Cross-beam test

Another test used to determine the shear modulus and shear strength of a composite material is the sandwich cross-beam test due to Shockey and described by Waddoups [2-17]. The composite lamina... 

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 design and manufacture is described in detail of a dashboard module from polypropylene. The lightweight monomaterial dashboard comprises an outer material of a TPO film, foam backed with an EPP foam. This decorative element, together with a highly integrated composite fibre hybrid cross beam, forms the core element of the lightweight dashboard module. The prototype consists of four individual components, and is designed in such a way that it can be built into and tested in the Mercedes A class car. 3 refs. 

The problem of definition of modulus applies to all tests. However there is a second problem which applies to those tests where the state of stress (or strain) is not uniform across the material cross-section during the test (i.e. to all beam tests and all torsion tests - except those for thin walled cylinders). In the derivation of the equations to determine moduli it is assumed that the relation between stress and strain is the same everywhere, this is no longer true for a non-linear material. In the beam test one half of the beam is in tension and one half in compression with maximum strains on the surfaces, so that there will be different relations between stress and strain depending on the distance from the neutral plane. For the torsion experiments the strain is zero at the centre of the specimen and increases toward the outside, thus there will be different torque-shear modulus relations for each thin cylindrical shell. Unless the precise variation of all the elastic constants with strain is known it will not be possible to obtain reliable values from beam tests or torsion tests (except for thin walled cylinders). 

During the tests, we also examined how the cross-correlation functions were affected when air is injected into the slurry and when cross-beam geometry is used. Table 5-1 shows the velocity when crossed-beam geometry was used. (Fig. 5-15). When compared with the normal parallel geometry, the crossed-beam geometry measures a velocity that is greater by as much as "20%. This is expected, because the cross-beam geometry correlates primarily the... 

ASTM D-1344 describes a cross-lap specimen of the type shown in Fig. 2d for determining tensile properties of adhesive bonds. Wood, glass, sandwich, and honeycomb materials have been tested as samples in this general configuration. Even under the best of circumstances, one would not anticipate the stress distribution in such a case to be very uniform. The exact stress distribution is highly dependent on the relative flexibilities of both the cross beams and the adhesive. Certainly, caution must be exercised when comparing tensile strength from this test with data obtained from other tensile tests. Probably for these reasons, this test is scheduled by ASTM for discontinuation. 

The above tests on the primary ion beam are routine. The major uncertainty in the longitudinal tandem technique is the detection efficiency of product ions. This detection efficiency can be calculated if the complementary crossed-beam experiment has been performed to yield the contour map, i.e., both the angular distribution and the velocity distribution. As has been emphasized both earlier in this chapter and in Chapter 12, this is the proper approach to the problem, but the necessary data are rarely available. The alternative is to measure the detection efficiency and, in the absence of the angular distribution data, this must be done before an accurate cross section can be obtained. In practice, it rarely is done because the measurements are not straightforward. This absence constitutes a major source of possible error in most determinations of excitation functions by the longitudinal tandem technique. 

Post-experimental data processing was performed after the test. As experimental data the load P, cross-beam displacements and digital speckle photographies were obtained. Load P (kg) was converted to stress (MPa) by the formula (Karkashadze G.G., 2004) ... 

Figure 5. Stress-cross-beam displacement curves for tested specimens.

A home-designed device was used to align the fibre with the axis of a Hounsfield tensile testing machine. The upper part of the card-board was clamped on a 5N load cell, which was fixed on the cross-beam of the tensile testing machine. The pull-out speed was 1 mm/min. Force-displacement curve was recorded on a computer. The interfacial shear strength, t, was calculated using Eq. 3. 

A unifonn monoenergetic beam of test or projectile particles A with nnmber density and velocity is incident on a single field or target particle B of velocity Vg. The direction of the relative velocity m = v -Vg is along the Z-axis of a Cartesian TTZ frame of reference. The incident current (or intensity) is then = A v, which is tire number of test particles crossing unit area nonnal to the beam in unit time. The differential cross section for scattering of the test particles into unit solid angle dO = d(cos vji) d( ) abont the direction ( )) of the final relative motion is... 

The equipment required for slow strain-rate testing is simply a device that permits a selection of deflection rates whilst being powerful enough to cope with the loads generated. Plain or precracked specimens in tension may be used but if the cross-section of these needs to be large or the loads high for any reason, cantilever bend specimens with the beam deflected at appropriate rates may be used. It is important to appreciate that the same deflection rate does not produce the same response in all systems and that the rate has to be chosen in relation to the particular system studied (see Section 8.1). 

Young s modulus is often measured by a flexural test. In one such test a beam of rectangullar cross section supported at two points separated by ia distance Lq is loaded at the midpoint by a force F, as illustrated in Figure 1.2. The resulting central deflection V is measured and the Young s modulus E is calculated as follows ... 

Epoxy acrylate (Ebecryl 3700, 50%) combined with 25% TMPTA, 25% I BOA and with DIBF-OPPI-DIDMA pigment and FC-171 as above was also used to coat panels. These panels showed no removal of coating in the cross hatch adhesion test. With 6.8j there was no loosened coating on the frontal impact surface, and only 30% was loosened on the back surface. Five hundred grams were required to scratch to bare metal with the balanced beam. Performance was... 

Experiments have also played a critical role in the development of potential energy surfaces and reaction dynamics. In the earliest days of quantum chemistry, experimentally determined thermal rate constants were available to test and improve dynamical theories. Much more detailed information can now be obtained by experimental measurement. Today experimentalists routinely use molecular beam and laser techniques to examine how reaction cross-sections depend upon collision energies, the states of the reactants and products, and scattering angles. 

Flexural strength, or cross-breaking strength, is a measure of the bending strength or stiffness of a test bar specimen used as a sample beam in accordance with ASTM D-790. The specimen is placed on supports (Figure 14.13). A load is applied to its center at a specified rate... 

After discussing the theory of positronium formation, with applications to several relatively simple systems, we shall describe various techniques used to measure positronium formation cross sections and present the results so obtained, comparing them with theoretical predictions wherever applicable. The chapter also includes a discussion of the angular dependence of the positronium formation cross section. As well as being of intrinsic interest as a test of theory, the differential formation cross section, da-ps/dQ, is also relevant for the production of energy-tunable beams of positronium atoms. This topic is treated more fully in section 7.6. 

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