scholarly journals Hygrothermal Aging of Amine Epoxy: Reversible Static and Fatigue Properties

2018 ◽  
Vol 8 (1) ◽  
pp. 447-454 ◽  
Author(s):  
Andrey E. Krauklis ◽  
Abedin I. Gagani ◽  
Andreas T. Echtermeyer
Keyword(s):  
Fiber Reinforced Polymers ◽  
Fatigue Properties ◽  
Initial Water Content ◽  
Initial Water ◽  
Reinforced Polymers ◽  
Structural Applications ◽  
High Concern ◽  
Static Tensile ◽  
Aging Mechanisms

Abstract Fiber-reinforced polymers (FRP) are widely used in structural applications. Long-term properties of such materials exposed to water are of high concern and interest, especially for subsea and offshore applications. The objective of this study is to identify the mechanisms and to identify whether drop in properties of diamine-cured mixed DGEBA-HDDGE is reversible upon drying the material to its initial water content. The properties of interest are mechanical strength, elastic properties and fatigue performance, as well as changes in chemical structure. The effect of absorbed water on the properties of the resin is evaluated, and hygrothermal effects and aging mechanisms are discussed. Furthermore, it is shown experimentally that the tension fatigue S-N curve of a wet epoxy resin can be estimated by shifting the S-N curve of a dry material proportionally to a reduction in static tensile strength due to hygrothermal effects.

scholarly journals Bond-Slip Models for FPR-Concrete Interfaces Subjected to Moisture Conditions

2017 ◽  
Vol 2017 ◽  
pp. 1-14 ◽  
Author(s):  
Justin Shrestha ◽  
Dawei Zhang ◽  
Tamon Ueda
Keyword(s):  
Fiber Reinforced Polymers ◽  
Experimental Investigations ◽  
Reinforced Polymers ◽  
Bond Slip ◽  
Exposure Effect ◽  
Pull Out ◽  
Proposed Model ◽  
Maximum Period ◽  
Moisture Conditions

Environmental related durability issues have been of great concerns in the structures strengthened with the fiber reinforced polymers (FRPs). In marine environment, moisture is one of the dominant factors that adversely affect the material properties and the bond interfaces. Several short-term and long-term laboratory experimental investigations have been conducted to study such behaviors but, still, there are insufficient constitutive bond models which could incorporate moisture exposure conditions. This paper proposed a very simple approach in determining the nonlinear bond-slip models for the FRP-concrete interface considering the effect of moisture conditions. The proposed models are based on the strain results of the experimental investigation conducted by the authors using 6 different commercial FRP systems exposed to the moisture conditions for the maximum period of 18 months. The exposure effect in the moisture conditions seems to have great dependency on the FRP system. Based on the contrasting differences in the results under moisture conditions, separate bond-slip models have been proposed for the wet-layup FRP and prefabricated FRP systems. As for the verification of the proposed model under moisture conditions, predicted pull-out load was compared with the experimental pull-out load. The results showed good agreement for all the FRP systems under investigation.

A new approach of stiffness degradation modeling for carbon fiber-reinforced polymers under cyclic fully reversed bending

2017 ◽  
Vol 51 (20) ◽  
pp. 2889-2897 ◽  
Author(s):  
Ali Amiri ◽  
Matthew N Cavalli ◽  
Chad A Ulven
Keyword(s):  
Fatigue Life ◽  
Carbon Fiber ◽  
Fatigue Behavior ◽  
Flexural Modulus ◽  
Fiber Reinforced Polymers ◽  
Fiber Reinforced ◽  
Carbon Fiber Reinforced Polymers ◽  
Reinforced Polymers ◽  
Structural Applications ◽  
Carbon Fiber Reinforced

Carbon fiber-reinforced polymers are being used in advanced structural applications such as aerospace, automotive, and naval industries. Therefore, there is a rising need for predicting their fatigue life and improving their fatigue behavior. In this study, the fatigue behavior and changes in flexural modulus of bidirectional carbon fiber-reinforced polymers due to cyclic fully reversed bending are investigated. A unique fixture is designed and manufactured to perform fully reversed four-point bending fatigue tests on (0 °/90 °)15 carbon/polyester specimens with a stress ratio of R = −1 and frequency of 5 Hz. The expected downward trend in fatigue life with increasing maximum applied stress was observed in the S–N curves of samples. Based on the decay in the flexural modulus of the specimens, a modified exponential model is proposed to predict the life of carbon fiber-reinforced polymers under fully reversed bending. The empirical constants in the model are calculated based on the results of experiments. The model is applied to predict the fatigue life of the samples that did not fail during the tests and cycle-to-failure of the specimens are found.

Test Research on the Long-Term Consolidation Mechanism of Ultra-Soft Clay

2013 ◽  
Vol 671-674 ◽  
pp. 146-150
Author(s):  
Ai Min Liu ◽  
Shu Wang Yan ◽  
Jing Shuang Li
Keyword(s):  
Construction Projects ◽  
Land Reclamation ◽  
Soft Clay ◽  
Initial Water Content ◽  
Strength Increase ◽  
Vacuum Preloading ◽  
Initial Water ◽  
Design Requirements ◽  
Test Result

Although the settlement of ultra-soft clay improved by the vacuum preloading technique was large in land reclamation projects, usually exceeding the theoretical calculation value by a large amount, the strength increase was relatively small. As a result the foundation would not meet the design requirements for strength. So a test was conducted to investigate the effect and mechanism of long-term consolidation of ultra-soft clay in laboratory in a period of over 691 days. A preloading load of 80kPa was used in this drainage consolidation test. The test result showed that for the ultra-soft clay with a high initial water content but a small strength, the settlement is large with a large strength increase, but the shear strength was relatively low. These results should draw much attention in application of vacuum preloading technique in construction projects.

scholarly journals PENGARUH KADAR AIR AWAL KAYU JATI DAN SUHU CURING PEREKAT PADA KEKUATAN GESER SAMBUNGAN KAYU JATI (TECTONA GRANDIS) SECARA PEREKATAN

2014 ◽  
Vol 4 (2) ◽  
Author(s):  
Sugiman Sugiman ◽  
Abdul Hayyi Nu’man ◽  
Emmy Dyah Sulistyowati
Keyword(s):  
Shear Strength ◽  
Water Content ◽  
Tectona Grandis ◽  
Curing Temperature ◽  
Initial Water Content ◽  
Fick’S Law ◽  
Initial Water ◽  
Fick's Law ◽  
Structural Applications ◽  
Teak Wood

Adhesively wood-wood bonded joint has been widely used in structural applications, however because wood is a hygroscopic material that absorbed water from environment, hence the absorbed water affects the joints performance. The objective of the paper is to investigate water absorbtion and desorbtion behaviour and the combined effect of absorbed water into the wood before being bonded and adhesive curing temperature on the shear strength of teak wood joints. The initial water content in the wood was 0%, 37%, and 54%, while the curing temperature was a  room temperature for 24 hours, 50°C for 6 hours, and 100°C for 3 hours. The water absorbtion behaviour of teak wood deviate from the Fick's law, however the desorbtion tends to follow the Fick's law. Moreover the rate of absorbtion is higher than the rate of desorbtion. At the same curing temperature, the increase of water content decreases the shear strength of the joints; however the decrease was compensated by increasing the curing temperature. Curing at a high temperature (100 oC) improves the joints strength in all moisture content studied and the failure of the joints occurs at the wood.

Experimental Research on Coupling of Swelling Rock between Swelling and Creep

2013 ◽  
Vol 353-356 ◽  
pp. 293-302
Author(s):  
Qiu Yan Fan ◽  
Mei Qian Wang ◽  
Xian Li ◽  
Bo Zhang
Keyword(s):  
Creep Deformation ◽  
Residual Deformation ◽  
Swelling Pressure ◽  
Initial Water Content ◽  
Term Strength ◽  
Compression Tests ◽  
Initial Water ◽  
Multi Stage ◽  
Swelling Rock

Swelling rock has the properties of swelling and creep. Researches on coupling between swelling and creep have not yet been carried out. The expansive Paleogene mudstone is used to laboratory uniaxial compression tests, to find the coupling regularity between swelling and creep under different initial water contents, influent modes and loading methods. For coupling, the creep curves show similar characteristic of non-coupling. The creep deformation increases obviously and the long-term strength decreases comparing with non-coupling. With increasing initial water content, the creep deformation increases for coupling. The creep deformation increases with the enlargement of water-absorption area during the coupling creep. For single-stage and multi-stage loading, the creep regularity is similar to non-coupling. The sample will have a permanent residual deformation when unloaded at the second stable creep stage. The long-term strength of swelling rock is greater than the swelling pressure and the long-term strength is lower than that of non-coupling.

Permeation Tests on Tianluoshan Relic Soils with Methyl Acrylic Acid Resin

2013 ◽  
Vol 726-731 ◽  
pp. 3706-3709 ◽  
Author(s):  
Pei Hang Chen ◽  
Xin Jun Chai ◽  
Jin He Gao ◽  
Yu Jiao Wang
Keyword(s):  
Acrylic Acid ◽  
Water Content ◽  
Influence Factors ◽  
Degree Of Saturation ◽  
Dry Density ◽  
Initial Water Content ◽  
Initial Water ◽  
Acid Resin ◽  
Long Term Preservation

Tianluoshan relic sites is a typical earthen sites located at moisture circumstances, where craking, chalking, flaking and mould are the main geological diseases after excavation. For public exhibition and long-term preservation purpose, chemical stabilization were required. In this study, the potential application of methyl acrylic acid resin for solidification of Tianluoshan relic soils were evaluated by a series of laboratory permeation tests. The main considered influence factors include: dry density, initial water content and degree of saturation. The results show that the permeation effect of methyl acrylic acid resin were greatly related with dry density and initial water content of the earthen soils, the practical application guidance are also presented.

scholarly journals Durability of FRP Reinforcements and Long-Term Properties

2020 ◽  
Vol 28 (2) ◽  
pp. 50-55 ◽  
Author(s):  
Katarína Gajdošová ◽  
Róbert Sonnenschein ◽  
Stanislav Blaho ◽  
Simona Kinčeková ◽  
Ján Pecka
Keyword(s):  
Experimental Studies ◽  
Fiber Reinforced Polymers ◽  
Actual Behavior ◽  
Design Codes ◽  
Reinforced Polymers ◽  
Frp Composites ◽  
Impact Reduction ◽  
Long Term Behavior ◽  
Insufficient Knowledge

AbstractAlthough fiber-reinforced polymers (FRPs) have achieved increasing popularity in strengthening concrete structures and reinforcing new ones, there is to date insufficient knowledge about their long-term behavior. The long-term properties of FRPs specified in design codes lead to the low utilization capacity of these materials and are not supposed to be correct according to the actual behavior of structures reinforced with FRPs after 20 or 30 years of their use. Environmental impact reduction factors limit the mechanical properties of FRP composites in a range from 0.95 for CFRP to 0.5 for GFRP; the creep rupture factor is from 0.9 to 0.2. The paper summarizes previous research and experimental studies on the long-term properties of FRP reinforcements and also their comparison with the actual structures in which this reinforcement has been used; it presents the first part of an experimental investigation with comparative calculations.

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