Tensile testing specimen geometry

Tensile test specimens have been fabricated based on ASTM D 3039 for off-axis angles. The materials chosen for fiber and matrix were E-Glass UD-weaves and ML-506 Epoxy resin, respectively. UD-weave fiber lay-up and test specimen geometry are shown in Figure 1 and Figure 2 ... 

Fig. 11. Gleeble3500 used for the temperature-depending tensile test and geometry of the specimen.

Fig. 1. Schematic of common specimen geometries used in fatigue testing of polymeric materials, (a) Tensile test specimen, (b) Flexural test specimen.

Apart from the short beam shear test, which measures the interlaminar shear properties, many different specimen geometry and loading configurations are available in the literature for the translaminar or in-plane strength measurements. These include the losipescu shear test, the 45°]5 tensile test, the [10°] off-axis tensile test, the rail-shear tests, the cross-beam sandwich test and the thin-walled tube torsion test. Since the state of shear stress in the test areas of the specimens is seldom pure or uniform in most of these techniques, the results obtained are likely to be inconsistent. In addition to the above shear tests, the transverse tension test is another simple popular method to assess the bond quality of bulk composites. Some of these methods are more widely used than others due to their simplicity in specimen preparation and data reduction methodology. 

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. 

The EWF tests were named with a eode indicating material, erosshead rate and orientation, in that order. In this way, PC20-10T (or P) results correspond to tests carried out on PC20 blends tested at 10 mm/min in 90° (or 0°) crack propagation with respect to the melt flow direction. It is important to mention that even the fact that tensile parameters were determined on thicker (4 mm) dumbbell specimens could invalidate their use in EWF validations due to some morphological and crystallinity differences, some SEM observations and DSC measurements on plaques and dumbbell test specimens verified that these microstructural features are quite similar on both specimen geometries (Table 1). 

The isothermal tensile fatigue tests were performed at 566°C (1050°F) in air. The specimen geometry was the same edge loaded tensile geometry used in the creep tests. The test cycle involved linearly increasing the tensile stress from the minimum value (14 MPa) to the maximum value over a one second period. The sample was held at the maximum stress for one second and then the stress was linearly reduced to the minimum value over an additional one second period. 

TDCB (tapered double-cantilever beam) specimens were used to determine the healing efficiency and repeatability of the healing. The specific geometry of the TDCB can be seen in Figure 7.27(a). The healing efficiency was evaluated by a tensile test using the Q-TEST 150... 

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