Time, Strength and Stress Stability of Al-Glass Composites. Figures 3 – 6 displayed a pressure value of 300 bars and 26.5 nm particle size whereby the stress – time relationships were MMSE Journal. Open Access www.mmse.xyz
Mechanics, Materials Science & Engineering, July 2017 – ISSN 2412-5954
found to be stable over specified ranges which are indications that the material has the tendency of being stress stable. Figure 3 displayed the variation of stress – time for Al5Glass95, Al10Glass90, Al15Glass85, Al20Glass80 and Al25Glass75 of 26.5 nm particle sizes. The results showed that as the time increases the stress increased gradually without rupture along each of the curves. The increase in strain - time became noticeable for these composites without fracture along the curves. All these samples were classified as being stress stable. The variation of stress - time for samples Al30Glass70, Al35Glass65, Al40Glass60 and Al45Glass55 at 26.5 nm particle sizes are shown in Figure 4. The results depicted gradual increase in stress - time along the curve with no ruptures up to the point of breakage. These are indications of stress stability of the materials just before the point of breakage. It should be noted that samples that contain points of rupture and fracture did not have stress stability. For a sample to have stress stability, it must not exhibit the above mentioned flaws. In other words, the sample with stress stability must display gradual increase in stress with corresponding equal increase in time. The point of breakage did not necessarily coincide with the maximum compressive stress which was found in the samples observed. Stress stabilities were observed in Figure 5 for samples Al50Glass50 Al55Glass45Al60Glass740Al65Glass35 and Al70Glass30 as an increase in stress corresponds to equal increase in time. The figure also revealed that the samples at 26.5 nm have no point of fracture or rupture over the entire range. The stress-time curves for the samples increased gradually from the origin to maximum values up to the yield point. The samples have different ranges of values for stability in the region of stress stability. There was an improvement in the composites considered from ordinary glass, whose maximum compressive stress was 30.32 MPa to Al-Glass composite which maximum compressive stress was 57.03 MPa at particle size 26.5 nm. The implication of this was that a new composite that could with stand stress up to 57.03 MPa was obtained. The sample that could with stand minimum stress was Al100Glass0 while that for maximum stress it was Al30Glass70. Figure 6 reflected the variation of compressive stress versus time for samples Al75Glass25, Al80Glass20, Al85Glass15, Al90Glass10 and Al100Glass0 at 26.5 nm particle sizes. The results revealed that all of these samples have points of fracture or rupture along the curves which implied they are not candidates of stress stability. In addition, Al75Glass25 has a zig-zag nature of stress - time which was an indication that the sample was also without stress stability. Summary. The combination of Al with other metal had been noted to generate improve performance in various device applications and utilization. Therefore, the mechanical properties of Glass could be adjusted for suitable application and utilization with appropriate reinforcement of Al in Glass. Improved compressive strength of Glass to 57.03 MPa was obtained while stress stabilities were observed from 5-70 % weight of Aluminium in composites at 26.5 nm particle size. The material could also be useful for decoration and other house hold aesthetics. Having examined the improved strength of the material, it is recommended the Al-Glass be used as pharmaceutical packaging material, aerospace and automobile industries. References [1] David, R. (2001). Stress-Strain Curves, Department of Materials Science and Engineering Massachusetts Institute of Technology, Cambridge, 1-14. [2] Nicholas, J. H. (2010). Dynamic Stability of Structures, proceedings of International Conference, 7-41. [3] Shantanu, V. M. (2015). Toughness of Bulk Metallic Glasses, Journal of Metals, Review, 5, 12791305. MMSE Journal. Open Access www.mmse.xyz
Mechanics, Materials Science & Engineering, July 2017 – ISSN 2412-5954
[4] Yoldas, B. E. (1975). Monolithic Glass Formation by Chemical Polymerization, Journal of Material Science, 10, 1856. [5] Chantikul, P., Anstis, G.R., Lawn, B.R. and Marshall, D.B. (1981). A Critical Evaluation of Indentation Techniques for Measuring Fracture Toughness II Strength Method.J. Am. Ceram. Soc., 64(9): 539-543. [6]Wachtman. J. B. (1996). Mechanical and Optical Properties of Ceramics. John Wiley & Sons. [7] Abodunrin O.W. and Oluyamo S.S. (2017). Structural Stability of Nano Crystalline Al-Glass Composites. International Organization of Scientific Research (IOSR) Journal of Applied Physics, 9 (1), 96-99.
MMSE Journal. Open Access www.mmse.xyz