Spelling suggestions: "subject:"[een] MACRO SYNTHETIC FIBER"" "subject:"[enn] MACRO SYNTHETIC FIBER""
1 |
[pt] COMPORTAMENTO DE ARRANCAMENTO EM CURTA E LONGA DURAÇÃO DE MACRO FIBRAS SINTÉTICAS / [en] SHORT- AND LONG-TERM PULLOUT BEHAVIOR OF MACRO SYNTHETIC FIBERSTHAIS DA SILVA ROCHA 19 August 2024 (has links)
[pt] O fenômeno de fluência em compósitos reforçados com fibras é
particularmente importante quando são utilizadas macro fibras sintéticas, que
devido ao seu baixo módulo de elasticidade, apresentam comportamento
viscoelástico pronunciado mesmo em temperatura ambiente, o que pode levar a
alterações no controle de fissuração ao longo do tempo. Testes de arrancamento são
comumente usados para prever interações fibra-matriz e neste trabalho foram
realizados para cargas de curto e longo prazo em três tipos de macro fibras
sintéticas. Diferentes níveis de cargas de longo prazo (20, 30, 40 e 50 por cento da carga
máxima de arrancamento em curta duração) e ângulos de orientação das fibras (15 graus celsius, 30 graus celsius e 45 graus celsius) em relação à direção da carga foram considerados para investigar a
influência desses parâmetros na interação entre macro fibras sintéticas e matriz.
Macro fibras com superfícies onduladas e maior módulo de elasticidade alcançaram
maiores tensões de aderência e menores deformações por fluência. Em testes de
curto prazo, imagens de microscopia óptica foram obtidas nas fibras arrancadas
para correlacionar a degradação superficial das fibras com as curvas de tensão
versus deformação. No arrancamento quase estático (curto prazo), foram
observadas pequenas reduções na resistência ao arrancamento à medida que o
ângulo foi aumentado para todas as fibras, além de uma intensa degradação de suas
superfícies devido ao significativo efeito de polia. Em contraste, para os testes de
longo prazo, foi observada uma redução da fluência com o aumento do ângulo de
inclinação da fibra causada pela redução da fluência da fibra devido ao
carregamento não axial e componentes de força adicionais produzidos pelo desvio
da força axial. O modelo viscoelástico de Burgers foi aplicado e apresentou boa
concordância com as curvas de fluência experimentais, consistindo, portanto, em
uma alternativa promissora para modelar o comportamento de longo prazo de fibras
individuais. Imagens de microtomografia e microscopia eletrônica de varredura
mostraram que uma parte da deformação em tração, sob carga sustentada, pode ser
atribuída à fluência da própria fibra, tornando desafiador estimar a fluência deste
tipo de compósito, dada a considerável variabilidade de configurações de fibra. / [en] The creep phenomenon in fiber-reinforced composites is particularly
important when macro synthetic fibers are used, due to their low modulus of
elasticity, exhibit pronounced viscoelastic behavior even at room temperature,
which can lead to changes in the cracking control over time. Pullout tests are
commonly used to predict fiber–matrix interactions and in this work were
conducted for short- and long-term on three types of polymeric macro fibers.
Different levels of long-term loads (20, 30, 40 and 50 percent of the maximum short-term
pullout load) and fiber orientation angles (15 degrees celsius, 30 degrees celsius, and 45 degrees celsius) with respect to the
direction of the load were considered to investigate the influence of these
parameters on the interaction between macro synthetic fibers and matrix. Macro
fibers with crimped surfaces and higher modulus of elasticity achieved higher bond
stresses and lower creep deformations. In short-term tests, optical microscopy
images were obtained on the pulled-out fibers to correlate the surface degradation
of the fibers with the stress versus strain curves. In quasi-static pullout (short-term),
small reductions in pullout strength were observed for all fibers and angles, in
addition to an intensive degradation of their surfaces owing to the significant
snubbing effect of this type of fiber. In contrast, for the long-term tests, a creep
reduction was observed with increasing fiber inclination angle caused by the creep
reduction of the fiber due to non-axial loading and additional force components
produced by the deviation of the axial force. The Burgers viscoelastic model was
applied and showed good agreement with the experimental creep curves, therefore
consisting of a promising alternative for modeling the long-term behavior of
individual fibers. Microtomography and scanning electron microscopy images
showed that a large portion of the strain in tension, under sustained load, can be
attributed to the creep of the fiber itself, thus making it challenging to estimate the
creep of this type of composite, given the considerable variability of fiber
configurations.
|
2 |
Use of non-steel fiber reinforcement in concrete tunnel liningSeo, Sang Yeon 26 January 2011 (has links)
Fiber reinforcement is being widely used in concrete tunnel linings these days. Using fiber reinforcement can save not only cost, but also labor and time spent on construction. However, many owners hesitate to incorporate fiber reinforcement in tunnel lining due to lack of experience with and knowledge of the behavior of fiber reinforced concrete (FRC)
In this study, fiber reinforced concrete was made with various kinds of fibers such as steel fiber, macro-synthetic fiber and hybrid fiber (a blend of macro-synthetic fiber and glass fiber). Many experimental tests were performed to investigate the compressive, flexural and shear behavior of fiber reinforced concrete. In addition to the structural capacity of FRC, the distribution of fiber reinforcement inside the concrete matrix was investigated. Test results of these experimental tests were thoroughly examined to compare and quantify the effects of fiber reinforcement. Next, the test results were used to generate axial force-bending moment interaction diagrams based on current design approaches. In addition, the current design approaches were modified to estimate the accurate and exact value of bending moment. Fiber reinforcement clearly improved the structural performance of tunnel lining. The post-peak flexural and shear strength was significantly influenced by the type and amount of fiber reinforcement. / text
|
Page generated in 0.0519 seconds