Shear buckling

Vjrf = max. value of shear the design shear buckling. 

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For the shear buckling mode in Figure 3-55, the fiber displacements are equal and in phase with one another. The matrix material is alternately sheared in one direction and then the other as the x-direction is traversed. However, changes in deformation in the y-direction are ignored. Thus, the shear strains are presumed to be a function of the fiber-direction coordinate alone. The matrix is sheared according to... 

Fig. 18.4. a Schematic representations of selected helical parameters, characterizing the relative positions and orientations of bases within base pairs. From top Shear, buckle and propeller twist, b Schematic representations of selected helical parameters, characterizing the relative positions and orientations of base pairs. From top Displacement, roll and helical twist... 

P(6) The shear buckling resistance shall be verified as specified in 4.7.2. 

Cylinders subject to in-plane shear stresses can also fail in the elastic, inelastic, and plastic range. Though shear buckling is rarely a controlling factor in the design of... 

Tables and clauses related to shear buckling are given in Section 5.5.6 of the code. This is needed for which the shear failure mode is a consequence of buckling rather than yielding. Simple post critical method is a prominant one. Interaction of moment resistance and shear buckling is an important phenomenon which needs full checking. The following relations are to be noted...

Shear buckling of the vertical wall Where a squat silo (low aspect ratio) is either eccentrically filled (unsymmetrical top pile producing different heights of solid-wall contact) or is subjected to seismic excitation, the wall can buckle in shear near the foundation. These buckles have a characteristic diagonal stripe shape, but these load cases are relatively rare. 

Figure 3-55 Extensional Mode and Shear Mode of Fiber Buckling...

Rgure 3-59 Rber Deformations During Shear Mode Buckling... 

Dow and Rosen s results are plotted in another form, composite material strain at buckling versus fiber-volume fraction, in Figure 3-62. These results are Equation (3.137) for two values of the ratio of fiber Young s moduius to matrix shear modulus (Ef/Gm) at a matrix Poisson s ratio of. 25. As in the previous form of Dow and Rosen s results, the shear mode governs the composite material behavior for a wide range of fiber-volume fractions. Moreover, note that a factor of 2 change in the ratio Ef/G causes a factor of 2 change in the maximum composite material compressive strain. Thus, the importance of the matrix shear modulus reduction due to inelastic deformation is quite evident. 

Shear-stress-shear-strain curves typical of fiber-reinforced epoxy resins are quite nonlinear, but all other stress-strain curves are essentially linear. Hahn and Tsai [6-48] analyzed lamina behavior with this nonlinear deformation behavior. Hahn [6-49] extended the analysis to laminate behavior. Inelastic effects in micromechanics analyses were examined by Adams [6-50]. Jones and Morgan [6-51] developed an approach to treat nonlinearities in all stress-strain curves for a lamina of a metal-matrix or carbon-carbon composite material. Morgan and Jones extended the lamina analysis to laminate deformation analysis [6-52] and then to buckling of laminated plates [6-53]. 

In many cases, a product fails when the material begins to yield plastically. In a few cases, one may tolerate a small dimensional change and permit a static load that exceeds the yield strength. Actual fracture at the ultimate strength of the material would then constitute failure. The criterion for failure may be based on normal or shear stress in either case. Impact, creep and fatigue failures are the most common mode of failures. Other modes of failure include excessive elastic deflection or buckling. The actual failure mechanism may be quite complicated each failure theory is only an attempt to explain the failure mechanism for a given class of materials. In each case a safety factor is employed to eliminate failure. 

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