Cover page describe the Typical fracture surface of nuclear graphite blocks after irradiation (cracks occur during reactor operation). This picture Summarize the Fractographic studies of GR-280 nuclear graphite after irradiation up to neutron fluence above the turnaround dose (with a decrease in of the mechanical properties to the values close to the initial one after primary radiation-induced increase) showed along with the presence of transcrystalline fracture, appearance of intercrystalline fracture regions along the “filler-binder” type boundaries.
Behavior of EB FRP masonry bond under service temperature
Zuhair Al-Jaberi1, John J. Myers2*, K. Chandrashekhara3
1Graduate Research Student: Civil, Arch. and Envir. Engr, Missouri University of Science and Technology, Rolla, MO 65409, USA
2Professor of Civil, Arch. and Envir. Engineering and Associate Dean, Missouri University of Science and Technology, Rolla, MO 65409, USA
3Curators Distinguished Professor of Mechanical Engineering, Missouri University of Science and Technology, Rolla, MO 65409, USA
Adv. Mater. Lett., 2018, 9 (11), pp 753-759
Publication Date (Web): Jul 24, 2018
Copyright © 2018 VBRI Press
The interest in advanced composites in repairing and strengthening infrastructure systems has considerably increased, especially as the application externally bonded (EB) fiber reinforced polymer (FRP) has become more well established. Previous research on bond behavior has focused on impact of durability by considering exposure to harsh environmental conditions and testing the specimens after exposure, rather than testing bond performance during exposure. The influence of directly applying temperature on bond behavior represents an open topic that needs to be investigated in more detail. This study is one of the first studies to investigate the bond behavior when the composite is subjected to tension force simultaneously with applying temperature. The temperatures considered in this study were at freezing, ambient, and high temperature, which are more representative of structural elements under field conditions. A total of 16 specimens were strengthened and tested under single-lap direct shear. The key parameters investigated include (a) the type of fiber [laminate carbon vs. wet layup glass] (b) the level of temperature applied on specimen, including ambient condition 21°C (70 °F), freeze condition -18 °C (0 °F) and hot weather 49 °C (120 °F), and (c) the exposure regime (direct exposure during loading process vs. loading after exposure). Most of the specimens were subjected to tension force simultaneously with applying temperature, and the other specimens were later tested after exposure to the heating and cooling cycles. These cycles are proposed to simulate 20 years of the typical in-situ weather conditions in the Central United States. The results showed that overall the EB strengthening systems exhibited good performance when subjected to cycles of heating and cooling prior to testing. High reduction of FRP-epoxy bond properties was up to 59% when exposed to high service temperatures. Different modes of failure were observed such as debonding at fiber-matrix interface and debonding due to shearing in laminate.
Masonry, bond, FRP, temperature, durability.