Near free-edge stresses in FRP-to-concrete bonded joint due to mechanical and thermal loads

Abstract

19Over the last few decades, a considerable amount of theoretical and experimental investigations have been 20 conducted on the mechanical strength of composite bonded joints. Nevertheless, many issues regarding the 21 debonding behavior of such joints still remain uncertain. The high near free-edge stress fields in most of these 22 joints are the cause of their debonding failure. In this study, the performance of an externally bonded fiber-23 reinforced polymer (FRP) fibrous composite to a concrete substrate prism joint subjected to mechanical and 24 thermomechanical loadings is evaluated through employing the principles of lamination theory. An inclusive 25 Matlab code is generated to perform the computations. The bond strength is estimated to take place in a region-26 2 also termed the boundary layer-where the peak interfacial shearing and transverse peeling stresses occur; whereas 27 the preceding stress field is observed to be the main failure mode of the joint. The proposed features are validated 28 through the existing experimental data points as well as the commercial finite element (FE) modeling software, 29Abaqus. Comparison between the calculated and experimental results demonstrates favorable accord, producing 30 quite a high average ratio. The current approach is advantageous to failure modeling analysis, optimal design of 31 bonded joints, and scaling analyses among others. 32Keywords: FRP-to-concrete bonded joint; thermomechanical load; free-edge interfacial stress; boundary 33 layer; debonding failure; finite element method 34 35 3 1. Introduction 36Bonded joints are significantly desired in comparison to mechanical bolts, rivets, and welds due to 37 their compact design, low manufacturing cost, enhanced mechanical durability, sound noise 38 suppression, and obvious reduction of weight. Accordingly, they have been extensively adopted and 39 increasingly used in order to transfer load in structural elements and connections in civil structures 40 [1]. Furthermore, the problem of function degradation in such structures has gained exceptional 41 concern over the past several years [2, 3]. Meanwhile, thermal stresses play a very important role in 42 the study of bonded joints for a variety of reasons. On the one hand, these joints have considerable 43 residual thermal stresses from the fabrication process. On the other hand, the materials are to be 44 selected in order to behave well at elevated or dropped temperatures. The adherends shall thus retain 45 their properties at such temperatures; this is particularly true about the composite materials. They can 46 be chosen in that the coefficient of thermal expansion (CTE) is a specified value, possibly zero [4]. 47As a historical point of view, Timoshenko conceived the concept of free-edge stress, who first 48 considered the deflection of bimetal thermostats subjected to uniform change of temperature [5]. 49 Later, continuous shear springs were practiced in bonded joints, in order to find the maximum 50 singular stresses at the edges [6]. This j...

Probabilistic reliability analysis for active vibration control of piezoelectric laminated composite plates using mesh-free finite volume method

“…At the present time, the commonly implemented piezoelectrics used in engineering are mostly ceramics and composites (Mokhtari et al, 2021). In the interim, the distinct characteristics of composites such as higher strength, thermal resistance, electric conductivity, fatigue life, and lightness have provided scholars to improve different methods to include piezoelectrics in a growing range of engineering systems (Samadvand and Dehestani, 2020a, 2020b). However, these systems are almost always imperfect.…”