Reduced bending stiffness

Cord materials such as nylon, polyester, and steel wire conventionally used in tires are twisted and therefore exhibit a nonlinear stress—strain relationship. The cord is twisted to provide reduced bending stiffness and achieve high fatigue performance for cord—mbber composite stmcture. The detrimental effect of cord twist is reduced tensile strength. Analytical studies on the deformation of twisted cords and steel wire cables are available (22,56—59). The tensile modulus E of the twisted cord having diameter D and pitchp is expressed as follows (60) ... 

In their pioneering paper on laminated plates, Reissner and Stavsky investigated an approximate approach (in addition to their exact approach) to calculate deflections and stresses for antisymmetric angie-ply laminated plates [5-27]. Much later, Ashton extended their approach to structural response of more general unsymmetrically laminated plates and called it the reduced stiffness matrix method [5-28]. The attraction of what is now called the Reduced Bending Stiffness (RBS) method is that an unsymmetrically laminated plate can be treated as an orthotropic plate using only a modified D matrix in the solution, i.e.,... 

M. S. Ewing, R. J. Hinger, and A. W. Leissa, On the Validity of the Reduced Bending Stiffness Method for Laminated Composite Plate Analysis, Composite Structures, Volume 9, 1988, pp. 301-317. 

The effect of the specific values of the B j can be readily calculated for some simple laminates and can be calculated without significant difficulty for many more complex laminates. The influence of bending-extension coupling can be evaluated by use of the reduced bending stiffness approximation suggested by Ashton [7-20]. If you examine the matrix manipulations for the inversion of the force-strain-curvature and moment-strain-curvature relations (see Section 4.4), you will find a definition that relates to the reduced bending stiffness approximation. You will find that you could use as the bending stiffness of the entire structure,... 

In spite of the fact that research on permanent waving has decreased over the past several decades, significant findings have been made within the past 10 years. For example, Wortmann and Kure [1,2] have developed a model and recently extended it to show that the bending stiffness of reduced and oxidized fibers controls the permanent waving behavior of human hair and that the cuticle plays a role in permanent waving. Further, they have shown not only that the cuticle functions as a barrier to reduction but also that its stiffness may contribute to fiber set. 

Use a sharp pair of scissors to cut a section through the cup, and note the corrugations which increase the bending stiffness of the wall. The corrugations also provide grip and reduce heat transfer to the fingers. Note the variation in wall thickness. 

For products under a constant applied load, such strut collapse causes failure. The struts should be redesigned with L- or U-shaped cross sections to increase their bending stiffness. The introduction of diagonal cross-ribs (Chapter 13) reduces the effective length L of the struts, so increases the buckling load. For struts with L/d < 30, yielding occurs before the strut... 

Figure 3 shows that the bending stiffness of the bipartite beam with the optimized elastic adhesive layer will be reduced to about 80% of that of a classical glulam beam of the same size. 

It should be noted that moisture-induced degradation of the fiber/matrix interface could significantly reduce the stiffness of the FRP pipes when subjected to bending, shear and compression loading conditions, while the hoop strength would not be as significantly affected. This is because a debonded fiber/matrix interface acts mainly as interlaminar cracks, and therefore would induce less impact on the strength of the pipes, especially when subject to purely internal pressure. 

We close with two remarks. First, we also investigated the infiuence of defects on the lower part ofthe filament, where the bending stiffness ke Tip is strongly reduced, and found that they significantly increase the pumping performance [92]. Second, we studied the pumping performance of several filaments placed along the y-axis [79]. 

So far, we have only considered parallel-sided adherends in single- and double-lap joints. It has been shown that the mathematical treatment, whether it is by closed-form analytical methods or by finite-element techniques, is difficult if realistic results are to be obtained. For instance, it is essential to allow for adhesive and adherend plasticity if joint strength predictions are to be made. But, as shown in Fig. 5, there are several forms of the lap joint in which the adherends are not parallel-sided, constant-thickness sheets but can have a variety of forms. These deviants are an attempt to reduce the high stress and strain concentrations, which occur at the ends of the simple lap joint, by modifying the stiffness of the adherends. In these profiled joints, the load line direction must change and, in addition to the tensile stiffness, so the shear and bending stiffness of the adherends change. 

The bending stiffness of a homogeneous beam of material 1 is ,/. Thus, the effective bending stiffness of the sandwich beam has been reduced by the factor a, by replacing the core by material 2 with a lower modulus 2 but with a lower density P2. However, the stiffness-to-weight ratio has been increased as shown by Example 9.2. 

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