Flexural short-beam shear

Fig. 5.5. Normalized irKerfacial shear strength of unsized (bare) and sized E-glass fiber-epoxy matrix eomposites measured from the interfaeial testing system (ITS, equivalent to fiber push-out test), short beam shear (SBS) test, 0° flexural test and 90° flexural test. After Drown et al. (1991).

Figure 7. Normalized values for the interfacia] shear strength as measured by the ITS plotted against the short beam shear strength (SBS), 0° flexure strength, and 90° flexure strength for the bare and Epoxy-sized fibers.

Figure 3. Flexural strength, flexural modulus, and short beam shear at 550°F of non-post cured P13N/boron specimens after aging at 550° F...

Flexural Properties of Plastics and Electrical Insulating Materials Bearing Strength Short Beam Shear... 

The apparent inierlantinar shear lest uses a short beam flexure loading mode to measure the shear strength along the plane of lamination. The analysis of the test is... 

Figure 4 Interlaminar shear test by short beam flexure failure modes.

In the broad sense, interlaminar adhesion means the adhesion between any laminations of similar or dissimilar materials and hence could be taken to include just about any adhesion test. One particular type for fiber-reinforced plastics, which is known as interlaminar shear strength, is normally considered as a short beam flexural test (sec Chapters 9 and 18). A method peculiar to laminated plastics tube is given in BS 2782, Method 346A [59] and called cohesion between layers of laminated tube. A sample of tube is subjected to compression to induce shear forces between layers and delamination observed by eye,... 

The deflection of a beam as computed by the ordinary formulas is that due to flexural stresses only. The deflection in honeycomb (Chapter 7 Sandwiches) and short beams due to vertical shear can be high, and should always be checked. Because of the nonuniform distribution of the shear over the cross section of the beam, computing the deflection due to shear by exact methods is difficult. It may be approximated by ... 

This measurement is performed by a three-point flexure method on short beams, with the span-to-width ratio chosen to produce interlaminar shear failure [1,2]. The geometry of this test is described in Figure 1. Fibres are oriented in the direction perpendicular to the axes of the supports. 

Under three point bend loading of a composite (beam), cracks may be developed due to tensile stresses at the lower stratus of the specimen as well as compression stresses at the upper one, or due to interlaminar shear. The type of failure depends on the ratio of span to depth (L/D). Short beam specimens usually fail in shear and long ones by tensile or compression stresses. For interlaminar shear strength (ILSS) tests, a L/D = 5 was chosen (ASTM-D-2344-76). In case of flexural strength tests, this ratio was fixed to 40 (DIN 29971). 

Tension Compression Shear Flexure Bearing short beam ... 

When the displacement components of a member are small, a wide range of linear analysis tools, such as modal analysis, can be used, and some analytical results are possible. As these components become larger, the induced geometrical nonlinearities result in effects that are not observed in linear systems. When finite displacements are considered, the flexural-torsional dynamic analysis of beams becomes much more complicated, leading to the formulation of coupled and nonlinear flexural, torsional, and axial equations of motion. The analysis of these systems becomes even more complicated when shear deformation effect in flexure and secondary torsional moment deformation effect (STMDE) in torsion, which are significant in many cases (e.g., short beams, beams of box-shaped cross sections, folded structural members, beams made of materials weak in shear, etc.), are taken into account. 

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. 

Finally, one can think of beginning to move the brace in each bay horizontally, such that a hybrid structure between a pure moment frame and a braced frame is achieved. This is known as an eccentrically braced frame (Fig. 13b). In these structures, the central portion of the beam, known as the link, will deform and yield in shear if the link is short and in a combination of flexure and shear if the link is longer. Eccentrically braced frames have performed extremely well in recent earthquakes (Fig. 20), with numerous such structures providing superior performance during the 2011 Christchurch earthquake (Clifton et al. 2011). 

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