Search results for "Strength of materials"

Strength and strain capacities of concrete compression members reinforced with FRP

2003

The analytical compressive behavior of concrete members reinforced with fiber-reinforced polymer (FRP) was examined. The variation in the shape of the transverse cross-section was analyzed. The bearing capacity and the increase in the maximum strain for members having a cross-section which was circular, square or square with round corners reinforced with FRP were determined. The proposed analytical model allows one to evaluate the confining pressure in ultimate conditions considering the effective confined cross-section and also allows one to determine the ultimate strain corresponding to FRP failure through a simplified energetic approach. Analytical results are then compared to experiment…

EXPERIMENTAL AND NUMERICAL EVALUATION OF THE MECHANICAL BEHAVIOUR OF GFRP SANDWICH PANELS

2007

This work deals with the analysis of the mechanical behaviour of a class of sandwich structures widely employed in marine constructions, constituted by fiber-glass laminate skins over PVC foam or polyester mat cores. In detail, a systematic experimental study and numerical simulations have shown that the theoretical prediction of the strength and the actual failure mechanism of these sandwich structures can be affected by significant errors, specially in the presence of prevalent shear loading. Moreover, because of the low shear stiffness and the elastic constants mismatch of the skins and core material, failure modes and strength are strongly influenced by eventual stresses orthogonal to t…

Shear-to-Moment Interaction in Glass Beams with Open Cross Sections

2018

An experimental investigation regarding the flexural behavior of glass beams with a length of 1,200 mm and rectangular, T-shaped, or I-shaped cross sections is presented and discussed. T-shaped and I-shaped cross sections were obtained by assembling laminated glass (LG) panels of 200 mm depth and 12.76 mm thickness through an acrylic adhesive. Three specimens for each series investigated were tested in flexure, focusing on the flexural and shear response of beams through the determination of the load-deflection curves and crack patterns at rupture. The shear span to depth ratio a/d was 2.25, which is a very low value, and interaction of shear and bending moment occurred during the tests. An…

Influence of FRP wrapping techniques on the compressive behavior of concrete prisms

2006

Abstract Results of an experimental investigation on the compressive behavior of concrete prisms with square cross-section, externally wrapped with carbon fiber reinforced plastic (CFRP) sheets are presented. The effects of the following parameters were analyzed: local reinforcement at the corners and continuous layers; horizontal and vertical discontinuous strips; number of continuous layers—length of specimens. An analytical model is proposed to determine the maximum bearing capacity of compressed concrete members with square cross-section and externally wrapped with FRP for the different configurations examined, and also able to consider the strength reduction with the length increase of…

A Digital Control System for the Hydraulic Fatigue Stand SHM 250b

2006

Unreliable and inflexible analog control systems of fatigue test stands applied in laboratories are being replaced by systems enabling easy development and implementation of new test ideas. This paper presents a digital control system applied in the fatigue test stand SHM 250b. It is based on a new electronic system and the I/O board RT-DAQ4/PCI with the software Matlab/Simulink used for communication with the board. The control system for the fatigue test stand SHM 250b gives the possibility of performing fatigue tests under controlled strain ε(t), stress σ(t) and energy parameter W(t) which is calculated from the stress and strain signals. The applied control system is now used, depending…

Micro-cracking of brittle polycrystalline materials with initial damage

2016

In this paper, the effect of pre-existing damage on brittle micro-cracking of polycrystalline materials is explored. The behaviour of single and multiple cracks randomly distributed within a grain scale polycrystalline aggregate is investigated using a recently developed grain boundary 3D computational framework. Each grain is modelled as a single crystal anisotropic domain. Opening, sliding and/or contact at grain boundaries are modelled using nonlinear cohesive-frictional laws. The polycrystalline micro-morphologies are generated using Voronoi tessellation algorithms in combination with a regularisation scheme to avoid the presence of unnecessary small geometrical entities (edges and face…

Stiprības mācība: lekcijas

1942

Diffusion and outgassing of O<inf>2</inf> in amorphous SiO<inf>2</inf> silica nanoparticles with specific surface properties

2014

Finite fracture mechanics analysis of crack onset at a stress concentration in a UD glass/epoxy composite in off-axis tension

2010

The presence of stress concentrations at holes and notches is known to reduce the strength of composite materials. Due to complexity of the damage processes at a stress raiser in a composite, different modeling approaches have been developed, ranging from empirical point and average stress criteria to involved damage mechanics or cohesive zone-based models of failure. Finite fracture mechanics approach with a coupled stress and energy failure criterion, recently developed and applied mainly to cracking in homogeneous isotropic materials, allows predicting the appearance and propagation of a crack using material strength and toughness characteristics obtained from independent tests. The pres…

Multiscale modeling of polycrystalline materials: A boundary element approach to material degradation and fracture

2015

Abstract In this work, a two-scale approach to degradation and failure in polycrystalline materials is proposed. The formulation involves the engineering component level (macro-scale) and the material grain level (micro-scale). The macro-continuum is modeled using a three-dimensional boundary element formulation in which the presence of damage is formulated through an initial stress approach to account for the local softening in the neighborhood of points experiencing degradation at the micro-scale. The microscopic degradation is explicitly modeled by associating Representative Volume Elements (RVEs) to relevant points of the macro continuum, for representing the polycrystalline microstruct…