Experimental approaches on a fibre-reinforced composite laminate for pressure tanks applications.

Teodorescu-Draghicescu, Horatiu ; Stanciu, Anca ; Vlase, Sorin 等

1. INTRODUCTION

Fibre-reinforced composite laminates are widely used for various applications. However, the wall structure for a pressure tank requires some plies sequence to optimize the resin and reinforcement consumption and to obtain equal stiffness.

Stiffness evaluation of composite laminates is for a great importance in designing composite structures especially suited for aerospace, defence and automotive industries, but also for transportation, chemistry and food industries.

2. CRITICAL OVERVIEW

It is well known that composite laminates with aligned reinforcement are very stiff along the fibres, but also very weak transverse to the fibres direction. This fact is more obvious in the case of advanced composite laminates reinforced with anisotropic carbon or aramid fibres. Getting equal stiffness of laminates is a demand (Scutaru et al., 2009).

The solution to obtain equal stiffness of laminates subjected in all directions within a plane is presented by various authors by stacking and bonding together plies with different fibres orientations (Hull & Clyne, 1996; Clyne & Withers, 1993; Knops, 2008). A composite laminate subjected to off-axis loading system presents tensile-shear interactions in its plies. Tensile-shear interactions lead to distortions and local micro-structural damage and failure, so in order to obtain equal stiffness in all off-axis loading systems, a composite laminate have to present balanced angle plies (Chou, 1992; Harris, 1998; Ashby, 2005; Vlase et al., 2008).

3. THE COMPOSITE LAMINATE

The fibre-reinforced composite structure suited to manufacture a 10 [m.sup.3] pressure tank presents the following plies sequence:

* 1 layer of 450 g/[m.sup.2] chopped glass mat;

* 1 layer of 450 g/[m.sup.2] chopped glass mat;

* 1 layer of 800 g/[m.sup.2] glass fabric impregnated with polyester resin;

* 1 layer of 800 g/[m.sup.2] glass fabric impregnated with polyester resin;

* 1 layer of 800 g/[m.sup.2] glass fabric impregnated with polyester resin;

* 1 layer of 800 g/[m.sup.2] glass fabric impregnated with polyester resin;

* 1 layer of 600 g/[m.sup.2] chopped glass mat impregnated with polyester resin;

* 1 layer of 600 g/[m.sup.2] chopped glass mat impregnated with polyester resin.

The pressure tank has been manufactured using the hand lay-up process. This manufacturing process has been chosen to optimize the resin and reinforcement consumption and for its simplicity.

4. RESULTS

From the wall structure of the fibre-reinforced composite laminate, various specimens have been cut and subjected to tensile and three-point bend tests on Lloyd's Instruments testing machines using Nexygen Plus testing software.

For tensile tests, some testing features are:

* Test speed: 1 mm/min;

* Specimens mean thickness: 7.24 mm;

* Specimens mean width: 9.39 mm;

* Gauge length: 50 mm.

For three-point bend tests, testing features are as following:

* Test speed: 3 mm/min;

* Span: 110 mm;

* Specimens mean thickness: 7.36 mm;

* Specimens mean width: 14.96 mm;

The distributions of Young moduli, stiffness and flexural rigidities are presented in figs. 1-5.

[FIGURE 1 OMITTED]

[FIGURE 2 OMITTED]

[FIGURE 3 OMITTED]

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[FIGURE 5 OMITTED]

5. CONCLUSIONS AND FUTURE RESEARCH

Tensile tests accomplished on fibre-reinforced composite laminate with the presented plies sequence, show medium values of stiffness and Young moduli. Three-point bend tests present interesting values. Despite values scattering of Young modulus of bending, the values of flexural rigidity show a quite good composite laminate due to the choice of the plies sequence. Future researches will be accomplished in the following domains: tensile and three-point bend tests using the same plies sequence but with a nonwoven polyester core and a finite element analysis on this structure and other composite architectures with various plies sequences.

6. REFERENCES

Ashby, M.F. (2005). Materials Selection in Mechanical Design, Butterworth-Heinemann, 3rd edition, ISBN: 978-0750661683

Chou, T.W. (1992). Microstructural Design of Fibre Composites, Cambridge University Press, ISBN: 978-0521354820

Clyne, T.W. & Withers, P.J. (1993). An Introduction to Metal Matrix Composites Materials, Cambridge University Press, ISBN: 978-0521418089

Harris, B. (1998). Engineering Composite Materials, Maney Materials Science, 2nd edition, ISBN: 978-1861250322.

Hull, D. & Clyne, T.W. (1996). An Introduction to Composite Materials, Cambridge University Press, 2nd edition, ISBN: 978-0521381901

Knops, M. (2008). Analysis of Failure in Fibre Polymer Laminates: The Theory of Alfred Puck, Springer, ISBN: 978-3540757641

Scutaru, M.L.; Katouzian, M.; Vlase, S.; Teodorescu-Draghicescu, H. & Chiru, A. (2009). An Estimation of the Viscoelastic Parameters of laminated Composites, Proceedings of the 4th IASME/WSEAS International Conference on Continuum Mechanics, pp. 140-145, ISBN: 978-960-474-056-7, Cambridge, February 2009, WSEAS

Vlase, S.; Scutaru, L.M. & Teodorescu-Draghicescu, H. (2008). Some considerations concerning the use of the law of mixture in the identification of the mechanical properties of the composites, Proceedings of the 6th International Conference of DAAAM Baltic Industrial Engineering, R. Kyttner (Ed.), pp. 577-582, ISBN 978-9-985-59783-5, Tallinn, Estonia, April 2008, DAAAM International, Vienna