Some aspects of technologies for obtaining the samples from composite material with layers and particles reinforcement.

Nedelcu, Dumitru ; Carcea, Ioan ; Ghenghea, Laurentiu 等

1. INTRODUCTION

The main problem of this paper is to establish the technology steps for obtaining the sample of composite material with layers reinforcement and particles Si-C reinforcement.

At worldwide level there are a certain number of universities and research institutes that have a "tradition" in the activity specific to this domain. We have to mention here that the materials required for these research studies are at accessible prices and have got suitable physical and mechanical properties (Hamann, R., Fougeres, R., 1991).

The engineers can design composites quite rigid and strength, in order to answer the most strictly specified demands, providing the number of layers, kind and thickness (matrix and reinforcement), the packing sequence and the fibers orientation. Until now we develop some research concerning the characteristics of composite material using the pressure technology (references, Cobzaru. P., 2004 & Gramescu, T., 2002).

Now we want to use the liquid forging technology for obtaining the composite materials with layers reinforcement (fig.2, references Ciocardia C., 1991 & Cazimirovici, E., 1990) and to establish the technology steps for obtaining the samples of composite materials with particles reinforcement (figure 1). The new idea consists in determining the optimum quantity of aluminum form matrix at the interface level, without diminishing the reinforcing capacity of the composite materials. For further research we plan the following two main research parts:

a). Experimental research regarding the:

--tensile strength of the MMC for various technological parameters of liquid forging;

--fractographical research studies regarding the tensile strength of the MMC for various technological parameters of liquid forging;

--metallographic research studies of optical and electronic microscopy regarding the damaging of the composite materials; b). Experimental research concerning the:

--development of mathematical model for damaged composite analysis under the dynamic loading conditions;

--the analysis of damaged layered composite during the dynamic conditions loading;

--the dynamic study of damaged composite materials with particles reinforcement;

--the analysis of interior and interface cracks;

--the analysis of different damages upon the internal tensions;

--the analysis of damaged upon the characteristics of composite materials using destructive methods (optical microscopy) and nondestructive methods (ultrasonic testing, eddy current testing).

2. TECHNOLOGY USE

The methodology and techniques that will be used for obtaining the composite materials with layers reinforcement consist in running the following principal phases (figure 1):

--the premould consists of a rectangular metallic support on which we shall align the uniformly tensioned waves;

--the premould will be introduced in the steel mould made T20MSNC260 and the whole assembly will be heated in an inert atmosphere of Argon at temperatures of 25[degrees]C, 600[degrees]C, 900[degrees]C;

--the inner surfaces, obtained by splintering, that make contact with the liquid matrix, will be protected with a layer of refractory paint based on aluminum oxide applied at 150[degrees]C;

--the contact surfaces between the mould-piston and the mould-bottom lid will be covered with a refractory paint based on graphite in industrial alcohol in order to provide a perfect impermeability;

--aside, in an oven, there will be prepared the liquid metallic matrix with the following chemical compositions: a-Al100%, b-Al75Zn25;

--casting temperatures 700[degrees]C, 750[degrees]C, 800[degrees]C, 850[degrees]C, 900[degrees]C will be selected such as the fluidity determined with the Kerry spiral should be maximal;

--after removing the slag, the liquid matrix is poured over the premould from the mould and the piston goes down until it is reached a pressure of 25MPa;

--at the end of solidification, the newly formed composite will be removed;

--according to the standards in force there are taken several test bars and there are selected longitudinal and transversal surfaces to be analyzed;

--the test bars will be grouped in batches for microscopic metallographic research studies, inclusively for the electron-scan microscope and for their breaking by traction;

--after the electrolytic polishing and finishing, the surfaces prepared for analysis are chemically attacked with Lacombe and Finkeldey reactive;

--half of the batch of the test bars broken by traction will be boiled in caustic soda in order to destroy the metallic matrix infiltrated among the fibers. Afterwards, the layer of aluminum carbide will be removed from the fiber surface by cleaning in ultrasound field;

--in the next phase we shall make accurately measurements on the electron-scan microscope in order to quantify the effort bearing diameter of the carbon fibers and the length of the reinforcement extractions from the matrix;

--by crystallographic calculations it is got the thickness of the aluminum carbide layer.

[FIGURE 1 OMITTED]

This is a feed-back working procedure that ensures the possibility of an objective measurement of the outputs--an essential condition for getting high-quality results.

The methodology and techniques that will be used for obtaining the composite materials with particles reinforcement consist in running the following principal phases (figure 2):

--introduction the Si-C particles into the aluminum liquid matrix;

--mixed all the mixture using one palette with driving belt;

--heating the all mixture;

--cooling of all mixture into the crystallization;

--solidification;

-the extraction of composite material reinforcement.

The future research consists of obtaining the samples and making the following:

--determination of the tensile strength curve for certain well-determined technological conditions and reinforcement volumes;

--the fractal analysis of the breaking surfaces;

--IR spectroscopy (chemical structure, links and so on).

3. CONCLUSIONS

The technical impact could be evaluated through the intern impact that the new composites will have over the substantial growth of productivity and production's quality, through the possibility of using the technology and other categories of composites, with the possibility of subsequent research studies in connection with composites with organic matrix, composites with reinforcing particles and hybrid composites.

[FIGURE 2 OMITTED]

The economic impact could be evaluated through an increased productivity and a much better quality of products, having consequences over the company's profit.

4. REFERENCES

Cazimirovici, E., et al (1990). Teoria si tehnologia deformarii prin tragere, The theory of cold plastic deformation technology, Technical Publishing, pp. 160, ISBN 973-310266-0, Bucharest

Ciocardia, C. et al (1991). Tehnologia presarii la rece, The cold plastic deformation technology, EDP Bucharest, pp. 437, ISBN 973-30-2314-0, Bucharest

Cobzaru, P. (2004). Materiale compozite, Composite materials, EDP Bucharest, pp. 34, 38, ISBN 973-30-1445-1, Bucharest

Hamann, R., & Fougeres, R., (1991). Proceedings of the 12th Riso International Symposium on Materials Science, Roskilde, Denmark, pp. 373, Roskilde

Gramescu, T., (2002). Tehnologii de mecanica fina, The fine mechanics technology, Tehnica-Info Publishing, pp. 261-262, ISBN 9975-63-165-7, Chisinau

Nedelcu, D., Pruteanu, O.V., (1998). Aspecte ale formarii canelurilor exterioare prin deformare plastica la rece utilizand metoda Taguchi, Some aspects concerning the cold plastic deformation of exterior grooves using Taguchi method, Tehnica-Info Chisinau, pp. 34-38, ISBN 9975-910-96-3, Chisinau

Pruteanu, O.V., Nedelcu, D.,(1996). The stress analysis on deformation roll, Proceedings of 7th International DAAAM Symposium, Katalinik, B. (Ed.), pp. 361-362, ISBN 3-901509-02-X, Vienna, Austria, October 1996, Vienna