სამეცნიერო და სასწავლო-სამეცნიერო სტატიები შესრულებული სტუ ფიზიკის დეპარტამენტის თანამშრომლების და სტუდენტების მიერ.

Study of the Carbon Composites in the Various Applications

Teimuraz Chichua, Temur Chichua, Aleksandre Toidze, Nikoloz Minashvili.

 Georgian Technical University and Tbilisi 199th Komarovi School. 

The work supported by a grant from the Rustaveli Fundation.

Abstract

The carbon composite materials are widely used as construction materials in the different industries such as aerospace, military or in the civil engineering. Sheets of the epoxy resin composite matrix, reinforced with the carbon fibers generally have excellent tensile properties, low densities, high thermal and chemical stabilities in the absence of oxidizing agents, good thermal and electrical conductivities, and is a recyclable ecologically friendly material. Were fabricated carbon fiber/epoxy composite cylindrical plates with discretely changed curvature of a surface. We used carbon fibers 1K plain ultralight weave. For the plates’ forming we used high temperature epoxy resin. Curved carbon composite sheets were formed on the surface of a mold with the cylindrical surface.  The plates is cured in two stages: with longitudinal and than with  cross orientation. At the assembling in a package the curved composite plates with the longitudinal and cross steady states, is formed the bi-stable hinge, characterized with double-well potential, revealed in their "Snap-through" behavior when transformed from folded to deployed configuration. Such packages can find application in a space based unfolding designs. Experimentally were prove possibility of application of such kinematic pair, in which there is no rubbing surfaces, during the kinematic pairs’ parts relative movement, and accordingly, the friction among the rings of the kinematic pair absents at all.


Introduction 

The field of application of Carbon composites involves huge part of nowadays space, military and civil technologies. At the same time, production of composite materials increases and price of composites reduces. Thus, this field is expending daily with huge steps. But high rigidity, good electro and thermal transmission, low density, low thermal expansion, chemical stability and eco-friendly nature also makes it more popular and useful material.  Our main goal was to create metal-carbon bi-layer composites, examine their bi-stable behavior and study its properties and nature, and their possible use in original space based devices. Finally, the use of composite materials will be investigated, with the aim of improving the mechanical properties of these structures.

 Actuality of the Project

Deployable framework for space constructions such as antennas or satellites (on which we are currently working on), contains linking kinematic pairs of single units, such as pivots. Pivot limits any possible movement, but not the rotation around its axe (with low friction). During the long-distance space journey (for instance, during voyage between Earth and Mars, which takes up to 9 month), deployable frameworks will lost their character and become rigid because of diffusion between contacting  surfaces of the cinematic pairs.1 Almost in a month, rotation of pivot’s axis into rotary frame, and unfolding of the construction will become impossible. We’ve are working with different bi-layer composites such as bi-metal (brass and stainless steel), fiberglass-brass and carbon-metal composites and suppose that the carbon-brass bi-layer composite materials are one form the optimal way for solution of this problem. We are constructing elastic cylindrical membranes, which will replace pivot linking systems between kinematic pairs. We’ve combined such cylindrical membranes with different curvature radius and made two different types of links:

1. When axis of curvature is oriented along the rotating axis of kinematic pair 

2. When axis are oriented toward the rotating axis of kinematic pair.

The Objects and the Goals of the Research. 

 The object of the research are bi-layer composites. We examined  carbon-bras composites sintesized in the laboratory conditions in designed by us applications - “Solar engine” working  model. This model has carbon-brass bi-layer strips as "working body" of the heat engine. 2One of the layers is made of prestrained carbon fibers or from fabrics with different orientation of carbon fibers and different density. Also is used fabrics with different types of weaving (plane, satine, twell), which was glued, or polymerized on a metal membrane, and reinforced with an epoxy matrix. The thermal and mechanical properties of the composites, as well as the exact combination of parameters was measured experimentally: The research was done using carbon fibers and different types of epoxy resin monomers, purchased by the grant from  the Rustaveli Fundation and the award from the SpaceX corporation, given to one of the members of this project. However, despite the undoubtedly positive outcomes of the mentioned research, the little amount of the acquired information, doesn’t provide foundation to statistically reliably predict the optimal results, which makes the continuation of the research under the3 condition of the acquired founding the work of a current interest. 

Theoretical and Experimental Comparisons.    

 We’ve compared different bi-layer composite materials with different coefficients of thermal expansion: Carbon - 2-6 (10-6 m/(m K); Brass - 18.7 (10-6 m/(m K); Stainless Seel - 11-12 (10-6 m/(m K);

Calculating and measuring difference between Bimetallic and Carbon-Brass composite strips with formula: 4

Where E1  and h1  are the Young's Modulus and height of Material One and E2   and h2  are the Young's Modulus and height of Material Two. 7  is the misfit strain, calculated by:  10

Where α1 is the Coefficient of Thermal Expansion of Material One and α2 is the Coefficient of Thermal Expansion of Material Two. ΔT is the current temperature minus the reference temperature (the temperature, where the beam has no flexure). We found that following composites has the fillowing characteristics: 

Carbon-Brass Composite: 10,3 * 106 m-1;    Bi-metallic Strip: 4,25 * 106 m-1.

Were made and investigated bimetallic and a composite following membrans: 1. Stainless Steel - Bras (bimetalic); 2. Fiber Glass - Brass; 3. Carbon Plain Twell -Brass; 4 Unidirectional Carbon - Brass. Picture of the experimental stand  and results are shown in the below table:

 7

For fabricating the membranes with property of bistability characterized with the "Snap-through" behavior, we carried out a series of experiments, changing carbon fabrics, epoxy resin  impregnations and the curing modes. The best result obtained using carbon 1K Plain ultra light twell prepreg impregnated with low temperature carbon epoxy resin with curin temperature 1200c at the first stage (Curing during 60min), and then increasing curing temperature, up to 1350c, and holding during 75 min. During preliminary curing the membrane was fixed in the cylindrical mold with 450 orientation of fibers relative the cylinder axis. In the finish stage of the curing partially cured membrane was turned on 900 and fixed in this position under bondage. Mechanical parameters of the bi-stable membranes experimentally were investigated. 13

The table displays data of experiment where is shown dependence of force on a membrane bending angle ϕ

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   Angle   ϕ (grad) F1(N) F2(N) F3(N) <F>  ΔF ΔF/F   (%)


-15 0.132 0.11 0.1 0.114 0.012 10.5
0 0.052 0.05 0.05 0.056 0.006 11.3
15 0.03 0.05 0.06 0.047 0.011 23
30 -0.038 -0.034 -0,03 -0.034 0.0027 7.8
45 -0.095 -0.09 -0.082 -0.089 0.0047 5.2
60 -0.11 -0.10 -0.09 -0.101 0.0067 6.7
75 -0.14 -0.14 -0.13 -0.137 0.022 16.3
90 -0.18 -0.16 -0.16 -0.167 0.009 5.3
105 -0.22 -0.19 -0.20 -0.203 0.0043 2.1
120 -0.25 -0.24 -0.28 -0.257 0.0016 6.2
135 -0.26 -0.25 -0.27 -0.26 0.007 2.6
150 -0.25 -0.25 -0.27 -0.257 0.009 3.5
165 -0.27 -0.26 -0.27 -0.267 0.0013 1.6
180 0.05 0.02 -0.01 0.02 0.013 6.6
195 0.45 0.42 0.42 0.43 0.013 3.1
210 4.8 4.8 4.8 4.8

out of range

The experimental data displayed in the table and the diagram constructed according to these data are specified about existence of a double-well potential, revealed in their "Snap-through" behavior when transformed from folded to deployed configuration. 


Analyze

After theoretical analyzes we were expecting that our invented Carbon- Brass composite would have been almost 2,5 times more sensible for thermal gradient then traditional Bi-metallic composite. As experiments proved (shown on the table under Pic.5) Carbon bilayer composite comes out 9 times more efficient using 18% less temperature in

3,6 less time. Benefits of our Carbon-Brass Composite materials are clear and perfectly visible, and so is the high pricing of Carbon Fiber. But as technologies improves Carbon materials are getting cheaper daily, thus it’s logical and easily predictable that all bi-metallic strips will be replaced with Carbon bi-layer composites in near future.

Conclusions 41

After proving efficient of Carbon bi-layer composites both theoretically and experimentally, we examined it in some applications: - “Solar engine” working  model with the bi-layer strips as working body; - We created rigid transformable framework with carbon composite membranes instead of kinematic pairs and investigated  property of Carbon fiber curved membranes – characterized  with double-well potential. Such membrane packages can find application as a  kinematic pairs of the fifth order in a space based unfolding designs. Experimentally were prove possibility of application of such kinematic pair, in which there is no rubbing surfaces, during the kinematic pairs’ parts relative movement, and accordingly, the friction among the rings of the kinematic pair absents at all.

References

1. R. M. Jones, Mechanics of Composite Materials, Taylor and Francis Group, New York, NY, USA, 2nd edition, 1999.
2. M. R. Wisnom, M. Gigliotti, N. Ersoy, M. Campbell, and K. D. Potter, “Mechanisms generating residual stresses and distortion during manufacture of polymer-matrix composite structures,” Composites A, vol. 37, no. 4, pp. 522–529, 2006. View at Publisher • View at Google Scholar • View at Scopus

3. M. L. Dano and M. W. Hyer, “Snap-through of unsymmetric fiber-reinforced composite laminates,” International Journal of Solids and Structures, vol. 39, no. 1, pp. 175–198, 2001. View at Publisher • View at Google Scholar • View at Scopus

4. M. R. Schultz, M. W. Hyer, R. Brett Williams, W. Keats Wilkie, and D. J. Inman, “Snap-through of unsymmetric laminates using piezocomposite actuators,” Composites Science and Technology, vol. 66, no. 14, pp. 2442–2448, 2006. View at Publisher • View at Google Scholar • View at Scopus

5. D. J. Leo, Engineering Analysis of Smart Material Systems, John Wiley & Sons, Hoboken, NJ, USA, 2007.



 

ბოლო ცვლილება: ოთხშაბათი, ივლისი 8 2015, 08:35