scholarly journals Accelerated Aging Behavior in Alkaline Environments of GFRP Reinforcing Bars and Their Bond with Concrete

Materials ◽  
2021 ◽  
Vol 14 (19) ◽  
pp. 5700
Author(s):  
Arnaud Rolland ◽  
Karim Benzarti ◽  
Marc Quiertant ◽  
Sylvain Chataigner
Keyword(s):  
Alkaline Solution ◽  
Glass Fibers ◽  
Accelerated Aging ◽  
Initial Increase ◽  
Reinforcing Bars ◽  
Scanning Calorimetry ◽  
Pull Out ◽  
Different Temperatures ◽  
Effects Of Aging ◽  
Direct Immersion

This study investigates the durability of glass fiber-reinforced polymer (GFRP) reinforcing bars (rebars) and their bond in concrete. Accelerated aging tests were first conducted on bare rebars that were either subjected to direct immersion in an alkaline solution or previously embedded in concrete before immersion in the solution (indirect immersion). Accelerated aging was conducted at different temperatures of the solution (20 °C, 40 °C and 60 °C) and for various periods up to 240 days. Residual tensile properties were determined for rebars subjected to direct immersion and served as input data of a predictive Arrhenius model. A large decrease in the residual tensile strength assigned to the alkali-attack of glass fibers was extrapolated in the long term, suggesting that direct immersion is very severe compared to actual service conditions. Short-beam tests were also performed on rebars conditioned under direct/indirect immersion conditions, but did not reveal any significant evolution of the interlaminar shear strength (ILSS). In a second part, bond tests were performed on pull-out specimens after immersion in the alkaline solution at different temperatures, in order to assess possible changes in the concrete/GFRP bond properties over aging. Results showed antagonistic effects, with an initial increase in bond strength assigned to a confinement effect of the rebar resulting from changes in the concrete properties over aging, followed by a decreasing trend possibly resulting from interfacial degradation. Complementary characterizations by scanning electron microscopy (SEM), differential scanning calorimetry (DSC) and Fourier transform infrared (FTIR) spectroscopy were also carried out to evaluate the effects of aging on the physical/microstructural properties of GFRPs.

Mechanical properties of norbornene-based silane treated glass fiber reinforced polydicyclopentadiene composites manufactured by the S-RIM process

e-Polymers ◽  
2017 ◽  
Vol 17 (2) ◽  
pp. 159-166 ◽  
Author(s):  
Hyeong Min Yoo ◽  
Dong-Jun Kwon ◽  
Joung-Man Park ◽  
Sang Hyuk Yum ◽  
Woo Il Lee
Keyword(s):  
Mechanical Properties ◽  
Glass Fiber ◽  
Glass Fibers ◽  
Process Conditions ◽  
Fiber Reinforced ◽  
Scanning Calorimetry ◽  
Reaction Injection Molding ◽  
Structural Reaction Injection Molding ◽  
Pull Out ◽  
Glass Fiber Reinforced

AbstractA lab scale structural reaction injection molding (S-RIM) piece of equipment was designed and used to fabricate glass fiber reinforced polydicyclopentadiene (p-DCPD) composites for three different fiber contents. In order to obtain information regarding the optimal process temperature (>80°C) and the curing time (<30 s), differential scanning calorimetry (DSC) was used to investigate the curing behavior of DCPD resin under isothermal conditions. Further, a norbornene-based silane treatment was used to improve the interfacial adhesion between the glass fibers and DCPD as confirmed by the micro-droplet pull-out test and scanning electron microscopy (SEM). Fabrication of glass fiber/p-DCPD composites with improved mechanical properties was carried out based on the optimized process conditions and surface treatment of glass fiber.

scholarly journals The Influence of the Accelerated Aging Conditions on the Properties of Polyolefin Geogrids Used for Landfill Slope Reinforcement

Polymers ◽  
2020 ◽  
Vol 12 (9) ◽  
pp. 1874
Author(s):  
Agnieszka Kiersnowska ◽  
Wojciech Fabianowski ◽  
Eugeniusz Koda
Keyword(s):  
Mechanical Properties ◽  
Relative Elongation ◽  
Oxidative Degradation ◽  
Accelerated Aging ◽  
Melt Flow Index ◽  
Flow Index ◽  
Scanning Calorimetry ◽  
Oxidation Induction Time ◽  
Aging Test ◽  
Different Temperatures

Polyolefin geosynthetics are susceptible to oxidative degradation, which in turn leads to diminished mechanical properties in geotechnical constructions. When using these materials, it is extremely important to determine their durability over time in particularly aggressive conditions. In order to prolong the life of a geosynthetic material, antioxidants are added during the manufacturing process. The function of antioxidants is to prevent polymer oxidation reaction in time. As the antioxidant content is depleted, the polymer becomes less protected towards oxidative attacks. This article describes the aging process of uniaxial (high density polyethylene) HDPE geogrids under the influence of chemical and environmental factors. Evaluations of accelerated aging test of the uniaxial HDPE geogrids were incubated in simulated landfill conditions for a period of 12 months. Three temperatures (25 °C, 45 °C, and 75 °C) were selected for carrying out the aging experiments in aqueous solutions mimicking landfill conditions. The changes observed by differential scanning calorimetry (DSC), Fourier transform infrared spectroscopy (FTIR) and melt flow index (MFI) correlate with the mechanical properties of the aged geogrid. No significant changes in the FTIR and MFI were observed over the 12 months of accelerated aging tests at none of the three different temperatures. The oxidation induction time (OIT) test showed no antioxidant remaining in the geogrid following eight months of aging test at 75 °C. No significant changes in the influence of accelerated aging tests on the average relative elongation at 25 °C and 45 °C of the tested material were observed. Accelerated aging tests at 75 °C showed that the mean elongation of 12.12% for the sample not subjected to accelerated aging tests (new sample) increased to 19.32% (after 12 months of incubation).

scholarly journals Dynamic Single-Fiber Pull-Out of Polypropylene Fibers Produced with Different Mechanical and Surface Properties for Concrete Reinforcement

Materials ◽  
2021 ◽  
Vol 14 (4) ◽  
pp. 722
Author(s):  
Enrico Wölfel ◽  
Harald Brünig ◽  
Iurie Curosu ◽  
Viktor Mechtcherine ◽  
Christina Scheffler
Keyword(s):  
Tensile Strength ◽  
Dynamic Loading ◽  
Melt Spinning ◽  
Structural Changes ◽  
High Surface ◽  
Single Fiber ◽  
Scanning Calorimetry ◽  
Matrix Interaction ◽  
Pull Out ◽  
Fiber Matrix

In strain-hardening cement-based composites (SHCC), polypropylene (PP) fibers are often used to provide ductility through micro crack-bridging, in particular when subjected to high loading rates. For the purposeful material design of SHCC, fundamental research is required to understand the failure mechanisms depending on the mechanical properties of the fibers and the fiber–matrix interaction. Hence, PP fibers with diameters between 10 and 30 µm, differing tensile strength levels and Young’s moduli, but also circular and trilobal cross-sections were produced using melt-spinning equipment. The structural changes induced by the drawing parameters during the spinning process and surface modification by sizing were assessed in single-fiber tensile experiments and differential scanning calorimetry (DSC) of the fiber material. Scanning electron microscopy (SEM), atomic force microscopy (AFM) and contact angle measurements were applied to determine the topographical and wetting properties of the fiber surface. The fiber–matrix interaction under quasi-static and dynamic loading was studied in single-fiber pull-out experiments (SFPO). The main findings of microscale characterization showed that increased fiber tensile strength in combination with enhanced mechanical interlocking caused by high surface roughness led to improved energy absorption under dynamic loading. Further enhancement could be observed in the change from a circular to a trilobal fiber cross-section.

scholarly journals Impact of Prolonged Exposure of Eleven Years to Hot Seawater on the Degradation of a Thermoset Composite

Polymers ◽  
2021 ◽  
Vol 13 (13) ◽  
pp. 2154
Author(s):  
Amir Hussain Idrisi ◽  
Abdel-Hamid I. Mourad ◽  
Muhammad M. Sherif
Keyword(s):  
Exposure Time ◽  
Prolonged Exposure ◽  
Mechanical Performance ◽  
Matrix Cracking ◽  
Pull Out ◽  
Strength Based ◽  
Different Temperatures ◽  
River Line ◽  
Composite Samples

This paper presents a long-term experimental investigation of E-glass/epoxy composites’ durability exposed to seawater at different temperatures. The thermoset composite samples were exposed to 23 °C, 45 °C and 65 °C seawater for a prolonged exposure time of 11 years. The mechanical performance as a function of exposure time was evaluated and a strength-based technique was used to assess the durability of the composites. The experimental results revealed that the tensile strength of E-glass/epoxy composite was reduced by 8.2%, 29.7%, and 54.4% after immersion in seawater for 11 years at 23 °C, 45 °C, and 65 °C, respectively. The prolonged immersion in seawater resulted in the plasticization and swelling in the composite. This accelerated the rate of debonding between the fibers and matrix. The failure analysis was conducted to investigate the failure mode of the samples. SEM micrographs illustrated a correlation between the fiber/matrix debonding, potholing, fiber pull-out, river line marks and matrix cracking with deterioration in the tensile characteristics of the thermoset composite.

Effects of additives on the cure kinetics of vinyl ester pultrusion resins

2021 ◽  
pp. 002199832110015
Author(s):  
Alexander Vedernikov ◽  
Yaroslav Nasonov ◽  
Roman Korotkov ◽  
Sergey Gusev ◽  
Iskander Akhatov ◽  
...  
Keyword(s):  
Vinyl Ester ◽  
Mean Squared Error ◽  
Cure Kinetics ◽  
Zinc Stearate ◽  
Heating Rates ◽  
Scanning Calorimetry ◽  
Different Temperatures ◽  
Predicted Values ◽  
Kinetics Of ◽  
Final Degree

Pultrusion is a highly efficient composite manufacturing process. To accurately describe pultrusion, an appropriate model of resin cure kinetics is required. In this study, we investigated cure kinetics modeling of a vinyl ester pultrusion resin (Atlac 430) in the presence of aluminum hydroxide (Al(OH)3) and zinc stearate (Zn(C18H35O2)2) as processing additives. Herein, four different resin compositions were studied: neat resin composition, composition with Al(OH)3, composition comprising Zn(C18H35O2)2, and composition containing both Al(OH)3 and Zn(C18H35O2)2. To analyze each composition, we performed differential scanning calorimetry at the heating rates of 5, 7.5, and 10 K/min. To characterize the cure kinetics of Atlac 430, 16 kinetic models were tested, and their performances were compared. The model based on the [Formula: see text]th-order autocatalytic reaction demonstrated the best results, with a 4.5% mean squared error (MSE) between the experimental and predicted data. This study proposes a method to reduce the MSE resulting from the simultaneous melting of Zn(C18H35O2)2. We were able to reduce the MSE by approximately 34%. Numerical simulations conducted at different temperatures and pulling speeds demonstrated a significant influence of resin composition on the pultrusion of a flat laminate profile. Simulation results obtained for the 600 mm long die block at different die temperatures (115, 120, 125, and 130 °C) showed that for a resin with a final degree of cure exceeding 95% at the die exit, the maximum difference between the predicted values of pulling speed for a specified set of compositions may exceed 1.7 times.

scholarly journals Effects of Aging under Stress on Mechanical Properties and Microstructure of EN AW 7075 Alloy

Metals ◽  
2021 ◽  
Vol 11 (7) ◽  
pp. 1142
Author(s):  
S. V. Sajadifar ◽  
P. Krooß ◽  
H. Fröck ◽  
B. Milkereit ◽  
O. Kessler ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Mechanical Properties ◽  
Screening Tool ◽  
Precipitation Kinetics ◽  
Scanning Calorimetry ◽  
Aging Precipitation ◽  
Precipitation Processes ◽  
External Stresses ◽  
7075 Alloy ◽  
Effects Of Aging

In the present study, microstructural and mechanical properties of EN AW 7075 following stress-aging were assessed. For this purpose, properties of stress-aged samples were compared with values obtained for conventionally aged counterparts. It is revealed that the strength and hardness of EN AW 7075 can be increased by the presence of external stresses during aging. Precipitation kinetics were found to be accelerated. The effects of conventional and stress-aging on the microstructure were analyzed using synergetic techniques: the differently aged samples were probed by differential scanning calorimetry (DSC) in order to characterize the precipitation processes. DSC was found to be an excellent screening tool for the analysis of precipitation processes during aging of this alloy with and without the presence of external stresses. Furthermore, using electron microscopy it was revealed that an improvement in mechanical properties can be correlated to changes in the morphologies and sizes of precipitates formed.

Degradation of VIP barrier envelopes exposed to alkaline solution at different temperatures

2015 ◽  
Vol 93 ◽  
pp. 208-216 ◽  
Author(s):  
Huiqiang Li ◽  
Huisu Chen ◽  
Xiangyu Li ◽  
Wenhui Duan
Keyword(s):  
Alkaline Solution ◽  
Different Temperatures

Estimation of Firing Temperature and Compositional Variability of Archaeological Pottery by Differential Scanning Calorimetry

2004 ◽  
Vol 852 ◽  
Author(s):  
A. Giordana ◽  
E. Peacock ◽  
M. McCarthy ◽  
K. Guilbeau ◽  
P. Jacobs ◽  
...  
Keyword(s):  
Firing Temperature ◽  
Thermal Characterization ◽  
Small Sample ◽  
Scanning Calorimetry ◽  
Blind Test ◽  
Vitrification Temperature ◽  
Archaeological Pottery ◽  
Digital Scanning ◽  
Different Temperatures ◽  
Upper Estimate

ABSTRACTDigital Scanning Calorimetry (DSC), a thermal characterization technique, can be used to rapidly obtain a rough upper estimate of the firing temperature of archaeological pottery as well as an indication of its composition. The technique involves heating a small sample (10–20 mg) of ground ceramic above the vitrification temperature, cooling and reheating. The curves of the two heating cycles are then compared. The validity of the technique was evaluated by a blind test in which 35 tiles fired at different temperatures were analyzed without knowing their firing point, and by analysis of archaeological pottery samples assumed to be local or imported based upon stylistic criteria.

Experimental Study on Bond Behavior of GFRP-to-Cement Mortar

2011 ◽  
Vol 94-96 ◽  
pp. 543-546
Author(s):  
Ning Zhang ◽  
Ai Zhong Lu ◽  
Yun Qian Xu ◽  
Pan Cui
Keyword(s):  
Aluminium Alloy ◽  
Cement Mortar ◽  
Bond Stress ◽  
Reinforcing Bars ◽  
Bond Performance ◽  
Gfrp Bars ◽  
Pull Out ◽  
Reinforced Polymer ◽  
Glass Fiber Reinforced ◽  
Average Bond

Direct pull-out tests were performed to evaluate the bond performance of glass fiber-reinforced polymer (GFRP) reinforcing bars in cement mortar. Specimens with different bar diameters and different grouted lengths (i.e., 5d, 10d and 15d, d is the diameter of bars) are prepared for the pull-out tests. For comparison, specimens with plain aluminium alloy bars (AAB) were tested as well. The result shows that the average bond stress between plain aluminium alloy bars and cement is much smaller than that between the deformed GFRP bars and cement; thin GFRP bars tended to have larger average bond stress; the shorter the grouted length, the smaller the maximum average bond stress. Only part of grouted length undertakes the bond stress and the length depends on the shear modulus of GFRP and the surrounding material.

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