Experimental results concerning the geometric, structural and dimensional differences in fiber reinforced composites.

Vlase, Sorin ; Modrea, Arina ; Burca, Ioan 等

1. INTRODUCTION

This part presents experimental results concerning composite materials reinforced with fibers. In the first part we have presented the influence of dimensional, structural or geometric differences on the values of the engineering constants of a composite. The theoretical considerations (Modrea, 2001, a,b,c,d) were proved by experimental procedures.

2. TESTA AND SPECIMENS

To verify the mentioned properties was tested specimens made respecting the existing standards. The tests was made for traction and bending.

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In fig.1 and 2 are presented some plastic specimens with the industrial name of PEJS (low density poly ethylene) and PEID (high density poly ethylene) used in the tests. These materials were made by Intreprinderea Mecanica Targu-Mures. The specimens were organized after the type of the test, in many groups, every group having ten specimens and some reserved specimens. In the case when the specimens were destroying near the ends, they were changed by a reserve specimen.

In the same time were executed specimens for the bending test, respecting the existing standards.

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Other specimens for traction and bending tests for a composite material reinforced with carbon fibers. These were made to S.C.COMPOSITE srl Brasov, for traction (fig.3) and bending (fig.4) tests.

To the same enterprise was made specimens with resins matrix and glass fibers, oriented parallel, perpendicular and to an angle of 45[degrees] (fig.5).

3. EXPERIMENTAL RESULTS

For the traction tests was used the machine existing in the laboratory of TRANSILVANIA University. Tests for the materials PEID and PEJD with the series numbered T01 and T02 was made. In one series the specimen was numbered between one and ten.

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For the four series of tests was obtained the following values for the Young modulus: [E.sub.T01]=271,145MPa; [E.sub.T02]=203,951 MPa ; [E.sub.T03] = 229,396 MPa ; [E.sub.T04] = 196,108 MPa. The specimens made by resin reinforced with glass fibers, FSU and FSB, parallel with the specimen, were tested to traction. The dependence force--displacements was represented in fig.7. The series of these specimens was numbered T05 and T06.

The specimens numbered FSMB-1 to FSMB-10 were tested to bending and the dependence force displacement is presented in fig. 9.

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4. CONCLUSIONS

The calculus made for the analyzed specimens compared with the experimental results shown that for a number of specimens the measured results are outside the calculated bounds of elastic moduli. This conclusions denote that the difference between the theoretic dimension, geometry and structure and the real composite conduce to difference, sometimes notable, between the calculated and real values of the mechanical properties. From these considerations results that is necessary to study how the differences mentioned can influence the properties of the composite material.

5. REFERENCES

Goia, I., Modrea, A., s.a. (1999). Calculus of the Mechanical Properties for the Composite Materials. A IX-a Conferinta internafionala CONAT, Brasov

Modrea, A., s.a. (2001, a). Evaluation of the elastic parameter for a composite when the strain/stress field is obtain via finite element method. A III-a Conferinta de dinamica masinilor, Brasov, pp.365-370

Modrea, A., s.a. (2001, b). Evaluation of homogenized coefficients for fiber reinforced plastic. A III-a Conferinta de dinamica masinilor, Brasov, pp.371-374

Modrea, A., s.a. (2001, c). Mathematical Background for Evaluation of Homogenized Coefficients for Fiber Reinforced Plastic (FRP). A III-a Conferinta de dinamica masinilor, Brasov, pp. 375-378

Modrea, A., s.a. (2001, d). Mathematical Background for Evaluation of Homogenized Coefficients for Fiber Reinforced Plastic (FRP). A III-a Conferinta de dinamica masinilor, pp. 375-378, Brasov