Tensile shear strength measurement

In the 90° direction, the fiber-matrix interphase is a controlling factor in the flexural strength. Here a 35% increase in flexural strength is measured in direct proportion to the increase in interfacial shear strength measured with the ITS tests. The transverse tensile strength of the fiber-matrix interphase is greater for the finished fiber than for the bare fiber. Apparently the lower toughness of the... 

Tensile shear strength, psi, measured at 25°C on aluminum when cured 7 days at 25 °C 2050 1050... 

A standard test report usually documents the resulting measurements, such as tensile shear strength and peel strength. It should also indicate all the pertinent conditions that are required to ensure reproducibility in subsequent testing. It is often very useful to describe the failure mode of the tested specimens. An analysis of the type (or mode) of failure is an extremely valuable tool to determine the cause of adhesive failure. The failed joint should be visually examined to determine where and to what extent failure occurred. The percent of the failure that is in the adhesion mode and that in the cohesion mode should be provided. A description of the failure mode itself (location, percent coverage, uniformity, etc.) is often quite useful. The purpose of this exercise is to establish the weak link in the joint to better understand the mechanism of failure. 

Tensile Shear Tests. The lap shear or tensile shear test measures the strength of the adhesive in shear. It is the most common adhesive test because the specimens are inexpensive,... 

The shear strength measurement was conducted with an Instron tensile test machine of the constant-rate-of-crosshead movement type. A shear tool described in ASTM D732 was used. The samples were run at a crosshead speed of 0.05 In/mln. 

Tensile-shear strength n. A measure of the shear strength of an adhesive bond in which two members are bonded in a lap joint, then pulled at both ends until the joint fails in... 

Tensile-Shear Strength n A measure of the shear strength of an adhesive bond in which two members are bonded in a Lap Joint, then pulled at both ends until the joint fails in shear. The strength is reported as the tensile force divided by the shear area (Pa). A double lap joint may be specified. Many tests of tensile-shear strength are listed among the ASTM Standards (www. astm.org). 

In the automotive industry, some car manufacturers are using the wet patch or wet cataplasma they place samples of bonded parts in contact with cotton impregnated of water, put it into a plastic impervious bag and then store it at a given temperature for a given period of time. They measure mechanical resistance (such as tensile shear strength) before and after this test, and they have their own rules of experience in order to decide the percentage loss of properties, which is acceptable for a given application. 

Shear cell measurements offer several pieces of information that permit a better understanding of the material flow characteristics. Two parameters, the shear index, n, and the tensile strength, S, determined by fitting simplified shear cell data to Eq. (6), are reported in Table 2. Because of the experimental method, only a poor estimate of the tensile strength is obtained in many cases. The shear index estimate, however, is quite reliable based on the standard error of the estimate shown in parenthesis in Table 2. The shear index is a simple measure of the flowability of a material and is used here for comparison purposes because it is reasonably reliable [50] and easy to determine. The effective angle of internal... 

In addition to the direct measurements of fiber-matrix interface properties discussed in Section 3.2, a number of testing techniques have been devised to assess the fiber-matrix interface bond quality by inference from the gross mechanical properties such as interlaminar shear strength (ILSS), translaminar or in-plane shear strength, and transverse tensile strength. These testing techniques invariably employ... 

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. 

As with tensile properties, both compressive strength and modulus depend on the fiber content and hber orientation (see Table 5.8). The interlaminar shear strength reported in Table 5.8 is a measure of the shear strength in the thickness direction of the SMC sheet. It is determined by three-point flexural testing of beams with short span-to-depth ratios and is considered to be a quality-control test for molded composites. 

Two different polyacrylonitrile precursor carbon fibers, an A fiber of low tensile modulus and an HM fiber of intermediate tensile modulus were characterized both as to their surface chemical and morphological composition as well as to their behavior in an epoxy matrix under interfacial shear loading conditions. The fiber surfaces were in two conditions. Untreated fibers were used as they were obtained from the reactors and surface treated fibers had a surface oxidative treatment applied to them. Quantitative differences in surface chemistry as well as interfacial shear strength were measur-ed. 

Here we have conducted experiments to develop an understanding of how the commercial size interacts with the matrix in the glass fiber-matrix interphase. Careful characterization of the mechanical response of the fiber-matrix interphase (interfacial shear strength and failure mode) with measurements of the relevant materials properties (tensile modulus, tensile strength, Poisson s ratio, and toughness) of size/matrix compositions typical of expected interphases has been used to develop a materials perspective of the fiber-sizing-matrix interphase which can be used to explain composite mechanical behavior and which can aid in the formulation of new sizing systems. 

The increase in ILSS for the epoxy-sized fibers over the bare fibers is 12.4%, approximately 50% of the increase observed in the interfacial shear strength as measured by ITS testing. Changes in the failure mode at the fiber-matrix interface may account for the differences. The sized fibers produced large matrix cracks that grew quickly to catastrophic size under load. This would tend to limit the increase in composite shear properties if at every fiber break in the tensile surface of the coupon a matrix crack was created. The presence of these matrix cracks... 

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