Vast
number of studies dedicated to
study
the structural failure, design parameters, and failure modes of externally bonded FRP. The performance of this system is dominated by the bond behavior between FRP and concrete. This bond behavior can be greatly influenced by the environmental factors that can lead
premature failure. Understanding the long-term behavior and degradation of this system under various environmental factors is as important as the short-term performance. Despite
the extensive literature dedicated for studying the durability of the FRP system, most of these studies focused on the effect of an isolated degrading agent such solar radiation (UV), freeze and thaw, moisture and temperature. Thus, less attention was given to the combined effect of two or more agents, which represents the real case situation. The hygrothermal environment including the combined effect of moisture and temperature is considered the most aggressive environment for FRP [7] [8] [13]. On one hand, moisture can plasticize and degrade the epoxy bonding between FRP and concrete through the hydrolytic breakdown between matrix and FRP. Moreover, it can reduce the Tg. On the other hand, temperature close or higher than the Tg can significantly reduce the bond strength [14][3][4]. Temperature coupled with moisture can accelerate the degradation by increasing the rate of moisture absorption.
In this research, the behavior of FRP sheets bonded with epoxy resin in wet layup technique is going to be investigated. There are two reasons for investigating this system (1) this system is widely used in the rehibition and strengthening of the masonry wall and infrastructure that is commonly exposed to
hygrothermal
environment; (2) since It has a lower Tg, it is expected to be more
effected
by hygrothermal environment especially in a temperature close to the service temperature.
The experimental program will explore the degradation of the bond after exposure
into
two hygrothermal conditions which are (1) moisture combined with different ranges of temperature; (2) water immersion combined with
various
range
of temperature. Single-lap shear and
pull-off
test
will be used to investigate bond degradation as shown in the Figure. The effect of the
conditions on the modules of elasticity of the FRP and Tg will be also evaluated and measured. Finally, an analytical model is going to be proposed to determine the degradation of the bond strength.
Figure 1: a) single-lap shear test; b) pull-off test
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