Flexural rigidity

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

Development of a high-density nonwoven structure to improve the stab resistance of protective clothing material.

Abstract: The purpose of this research was to enhance the stab resistance of protective clothing material by developing a new high-density nonwoven structure. Ice picks often injure Japanese police officers due to the strict regulation of swords in the country. Consequently, this study was designed to improve stab resistance against ice picks. Most existing anti-stab protective clothing research has focused on various fabrics impregnated with resin, an approach that brings with it problems of high cost and complicated processing. Seldom has research addressed the potential for improving stab resistance by using nonwoven structures, which exhibit better stab resistance than fabric. In this research, we prepared a series of nonwoven structures with densities ranging from about 0.14 g/cm3 to 0.46 g/cm3 by varying the number of stacked layers of Kevlar/polyester nonwoven under a hot press. We then proposed two methods for producing such hot-press nonwovens: the multilayer hot-press method and the monolayer hot-press method. Stab resistance was evaluated according to NIJ Standard-0115.00. We also investigated the relationship among nonwoven density, stab resistance, and flexural rigidity, and here we discuss the respective properties of the two proposed methods. Our results show that stab resistance and flexural rigidity increase with nonwoven density, but flexural rigidity of nonwovens prepared using the monolayer hot-press method only shows a slight change as nonwoven density increases. Though the two methods exhibit little difference in maximum load, the flexural rigidity of nonwovens prepared using the monolayer hot-press method is much lower, which contributes to superior wear comfort. Finally, we investigated the mechanism behind the stabbing process. Stabbing with an ice pick is a complicated process that involves many factors. Our findings indicate that nonwovens stop penetration primarily in two ways: nonwoven deformation and fiber fractures.

Yielding of Uniformly Loaded Steel Members

Abstract: Expressions are developed for the stiffness of a uniformly yielded steel member. Flexural stiffness is shown to be non-zero for all yielded configurations of the member, and thus non-zero buckling loads may be obtained. The stiffness expressions are developed by considering the discontinuous nature of the yielding of structural steel, and they are presented for later use in a buckling analysis of members in plastically designed steel frames.

Elasticity of polymer-anchored membranes

Abstract: The renormalization of the elastic constants of a polymer-anchored membrane is investigated by means of systematic Monte Carlo simulations. Our results indicate that when polymers are grafted on both sides, and are in the brush regime, the excess bending rigidity scales as N3σα (N and σ being the number of statistical segments and grafting density, respectively) with 7/3 < α < 5. When the membrane is grafted on one side only, the induced excess bending modulus depends on the bare membrane bending modulus, κ0, and approaches a value of (3/2)κ0. These results are largely in agreement with the self-consistent field theory and scaling arguments using the blob picture.

Effects of environment on the fatigue of graphite-epoxy composites

Abstract: Torsional and flexural fatigue tests were performed on both uniaxial (0 deg) and crossplied (plus or minus 45 deg) graphite-epoxy materials at temperatures of 24 and 74 C in environments of air and water. The results of the torsion testing showed that the number of cycles required to cause an initial decrease in stiffness as well as the rate of stiffness loss was a function of temperature and environment; the most significant losses were noted for tests at the higher temperature in water. The torsional fatigue specimens were subsequently tested in four-point bending to determine the effect of torsional damage on longitudinal properties. This damage caused changes in the flexural stiffness, failure stress, and failure energy, depending on the stress and environmental histories. The flexural fatigue tests also showed a significant effect of water (at 24 C) on the material behavior. These results are compared with the results of previous investigations and are discussed in terms of proposed damage mechanisms.

Nonlinear analysis of single reinforced concrete piles subjected to lateral loading

Abstract: This paper proposes a method for the nonlinear analysis of laterally loaded single reinforced concrete piles based on the beam-onnonlinear- Winkler-foundation approach. A nonlinear fiber beam-column element is used to model the nonlinear behavior of a pile. The pile is divided into a series of segments, of which the cross section is assumed to be plane and normal to the longitudinal axis. The internal force of a segment is derived by integrating the nonlinear stress-strain relationships of all steel and concrete fibers within the cross section of the segment. The substructure technique is introduced to calculate the stiffness matrix of the segments. The nonlinear behavior of soils surrounding the pile is characterized by a modified strain wedge model. The results show that (1) the predicted results using the proposed method are consistent with the measurements for all three full-scale tested piles, and (2) updating the neutral axis of segments has a significant effect on the calculated lateral deflection; however, it has a slight effect on the calculated bending moment. Moreover, an empirical equation is derived from the numerical analyses for estimating the cracked flexural rigidity of bored piles subjected to lateral loading.