Axial-flexural coupled vibration and buckling of composite beams using sinusoidal shear deformation theory

A finite element model based on sinusoidal shear deformation theory is developed to study vibration and buckling analysis of composite beams with arbitrary lay-ups. This theory satisfies the zero traction boundary conditions on the top and bottom surfaces of beam without using shear correction factors. Besides, it has strong similarity with Euler–Bernoulli beam theory in some aspects such as governing equations, boundary conditions, and stress resultant expressions. By using Hamilton’s principle, governing equations of motion are derived. A displacement-based one-dimensional finite element model is developed to solve the problem. Numerical results for cross-ply and angle-ply composite beams are obtained as special cases and are compared with other solutions available in the literature. A variety of parametric studies are conducted to demonstrate the effect of fiber orientation and modulus ratio on the natural frequencies, critical buckling loads, and load-frequency curves as well as corresponding mode shapes of composite beams

Theoretical and Single Crystal ESR Study of a (RSSH)^.- Species

The radical anion (Ph₃CSSH).- has been trapped at low temperature in an X-irradiated single crystal of (triphenylmethyl) disulfane. The g and ¹H hyperfine tensors are obtained and their eigenvectors are compared with the crystallographic bond directions. The optimized geometries for CH₃SSH, HSSH.-, and (CH₃SSH).- are obtained from ab initio calculations (6-31G* basis set). The theoretical ¹H anisotropic coupling tensors, obtained by evaluating the expectation value of the dipolar operator for (CH₃SSH).-, are compared with the present experimental values (for the S-H proton) and with recent literature data (for the proton bound to the carbon atom)