Biaxial Tensile Test

A biaxial tension device (Figme 5.4) has also been used to characterize the tensile behavior of the reinforcements. 

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Lecompte D, Smits A, Sol H, Vantomme J, Van Hemelrijck D. Mixed numerical-experimental technique for orthotropic parameter identification using biaxial tensile tests on cruciform specimens. Int J Sobds Struct 2007 44 1643-56. 

However, the value of the maximum strain recorded at the end of the forming process on the tightest tow needs to be compared to the limit of the fabric determined by performing biaxial tensile test on the same fabric. Figure 5.11 shows the result of the... 

The value of F,2 then depends on the various engineering strengths plus the biaxial tensile failure stress, a. Tsai and Wu also discuss the use of off-axis uniaxial tests to determine the interaction strengths such as F.,2 [2-26]. 

The [10°] off axis tension specimen shown in Fig 3.23 is another simple specimen similar in geometry to that of the [ 45 ]s tensile test. This test uses a unidirectional laminate with fibers oriented at 10° to the loading direction and the biaxial stress state (i.e. longitudinal, transverse and in-plane shear stresses on the 10° plane) occurs when it is subjected to a uniaxial tension. When this specimen fails under tension, the in-plane shear stress, which is almost uniform through the thickness, is near its critical value and gives the shear strength of the unidirectional fiber composites based on a procedure (Chamis and Sinclair, 1977) similar to the [ 45°]s tensile test. 

Figure 13.12 Fiber strength test articles, (a) the impregnated fiber strand specimen, unidirectional lamina tensile specimen, and NOL ring (b) 4-in. biaxial tube test specimen...

Another apparatus for general biaxial extension testing, illustrated in Fig. 8, was built at our laboratory27). A square sheet of rubber, 11.5 cm long and 1 mm thick, is clamped at the edges by several pieces of movable chucks and stretched biaxially by means of the two bars that can be displaced separately bade and forth by a servo-meachnism. Tensile forces acting on the sheet in the stretching directions are transmitted to the bars and measured by two transducers mounted at the ends of each bar. After many modifications and improvements on the mechanical and electric parts,... 

The complex strain paths undergone by industrial parts during multi-pass forming can be simulated in laboratory tests by applying to the same specimen successively two different load paths, for example, a tensile test followed by deep drawing or biaxial expansion followed by a local tensile test. The analysis of the specimens provides results similar to those for real industrial components ... 

As long as the initial deformation implies 2 < 0 (compression test, simple tensile test) followed by biaxial expansion, the limit curve... 

When a geotextile subjected to concentrated forces normal to the plane is kept under pre-tensioned conditions, the distribution and magnitude of these forces result in the puncture failure. In general, a biaxial tensile failure simulates puncture failure more appropriately than uniaxial tensile tests. The puncture properties of geotextiles are significantly affected by the fabric and soil parameters. ... 

The challenges inherent in the measurement of stress-strain response of thin film materials by means of direct tensile testing are commonly more than offset by the distinct advantage that properties characterizing deformation resistance of the material in the plastic range can be determined under isothermal conditions for a relatively simple state of stress on the specimen. However, these techniques are not readily amenable to modifications that can accommodate uniaxial compression, simple shear stress, equi-biaxial stress or states stress on the specimen. As a result, it is difficult to draw conclusions concerning the dependence of plastic response on stress path history. It is noted that results for some cyclic tension-compression experiments were reported by Hommel et al. (1999). 

The procedure described above is straightforward in principle. However, in practice, great care must be taken in the test fixture design to assnre that applied loads cause a uniform state of stress in the test specimen. Two types of tests that have been developed for this purpose include (1) the simple tensile test for uniaxial states of stress, (2) the thin-walled tube subjected to combined torsion and internal pressure, for biaxial states of stress. Some theoretical aspects of the simple tensile test are developed in the sample problem which follows. For a more detailed discussion on experimental procedures for characterizing the material properties of composite materials, see Caisson and Pipes and Whitney et al. ... 

Tyvek 34g/m samples were prepared by cutting rectangular pieces of dimensions of 0.1524 m x 0.1524 m which were compression molded in varying layer placed biaxially and in a parallel manner and held together by tie layers of thin clear PE film. The laminates were molded at a temperature of 421.48°K, at a 2.2679 kg load for 720 s using a 45359.237 kg compression press machine. Tensile test strip specimens were prepared from the laminates cut at various angles of orientation 0,15,30,45,... 

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