Axial tension of nonlinear elastic composite shells of zero Gaussian curvature with a rectangular hole

The formulation of physically nonlinear problems for composite shells of zero Gaussian curvature weakened by a rectangular hole under the action of axial loading is given. The initial equations are the equations of the theory of non-sloping shells, in which the Kirchhoff–Love hypotheses take place. Geometric relationships are written in vector form, and physical relationships are based on the deformation theory of plasticity for anisotropic materials. The system of resolving equations is obtained from the Lagrange variational principle. A technique has been developed for the numerical solution of two-dimensional physically nonlinear problems for orthotropic composite shells of this type, based on the use of the method of additional stresses and the method of finite elements. A variant of the finite element method is proposed, the peculiarity of which lies in the vector approximation of the sought values and the discrete execution of the geometric part of the Kirchhoff–Love hypotheses (at the nodes of finite elements). Using the developed technique, the nonlinear elastic state of an organoplastic conical shell with a rectangular hole, which at the ends is reinforced with frames and loaded with uniformly distributed tensile forces, has been investigated.

Experimental Study of Hollow Slender Reinforced Concrete Columns Subjected to Eccentric Loads

This paper was focused on the investigating on the behavior of hollow slender reinforced concrete columns subjected to the axial loads. A total of seven specimens were designed as slender reinforced columns and these were divided into two groups. Each column is symmetrical and had a rectangular cross section of 140 × 80 mm and 2000 mm in length. The column was reinforced by 6Ø6mm for longitudinal reinforcement and Ø6@6 mm bars were used for transverse reinforcement ties. The effect of strengthening by CFRP sheet on the buckling of column, eccentricity 20, 40 and 120 mm and opening shape were studied. The results showed that the strengthened columns by CFRP caused an in the ultimate load CFRP were 26.3 % and 76.3 % for strengthened lengths of L/4 and L respectively compared with the un-strengthened column. The ultimate load of columns is reduced with existing the load eccentricity and amount of losses in strength increased with increasing the eccentricity. Also, it was found the hollow columns having circular holes had better performance compared to hollow columns having rectangular hole

Mutual Influence of Geometric Parameters and Mechanical Properties on Thermal Stresses in Composite Laminated Plates with Rectangular Holes

In this research, the mutual influence of the mechanical properties and geometric parameters on thermal stress distribution in symmetric composite plates with a quasi-rectangular hole subjected to uniform heat flux is examined analytically using the complex variable technique. The analytical solution is obtained based on the thermo-elastic theory and the Lekhnitskii’s method. Furthermore, by employing a suitable mapping function, the solution of symmetric laminates containing a circular hole is extended to the quasi-rectangular hole. The effect of important parameters including the stacking sequence of laminates, the angular position, the bluntness, and the aspect ratio of the hole and the flux angle in the stacking sequence of [45/−45]s for composite materials are examined in relation to the thermal stress distribution. The thermal insulated state and Neumann boundary conditions at the hole edge are taken into account. It is found out that the hole rotation angles and heat flux angle play key roles in obtaining the optimum thermal stress distribution around the hole. The present analytical method can well investigate the interaction of effective parameters on symmetric multilayer composites under heat flux.

Multi-band terahertz superabsorbers based on perforated square-patch metamaterials

This paper presents a multi-band terahertz superabsorber with a surface structure that consists of a square metallic patch with a very small rectangular hole whose area is only 3.94% of the square patch.

Frequency Reconfigurable Compact Antenna for Multiband Wireless Communication Application

This pioneering work suggests a reconfigurable multiband frequency antenna for applications in wireless networking The miniaturization and multi-band function of the mounted antenna is done by inserting a rectangular hole, and the reconfiguration of the frequency is achieved by utilizing two PIN diode switches. The ON and OFF state of the PIN diode determines the surface current distribution of the radiating patch resulting in the multiband resonance and reconfiguration of the proposed device. Application and analysis dependent on parameter of the antenna such as lack of return loss, VSWR, gain, and radiation pattern. The developed antenna is used for the intended application of wireless communication. Simulation is performed using Ansys HFSS.