Stress-relaxation behavior of fiber-reinforced polymer sheets at elevated temperatures

2021 ◽  
Vol 307 ◽  
pp. 124900
Author(s):  
Mohammad Houshmand Khaneghahi ◽  
Ali Kamyab Ghamsari ◽  
Togay Ozbakkaloglu
Keyword(s):  
Stress Relaxation ◽  
Elevated Temperatures ◽  
Relaxation Behavior ◽  
Fiber Reinforced Polymer ◽  
Fiber Reinforced ◽  
Stress Relaxation Behavior ◽  
Reinforced Polymer ◽  
Polymer Sheets

scholarly journals Interrelation between Fiber–Matrix Interphasial Phenomena and Flexural Stress Relaxation Behavior of a Glass Fiber–Polymer Composite

Polymers ◽  
2021 ◽  
Vol 13 (6) ◽  
pp. 978
Author(s):  
George C. Papanicolaou ◽  
Diana V. Portan ◽  
Lykourgos C. Kontaxis
Keyword(s):  
Stress Relaxation ◽  
Glass Fiber ◽  
Radial Distance ◽  
Relaxation Behavior ◽  
Fiber Reinforced Polymer ◽  
Time Dependent ◽  
Stress Relaxation Behavior ◽  
Reinforced Polymer ◽  
Fiber Matrix ◽  
Fiber Interaction

The response of fiber-reinforced polymer composites to an externally applied mechanical excitation is closely related to the microscopic stress transfer mechanisms taking place in the fiber–matrix interphasial region. In particular, in the case of viscoelastic responses, these mechanisms are time dependent. Defining the interphase thickness as the maximum radial distance from the fiber surface where a specific matrix property is affected by the fiber presence, it is important to study its variation with time. In the present investigation, the stress relaxation behavior of a glass fiber-reinforced polymer (GFRP) under flexural conditions was studied. Next, applying the hybrid viscoelastic interphase model (HVIM), developed by the first author, the interphase modulus and interphase thickness were both evaluated, and their variation with time during the stress relaxation test was plotted. It was found that the interphase modulus decreases with the radial distance, being always higher than the bulk matrix modulus. In addition, the interphase thickness increases with time, showing that during stress relaxation, fiber–matrix debonding takes place. Finally, the effect of fiber interaction on the interphase modulus was found. It is observed that fiber interaction depends on both the fiber–matrix degree of adhesion as well as the fiber volume fraction and the time-dependent interphase modulus.

Improving the impact resistance of concrete panels by glass fiber reinforced polymer sheets

2017 ◽  
Vol 8 (2) ◽  
pp. 304-320 ◽  
Author(s):  
Mohamed MA Abdel-Kader ◽  
Ahmed Fouda
Keyword(s):  
Glass Fiber ◽  
Plain Concrete ◽  
Fiber Reinforced Polymer ◽  
Fiber Reinforced ◽  
Glass Fiber Reinforced Polymer ◽  
Concrete Panels ◽  
Reinforced Polymer ◽  
Glass Fiber Reinforced ◽  
Polymer Sheets ◽  
The Impact

In this article, the response of 12 plain concrete specimens to an impact of hard projectiles was examined in an experimental study. The tests were planned with an aim to observe the influence of using glass fiber reinforced polymer sheets to strengthen plain concrete panels on the performance of concrete under this type of loading. The main findings show that strengthening plain concrete panels with glass fiber reinforced polymer sheets showed satisfactory performance under the impact load; the glass fiber reinforced polymer sheets can be used for strengthening or upgrading concrete structures to improve their resistance against impact. Also, the location of the glass fiber reinforced polymer sheet affects the front and rear face craters.

Relaxation behavior of prestressing basalt fiber-reinforced polymer tendons considering anchorage slippage

2016 ◽  
Vol 51 (9) ◽  
pp. 1275-1284 ◽  
Author(s):  
Jianzhe Shi ◽  
Xin Wang ◽  
Huang Huang ◽  
Zhishen Wu
Keyword(s):  
Relaxation Rate ◽  
Basalt Fiber ◽  
Relaxation Behavior ◽  
Fiber Reinforced Polymer ◽  
Initial Stresses ◽  
Fiber Reinforced ◽  
Relaxation Rates ◽  
Reinforced Polymer ◽  
Relaxation Loss ◽  
Basalt Fiber Reinforced Polymer

Relaxation is a key factor that controls the application of prestressing fiber-reinforced polymer tendons. This paper focuses on the evaluation of the relaxation behavior of newly developed basalt fiber-reinforced polymer tendons through an approach considering anchorage slippage. A series of relaxation tests on basalt fiber-reinforced polymer tendons subjected to three levels of initial stresses (0.4 fu, 0.5 fu, and 0.6 fu, where fu = ultimate strength) were conducted using a specially designed test setup that eliminates the impact of slippage at the anchor zone. An additional group of tests was conducted to validate the enhancement effect of pretension on the relaxation behavior. The relaxation rates at one million hours were predicted based on experimental fitting. Finally, the relaxation rates at 1000 h were predicted using the correlation between the relaxation and creep and were validated with the experimental relaxation rates. The results demonstrate the effectiveness of the proposed setup in measuring the relaxation loss of specimens and reveal that the relaxation rates of untreated basalt fiber-reinforced polymer tendons at 1000 h are 4.2%, 5.3%, and 6.4% at 0.4 fu, 0.5 fu, and 0.6 fu, respectively. Pretension treatment performs effective in relaxation loss controlling. BFRP tendons are recommended to be applied at an initial stress of 0.5 fu after pretension treatment, with one-million-hour relaxation rate equal to 6.7%. Furthermore, the relaxation rate at 1000 h can be predicted accurately based on the creep behavior. The conclusions of this study can provide guidance for the prestressing applications of basalt fiber-reinforced polymer tendons.

scholarly journals Experimental investigation of the microstructures and tensile properties of polyacrylonitrile-based carbon fibers exposed to elevated temperatures in air

2019 ◽  
Vol 14 ◽  
pp. 155892501985001 ◽  
Author(s):  
Chenggao Li ◽  
Guijun Xian
Keyword(s):  
Tensile Strength ◽  
Carbon Fiber ◽  
Carbon Fibers ◽  
Elevated Temperatures ◽  
Tensile Modulus ◽  
Fiber Reinforced Polymer ◽  
Carbon Fiber Reinforced Polymer ◽  
Fiber Reinforced ◽  
Reinforced Polymer ◽  
Carbon Fiber Reinforced

The elevated temperature resistance and even fire resistance of carbon fiber-reinforced polymer composites were critical concerns in many applications. These properties of a carbon fiber-reinforced polymer depend not only on the degradation of the polymer matrix but also on that of the carbon fibers under elevated temperatures. In this study, influences of elevated temperatures (by 700°C for 30 min) in air on the mechanical properties and microstructures of a carbon fiber were investigated experimentally. It was found that the tensile strength and modulus as well as the diameters of the carbon fibers were reduced remarkably when the treatment temperatures exceeded 500°C. At the same time, the content of the structurally ordered carbonaceous components on the surface of carbon fibers and the graphite microcrystal size were reduced, while the graphite interlayer spacing ( d002) was enhanced. The deteriorated tensile modulus was attributed to the reduced graphite microcrystal size and the reduced thickness of the skin layer of the carbon fiber, while the degraded tensile strength was mainly attributed to the weakened cross-linking between the graphite planes.

scholarly journals Water Absorption, Hydrothermal Expansion, and Thermomechanical Properties of a Vinylester Resin for Fiber-Reinforced Polymer Composites Subjected to Water or Alkaline Solution Immersion

Polymers ◽  
2019 ◽  
Vol 11 (3) ◽  
pp. 505 ◽  
Author(s):  
Xiaoli Yin ◽  
Yancong Liu ◽  
Yufei Miao ◽  
Guijun Xian
Keyword(s):  
Water Uptake ◽  
Alkaline Solution ◽  
Elevated Temperatures ◽  
Water Immersion ◽  
Thermomechanical Properties ◽  
Fiber Reinforced Polymer ◽  
Molecular Networks ◽  
Resin Matrix ◽  
Fiber Reinforced ◽  
Reinforced Polymer

In the present paper, a vinyl ester (VE) resin, potentially used as a resin matrix for fiber-reinforced polymer (FRP) composite sucker rods in oil drilling, FRP bridge cables, or FRP marine structures, was investigated on its resistance to water and alkaline solution immersion in terms of water uptake, hydrothermal expansion, and mechanical properties. A two-stage diffusion model was applied to simulate the water uptake processes. Alkaline solution immersion led to a slightly higher mass loss (approx. 0.4%) compared to water immersion (approx. 0.23%) due to the hydrolysis and leaching of uncured small molecules (e.g., styrene). Water immersion caused the expansion of VE plates monitored with Fiber Bragg Grating (FBG). With the same water uptake, the expansion increased with immersion temperatures, which is attributed to the increased relaxation extent of the resin molecular networks. Although an obvious decrease of the glass transition temperatures (Tg) of VE due to water immersion (5.4 to 6.1 °C/1% water uptake), Tg can be recovered almost completely after drying. Tensile test results indicate that a short-term immersion (less than 6 months) enhances both the strength and elongation at break, while the extension of the immersion time degrades both the strength and elongation. The modulus of VE shows insensitive to the immersion even at elevated temperatures.

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