Tensile Test

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CHAPTER 5
TESTING AND MACHINING OF COMPOSITES
5.1 INTRODUCTION This chapter deals with the various tests conducted methods to evaluate the mechanical characteristics of the fabricated composites. Morphological analysis is also carried out using scanning electron microscope set-up to study the microstructure. It also outlines the drilling of composite specimen.
5.2 MECHANICAL TESTS
The mechanical tests were conducted for the specimens sample S1, sample S2 and sample S3 of categories C1, C2 and C3 as per ASTM standards.
5.2.1 Tensile Test
Tensile strength of a material is found out by tensile test. It is the maximum amount of tensile stress that it can withstand before failure. During the test, a uni-axial load is applied on both the ends of
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The flexural strength of a material can be tested by the tensile test. Flexural strength is defined as a material’s ability to resist deformation under load. The short beam shear tests are performed on the composite samples to evaluate the value of inter-laminar shear strength. It is a 3-point flexural test, which generally promotes failure by inter-laminar shear. The flexural strength is expressed as a modulus of rupture in MPa. The three point static flexural test is the most common flexural test. .The schematic diagram of flexural test specimen is shown is Fig. 5.4. It is performed at room temperature and close to 40% relative humidity. In this test, the specimen to be tested is subjected to a load at its midway between the supports and until it fractures and breaks. This test determines the behavior of the specimen when it is subjected to simple beam loading. Flexural test determines the maximum stress induced in the outer most fiber. The flexural test specimen at failure is shown in the figure 5.5. Sample specimens are shown in Figure…show more content…
The cutting speed, feed rate, and drill tool diameter are considered as the input parameters. A Higher cutting speed produces better surface finish and low thrust force. At high spindle speed, the heat generated at the tool edge softens the polymer matrix, which in turn produces low thrust force and good surface finish. The thrust on the tool and material removal rate are highly depends on feed rate. Low feed rate is always preferred for drilling of GFRP composites. The increase of feed rate increases the thrust force. Also the increase in feed rate increases the surface roughness. Further the decrease in feed rate reduces the material removal rate and hence reasonable feed rate is preferred for drilling of GFRP composites. The tool diameter influences the surface roughness and thrust force in drilling of GFRP composites. It seems that as the drill diameter gets smaller, the drilling space becomes smaller as well and thus the smaller cutting force is generated. Researchers found that small diameter drill produces better results in drilling of GFRP composites. But very small drill bits cannot be used for drilling of GFRP

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