Numerical analysis and investigation of short- and long-term behavior of unidirectional composites

2017 ◽  
Vol 52 (5) ◽  
pp. 659-678
Author(s):  
Elias Dib ◽  
Jean François Caron ◽  
Wassim Raphael ◽  
Ioannis Stefanou ◽  
Fouad Kaddah
Keyword(s):  
Tensile Strength ◽  
Ultimate Tensile Strength ◽  
Fiber Strength ◽  
Fiber Type ◽  
Glass Fibers ◽  
Shear Lag ◽  
Unidirectional Composites ◽  
Long Term Behavior ◽  
Shear Lag Theory

This study gives a detailed analysis on estimating the ultimate tensile strength of unidirectional fiber reinforced composites and its creep behavior under sustained tension load. We develop two different micromechanical models that allow us to estimate the longitudinal tensile strength and the evolution with time of fiber and matrix stresses around arbitrary array of fiber breaks. The first model is based on the shear-lag theory while the second one is developed using the software Abaqus. The comparison of the above models allowed to validate the fundamental assumptions of the shear-lag theory (first model) as well as several numerical issues related to time integration and spatial discretization. The Monte–Carlo method was used in order to account for the stochastic fiber strength and its impact on the ultimate tensile strength (short-term) and creep (long-term behavior) of unidirectional composites. Finally, a parametric investigation on the fiber type and the load level on the long-term behavior of unidirectional composites was performed showing an accelerating creep effect for fibers of inferior quality such as glass fibers compared to carbon fibers.

Microstructure and Tensile Properties of a 1.25Cr-0.5Mo Main Steam Pipe After Long-Term Service

2018 ◽  
Author(s):  
Bin Yang ◽  
Wen-Chun Jiang ◽  
Wen-Qi Sun ◽  
Yan-Ling Zhao ◽  
Wei-Ya Zhang
Keyword(s):  
Tensile Strength ◽  
Ultimate Tensile Strength ◽  
Tensile Properties ◽  
Yield Stress ◽  
Tensile Deformation ◽  
High Yield ◽  
Micro Hardness ◽  
Steam Pipe ◽  
Main Steam

Metallographic tests, micro-hardness tests and tensile tests were conducted for a 1.25Cr-0.5Mo main steam pipe weldment served for more than 26 years. The results were compared with those for virgin material. Microstructural evolution of 1.25Cr-0.5Mo base metal was investigated. Degradation in micro-hardness and tensile properties were also studied. In addition, the tensile properties of subzones in the ex-service weldment were characterized by using miniature specimens. The results show that obvious microstructural changes including carbide coarsening, increasing inter lamella spacing and grain boundary precipitates take place after long-term service. Degradation in micro-hardness is not obvious. However, the effects of long term service on tensile deformation behavior, ultimate tensile strength and yield stress are remarkable. Based on the yield stress of micro-specimens, the order of different subzones is: WM > HAZ > BM, which is consistent with the order of different subzones based on micro-hardness. However, the ultimate tensile strength and fracture strain of HAZ are lower than BM. Brittle failures can happen more easily for HAZ due to its high yield ratio.

Long-Term Development of Strength of Cement Paste with Fly Ash

2016 ◽  
Vol 722 ◽  
pp. 151-156
Author(s):  
Ondřej Zobal ◽  
Pavel Padevět
Keyword(s):  
Tensile Strength ◽  
Fly Ash ◽  
Cement Paste ◽  
Concrete Structure ◽  
Concrete Mixture ◽  
Massive Concrete ◽  
Negative Impacts ◽  
Long Term Behavior

The paper deals with the long-term development of strength of cement paste with fly ash. If the fly ash replaces the clinker in the cement or concrete mixture, the properties of the fresh and hardened material are affected. The slower increase in the strength of concrete is one of the biggest negative impacts. However, there are applications where it does not matter - e.g. massive concrete structure. It is important due to the ever increasing requirement from society for saving material and energy and durability of structures monitoring long-term behavior of such modified material. Three different mixtures were made for this experiment - cement paste without fly ash and cement paste with replacement of 40 and 50% of cement by fly ash. The evaluation of the measurement of compressive and tensile strength after 28, 90, 180 days and 5 years is presented in this paper.

Relationship Between Mechanical Properties and Collagen Structure of Closed and Open Wounds

1988 ◽  
Vol 110 (4) ◽  
pp. 352-356 ◽  
Author(s):  
Charles J. Doillon ◽  
Michael G. Dunn ◽  
Frederick H. Silver
Keyword(s):  
Mechanical Properties ◽  
Tensile Strength ◽  
Ultimate Tensile Strength ◽  
Collagen Fiber ◽  
Fiber Diameter ◽  
Normal Skin ◽  
Collagen Fibers ◽  
Collagen Structure ◽  
Collagen Network

Mechanical properties and collagen structure of excisional wounds left open are compared with wounds closed by clips. In both wound models, collagen fiber diameter increases with time post-wounding and is related to tensile strength. Clipped wounds show a higher ultimate tensile strength and tangent modulus compared with open wounds. In clipped wounds, newly deposited collagen appears as a biaxially oriented network as observed in normal skin. In open wounds a delay in the organization of the collagen network is observed and parallel wavy-shaped ribbons of collagen fibers are deposited. At long term, the high extensibility observed in open wounds may be due to the sliding of ribbons of collagen fibers past each other.

The Effect of Shear Lag on Long-Term Behavior of Steel/Concrete Composite Beams

2011 ◽  
Vol 255-260 ◽  
pp. 1070-1076 ◽  
Author(s):  
Lin Miao ◽  
De Wei Chen
Keyword(s):  
Finite Element ◽  
Virtual Work ◽  
Current Model ◽  
Shear Lag ◽  
Shear Lag Effect ◽  
Viscoelastic Problem ◽  
Lag Effect ◽  
Effective Flange Width ◽  
Long Term Behavior

It is well known that shear lag effect exists in wide flange concrete slabs. Traditionally, the effective flange width method is employed for considering the shear lag effect in a steel/concrete composite beam. The limitation of this method is that the load types and constraint conditions are generally ignored. In this paper, an analytical method using full flange width has been proposed by introducing shear warping shape function and intensity function of the shear warping displacement. By mean of two unknown functions: the vertical displacement of the whole cross section and the intensity of the warping, a variational balance condition which involves equilibrium equations with relevant boundary condition is imposed by the virtual work theorem. As a result, the shear-lag effect is considered by additional virtual external load, expressed as “additional bending moment”. The performance of this method dealing with elastic problem has been verified by finite element method using solid elements. Finally, the method is applied to investigate the long-term behavior of a beam fixed at two ends. It has been found that the results yielded from the code based on the effective flange width method are intervenient between those obtained from the current model with elastic and viscoelastic problem; the result errors of beam finite element model considering shear-lag effect can be modified by the method proposed in this paper.

scholarly journals Bonded Orthodontic Retainer and Fixed Partial Denture Made with Fiber Reinforced Composite Resin

2011 ◽  
Vol 05 (02) ◽  
pp. 237-240 ◽  
Author(s):  
Ovul Kumbuloglu ◽  
Ahmet Saracoglu ◽  
Cenk Cura ◽  
Atilla User
Keyword(s):  
Tooth Movement ◽  
Glass Fibers ◽  
Orthodontic Tooth Movement ◽  
Fiber Reinforced ◽  
Partial Denture ◽  
Fiber Reinforced Composite ◽  
Fixed Partial Denture ◽  
Reinforced Composite ◽  
Long Term Behavior

ABSTRACTRetention is the phase of orthodontic treatment which maintains teeth in their orthodontically corrected positions, following the cessation of active orthodontic tooth movement. Development of resin-impregnated, fiber-reinforced composite materials has provided the potential to develop new approaches for stabilizing teeth and replacing teeth conservatively. This case report describes the rehabilitation of a patient with orthodontic and prosthetic problems. The long-term behavior of glass fibers splint must be evaluated in clinical studies. (Eur J Dent 2011;5:237-240)

Long-term evaluation of water sorption and ultimate tensile strength of HEMA-containing/-free one-step self-etch adhesives

2011 ◽  
Vol 39 (7) ◽  
pp. 506-512 ◽  
Author(s):  
Masahiro Takahashi ◽  
Masatoshi Nakajima ◽  
Keiichi Hosaka ◽  
Masaomi Ikeda ◽  
Richard M. Foxton ◽  
...  
Keyword(s):  
Tensile Strength ◽  
Ultimate Tensile Strength ◽  
Water Sorption ◽  
Term Evaluation ◽  
One Step ◽  
Self Etch

scholarly journals Long-term Test Arrangement for Externally Strengthened Reinforced Concrete Elements

10.14311/452 ◽  
2003 ◽  
Vol 43 (4) ◽  
Author(s):  
T. Vaňura ◽  
P. Štěpánek ◽  
I. Švaříčková ◽  
J. Adámek
Keyword(s):  
Epoxy Resin ◽  
Epoxy Resins ◽  
Glass Fibers ◽  
High Strength ◽  
Space Saving ◽  
External Strengthening ◽  
Long Term Behavior ◽  
Concrete Elements ◽  
Special Space

Methods for external strengthening of concrete use elements of very high tensional strength glued on to its tensioned surface. These elements may be of metal, carbon fibers (CFRP), glass fibers or others, usually having very good mechanical properties. However, these high-strength elements are normally attached to concrete by epoxy resins. Epoxy resins have a low Young`s modulus and therefore a higher rate of creep may have an influence on the long-term behavior of such external strengthening. In order to verify this idea experimentally a special space-saving arrangement of tests is described in this paper. Panels act as loaded beams but simultaneously as a load for the other panels in a stand. The different load magnitude acting on a different layer of panels should make it possible to study the long-term influence of the degree of shear force on the glue creep. Certainly, the glue creep may be dependent on the type of epoxy resin; therefore several epoxy resin types are included in the tests.

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