Flexural rigidity

About: Flexural rigidity is a research topic. Over the lifetime, 3829 publications have been published within this topic receiving 56780 citations.

Bending of sandwich beams with transversely flexible core

Abstract: The bending behavior of a sandwich beam with a foam core is analytically investigated. The beam consists of upper and lower skins, metallic or composite laminated, and a soft core. The loading pattern consists of concentrated as well as distributed loads exerted at the upper or the lower skin or a combination of the two. The analysis includes the effects of the flexibility of the core in the vertical direction on the overall bending behavior. The main parameters affecting the overall behavior and particularly the peeling and the shear stresses between the skins and the core are studied. ANDWICH beams have been used in various industries for many years. A typical beam consists of two skins made of metal or laminated composite and a core. The core is usually made of honeycomb, metallic or nonmetallic, which is stiff in the vertical direction and flexible in the horizontal one. In recent years, plastic foams are used for cores in sandwich structures. In this case, the effect of the transverse flexibility of the core on the mechanical behavior of the beam should be taken into account. This flexibility affects the transverse bend- ing behavior of the beam and leads to unequal deflections of the upper and lower symmetrical skins (see Fig. 1). Sandwich beams with honeycomb cores were considered by many researchers. Reissner1'2 included the shear strain effect on the bending, but only the average bending behavior of the composite beam is considered. Many researchers3'5 dealt with the analysis of beams with an antiplane core, i.e., a core with shear rigidity only. The Hexcel designer manual6 outlines the design procedures for beams with honeycomb cores only. An antiplane-cor e approach with anisotropic and composite skin appears in Refs. 7-9. Ojalvo10 assumed different deflec- tions to the two skins, but neglected the peeling stresses. Ogorkiewicz and Sayigh11 dealt with a foam core by replacing it with an ordinary beam with equivalent properties. In this paper, the proposed analysis includes the effects of the transverse flexibility of the core and the peeling stresses between the skin face and the core on the overall bending behavior. The analysis is general and applicable to metallic or com- posite laminated identical skins. The behavior is described in terms of the deflections, the peeling, and the shear stresses in the adhesive layers. The effect of the variables that govern the behavior is incorporated through a parametric study. The mathematical formulation and the boundary conditions are discussed. The analytical solution for the various types of loading with different boundary conditions is presented.

Sound transmission loss characteristics of sandwich panel constructions

Abstract: The sound transmission loss (TL) characteristics of panel constructions with thin face sheets and a thicker, lighter core are investigated. Analytical models of TL are developed for constructions with isotropic and orthotropic core materials. The occurrence of acoustic coincidence is described for symmetric and antisymmetric modes of propagation, in the panel. Symmetric propagation involves thickness deformation of the core, while antisymmetric propagation involves a bending deformation of the panel without thickness deformation. For symmetric modes, coincidence occurs near the conventional double wall resonance frequency characterized by the stiffness of the core and the mass of the face sheets, and also at higher frequencies associated with bending wave propagation in the face sheets. Antisymmetric modes account for shear deformation in the core, which results in a softening of the bending rigidity of the panel at higher frequencies. For orthotropic core materials, the acoustic behavior is dependent on ...

Deformation behavior of fiber-reinforced polymer reinforced engineered cementitious composite (ecc) flexural members under reversed cyclic loading conditions

Abstract: Research provided herein studies the response of fiber-reinforced polymer (FRP) reinforced engineered cementitious composite (ECC) members, focusing on flexural load-deformation behavior, residual deflection, damage evolution, and failure mode. Critical aspects of conventional FRP-reinforced concrete members are reviewed and compared to FRP reinforced ECC. The interaction of linear FRP reinforcement and ECC matrix with ductile stress-strain behavior in tension results in nonlinear elastic flexural response characteristics with stable hysteretic behavior, small residual deflection, and ultimately gradual compression failure. Compatible deformations of reinforcement and matrix lead to low interfacial bond stress and prevent composite disintegration by bond splitting and cover spalling. Flexural stiffness and strength as well as crack formation and widths in FRP-reinforced ECC members are found effectively independent of interfacial bond properties due to the tensile deformation characteristics of the cementitious matrix. A model for the load-deflection envelope based on a nonlinear moment-curvature relationship is suggested.

47—cloth stiffness and hysteresis in bending

Abstract: The relation between cloth flexural rigidity and single-fibre flexural rigidity is discussed, and a mathematical formula is derived for the minimum cloth flexural rigidity, neglecting interactions between the fibres; this formula takes account of the twist and crimp in the yarns. An instrument is described which enables the hysteresis in bending of a fabric to be studied; this is of assistance in interpreting the nature of the interactions between fibres, which cause the observed cloth flexural rigidity to exceed the theoretical minimum. The results are given of a detailed study of the bending behaviour of two fabrics; the effect of heat-setting these fabrics is examined.