In this paper, fatigue crack propagation in adhesively bonded joints is analysed and discussed. An incident lamb wave interacts with a fatigue crack, and the second or third harmonics are generated. In this research, the mechanical and fracture behavior of adhesively bonded doublelap and steppedlap joints dljs and sljs composed of pultruded gfrp laminates and an epoxy adhesive were experimentally and numerically investigated under both quasistatic and fatigue loadings. The model employs a cohesive zone model described by a modified bilinear traction. To compare fatigue crack growth behavior with heatcured type adhesive, fatigue testing was also conducted for dcb joints with an epoxy adhesive. Fatigue crack propagation rate of cfrpaluminum adhesively. Modelling of adhesively bonded joints april 2001 twi. Three different bonded joints are considered in this. Fatigue tests were conducted on adhesivelybonded cfrpaluminum. A study on fatigue crack propagation in thick composite. The techniques are based on using fea combined with either fracture mechanics theory or the cohesive zone model.
Fatigue crack propagation behavior of adhesively bonded cfrpaluminum joints was investigated by ishii et al. Effect of humidity on the fatigue behaviour of adhesively. Fatigue and fracture of adhesivelybonded composite joints. Crack growth rate and crack path in adhesively bonded. Summary of work in which fatigue life and crack growth data were obtained for steel joints bonded with epoxy adhesive to compare with predicted values based on fracture mechanics concepts. May 01, 20 read a study on fatigue crack propagation in thick composite adhesively bonded joints, international journal of fatigue on deepdyve, the largest online rental service for scholarly research with thousands of academic publications available at your fingertips. Ashcroft b afaculty of engineering and physical sciences j5, university of surrey, guildford. Fatigue crack propagation behavior of adhesively bonded cfrpcfrp and cfrpaluminum joints flexural rigidity of the adherend 8,9. Mixedmode fatigue crack growth in fm37 bonded joints. An investigation on fatigue crack growth monitoring of bonded joints has been conducted employing a novel carbon nanotube adhesive film, chosen for their proven exceptional properties for sensing purposes. Three different bonded joints are considered in this study, namely double cantilever beams, single. In particular a cohesive damage model is implemented in the commercial software abaqus, in order to take into account for the damage produced by fatigue loading. Fatigue debond growth in adhesively bonded single lap joints 81 there have been many attempts to model the relation between the fatigue crack propagation rate, dadn, and the stress intensity range.
Recently, the framework for modelling adhesively bonded joints described above has been adapted in several studies to the modelling of fatigue initiation and propagation in bonded joints and in laminated composite. A procedure for the simulation of fatigue crack growth in. Components of the specimens were unidirectional composite, aluminum plate and a filmtype epoxy adhesive. The prediction of crack growth in bonded joints under. The use of structural adhesive joints to join carbon fibre reinforced polymer cfrp adherends is now well established in the aerospace industry. Fatigue debond growth in adhesively bonded single lap joints 81 there have been many attempts to model the relation between the fatigue crack propagation rate, d a d n. One of the major advantages of adhesive bonding, compared to riveting or welding, lies in its superior fatigue resistance. To acquire fatigue endurance and crack growth data from a galvanneal steel adherendepoxy adhesive system against which to compare fatigue life predictions based on fracture mechanics concepts. Fatigue crack propagation in adhesively bonded joints. Effect of humidity on the fatigue behaviour of adhesively bonded aluminium joints 175 latin american journal of solids and structures 14 2017 174187 in incredible structural efficiency and durability present in some aircrafts that could not have been achieved with conventional riveted structures hartsmith 2011. Fatigue damage of adhesively bonded joints, in addition to crashworthiness, has therefore become subject of unquestionable relevance. Fatigue crack growth simulation in adhesively bonded composite joints.
One of the main advantages of adhesive bonding is its high resistance. The paper is divided into several related topics such as fatigue strength and lifetime analysis, fatigue crack initiation, fatigue crack propagation, fatigue durability, variable fatigue. A current challenge is the shm of adhesively bonded composite joints, either 3layer systems of. Besides the sn curves, stiffness fluctuations were monitored during fatigue as well as crack initiation and propagation. Fatigue crack growth in adhesively bonded joints with intermittent. In this study, the fatigue crack growth rate was measured using adhesively bonded cfrp aluminum double cantilever beam dcb joints made with an acrylic adhesive.
The advantages of adhesively bonded joints over mechanically fastened joints has encouraged the aerospace industry to use the former in structural components and systems. Fatigue crack growth for bonded joints the fatigue crack propagation has been strongly investigated for bonded joints, and its life depends. This work deals with the simulation of the fatigue crack growth fcg in bonded joints. Fatigue crack growth identification in bonded joints by. Pdf the current paper presents research aiming at characterizing the fatigue behaviour of adhesively bonded joints. Fatigue is widely recognised as one of the most common causes of mechanical failure and hence the issue of fatigue in bonded joints must be addressed if adhesives are to find wider usage in structural applications.
Due to the increasing interest in adhesively bonded joints, mainly in the transports industry, there is a need to deep the knowledge about the fatigue behaviour of adhesive joints. Single lap shear fatigue tests have been carried out at a 7 kn load, load ratio 0. Jan 01, 2003 read the prediction of crack growth in bonded joints under cyclic fatigue loading i. Adhesively bonded joints are gaining importance in the structural joining processes competing against welding and bolting processes. Predicting the servicelife of adhesivelybonded joints. Fatigue crack propagation rate of cfrp aluminum adhesively bonded dcb joints with acrylic and epoxy adhesives 1. Fatigue crack growth in adhesively bonded compositemetal double. Adhesively bonded joints are often employed to join parts in composite structures. Citeseerx document details isaac councill, lee giles, pradeep teregowda. Fatigue failure of a doublelap joint involves two stages. The main aim of this article is to investigate the effect of frequency on fatigue crack propagation in adhesively bonded joints.
Simulating mode i fatigue crack propagation in adhesively. Dcb is a standard test specimen used to characterize mode i. The fatigue crack propagation in adhesively bonded, thick composite joints was investigated experimentally using double cantilever beam and single lap joint specimens. The experimental results and numerical analyses combined with the phenomenological models were used to establish mixedmode static and fatigue failure criteria for crack initiation and crack propagation for the adhesively bonded joints. The tensile fatigue response of adhesively bonded doublelap and steppedlap joints dljs and sljs has been investigated. Modelling fatigue in adhesively bonded joints springerlink. Damage mechanics iii fatigue crack propagation in adhesively. A common fatigue crack propagation curve for adhesively bonded joints is a logarithmic plot of crack growth rate against the maximum strain energy release rate over time figure. Including all of the detail of adhesively bonded joints into a model of a component will complicate an analysis because of several factors.
Lamb wavebased structural health monitoring of delamination. Fatigue life and backface strain predictions in adhesively. However, the lack of knowledge regarding fatigue and fracture behaviour, and the shortage of tools for credible fatigue design, hinders the potential benefits of adhesively bonded joints. In situ health monitoring of adhesively bonded joints during. In situ health monitoring of adhesively bonded joints during fatigue using carbon nanotube network roham mactabi a thesis in the department of mechanical and industrial engineering presented in partial fulfillment of the requirements for the degree of master of applied science mechanical engineering at concordia university. Fatigue debond growth in adhesively bonded single lap joints.
It has many applications in aerospace, automotive and other industries. In the frame of this work fatigue behavior of adhesively bonded joints composed of pultruded gfrp laminates is thoroughly investigated. In 3d solid models, thin bondlines will require large numbers of elements model the adhesive. Fatigue crack propagation behavior of adhesivelybonded. Tapered single lap joints made of relatively thick composite laminate adherends.
Fatigue crack propagation behavior of adhesively bonded. The paper presents a concept for predicting fatigue strength of adhesive bonded joints based upon stresses that the joint interface may experience under operating conditions. An innovative approach to characterize the resistance of adhesively bonded joints to fatigue disbond propagation fdp is presented. An innovative approach to fatigue disbond propagation in. Predicting fatigue damage in adhesively bonded joints using a. In this work a procedure based on the cohesive damage model is developed for the simulation of fatigue crack growth in bonded joints for different mixed mode iii conditions.
Crack growth in adhesively bonded joints subjected to. Mixedmode static and fatigue failure criteria for adhesively. Crack growth rate and crack path in adhesively bonded joints. The first part of the book discusses the experimental investigation of the reliability of adhesivelybonded composite joints, current research on understanding damage mechanisms, fatigue and fracture, durability and ageing as well as implications for design. The first part of the book discusses the experimental investigation of the reliability of adhesively bonded composite joints, current research on understanding damage mechanisms, fatigue and fracture, durability and ageing as well as implications for design. Fatigue crack growth simulation in adhesively bonded. Three different bonded joints are considered in this study, namely double cantilever beams, single lap joints and double lap joints.
Such joints produce lower stress concentration than the mechanically fastened joints and have high strength to weight ratio. In the present situation, the effect of adherend thickness on fatigue or fracture toughness has been still unclear. Fatigue tests were conducted on adhesively bonded cfrpaluminum doublecantilever beam dcb specimens to investigate the effect of adherend thickness on the fatigue crack growth rate. Dec 04, 2017 the fatigue damage process in the dljs was dominated by a fatigue crack initiation process. Dljs showed low and almost linear stiffness degradation during fatigue life. Abdel wahab mm, ashcroft ia, crocombe ad and smith pa 2003 fatigue crack propagation in adhesively bonded joints. Fatigue crack growth identification in bonded joints by using. Fatigue delamination growth for an adhesivelybonded. A study on fatigue crack propagation in thick composite adhesively bonded joints 1. The above trend is similar to that for the present fatigue tests.
The primary inputs to predict crack growth rates are fracture mechanics based test data and finite element data of bonded joints. To do so, series of fatigue crack growth tests for two different amounts of tightening torque in aluminum alloy 2024t3 precracked joints have been carried out to record the fatigue crack. Two types of joints are examined, double lap joints dlj and stepped lap joints slp to point out the influence of different joint geometries in fatigue life. Fatigue failure of adhesivelybonded structural joints for. This paper addresses numerical and experimental examination of the role of zigzag interface shapes on the load bearing capacity and fatigue life of adhesively bonded single lap joints. Read a study on fatigue crack propagation in thick composite adhesively bonded joints, international journal of fatigue on deepdyve, the largest online rental service for scholarly research with thousands of academic publications available at your fingertips. In this study, the fatigue crack growth rate was measured using adhesively bonded cfrpaluminum double cantilever beam dcb joints made with an acrylic adhesive. The joints have features that are much smaller than the dimensions of the structure. Fatigue behaviour of adhesively bonded joints and its. Three different bonded joints are considered in this study, namely double cantilever beams, single lap joints and double lap. Adhesively bonded doublecantilever beam dcb samples were tested in fatigue at various frequencies between 0. The study of changes in the fatigue response on adhesively bonded joints due to varying degrees of relative humidity is an important step in understanding how joints will behave in the longterm, and although there is already some data on the subject it is not enough to draw clear conclusions costa et al. Fatigue crack propagation rate of cfrpaluminum adhesively bonded dcb joints with acrylic and epoxy adhesives 1.
Fracture and fatigue of adhesivelybonded fiberreinforced. The crack measurement techniques and the calculation methods for. Read the prediction of crack growth in bonded joints under cyclic fatigue loading i. License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Cohesive zone model for highcycle fatigue of adhesively. Fatigue of adhesively bonded epoxyaa6061t651 joints.
Ashcroft b afaculty of engineering and physical sciences j5, university of surrey, guildford, surrey gu2 7xh, uk. However, longterm behaviour of adhesively bonded joints is still an open question. The second harmonics generation of the fundamental s0 mode is much more sensitive to the fatigue cracks than a0 mode 6. Adhesive bonding has become a powerful joining technique during the last few decades. Fatigue delamination growth for an adhesively bonded composite joint under mode i loading. The crack growth was modelled using a fracture mechanics model based on finite element models. The fatigue response of environmentally degraded adhesively. A numerical model has been developed for simulating fatigue crack growth debonding in adhesively bonded composite joints subjected to mode. Abstract a numerical model has been developed for simulating fatigue crack growth debonding in adhesively bonded composite joints.
Ashcroft b a faculty of engineering and physical sciences j5, university of surrey, guildford. The demand for reliable and safe structures necessitates deep knowledge in this area in order to avoid catastrophic structural failures. Jhin master of applied science mechanical and industrial engineering university of toronto 2012 abstract the relationship between crack path and test method was examined by comparing the. The fatigue behaviour of adhesivelybonded joints, which consisted of an epoxyfilm adhesive bonding fibrecomposite substrates, has been studied. This paper presents a method for predicting fatigue crack propagation in single lap adhesively bonded composite joints with an initial fullwidth preexisting disbond using finite element analysis and numerical integration of the fatigue crack growth rate law. For both joint types, the dominant failure mode was a fibertearoff failure that occurred in the outer mat layers of the gfrp laminates. The backface strain technique was employed to monitor damage initiation and propagation in the joints. A fracture mechanics approach to adhesively bonded joints. Home key engineering materials advances in fracture and damage mechanics iii fatigue crack propagation in adhesively bonded. Accurate prediction of fatigue life is a challenge due to the complicated nature of fatigue crack initiation and propagation, geometry of bonded joints, and. Experimental studies, international journal of adhesion and adhesives on deepdyve, the largest online rental service for scholarly research with thousands of academic publications available at your fingertips. A fracture mechanics approach to adhesively bonded joints twi. A study on fatigue crack propagation in thick composite adhesively bonded joints article in international journal of fatigue 50.
Predicting fatigue damage in adhesively bonded joints. Simulating mode i fatigue crack propagation in adhesivelybonded. Experimental samples were made from carbon fibre composite substrates bonded with an epoxy adhesive. Effect of interface nonflatness on the fatigue behavior of.
A finite element study of fatigue crack propagation in. Development of a monitoring system for crack growth in. The mechanics of the possible modes of fatigue damage propagation in these joints when subjected to constant amplitude cyclic mechanical loading were investigated. Pultruded gfrp laminates were joined using an epoxy adhesive.
To correlate the structural performance of the joints. Adhesively bonded joint, composite, fatigue crack propagation. The joints were aged in deionised water at a temperature of 50. A finite element study of fatigue crack propagation in single. The first part of the book discusses the experimental investigation of the reliability of adhesively bonded composite joints, current research on understanding damage mechanisms, fatigue and fracture, durability and ageing as well as. Dcb is a standard test specimen used to characterize mode i fracture in adhesivelybonded joints. A constitutive equation, known as the modified crack layer mcl model, is employed to extract parameters characteristic of the adhesive joints resistance to fdp. In the case of a joint experiencing only peel stresses, a fracture mechanics fm approach simply requires the evaluation of mode i crack driving force as a function of crack length in the joint and the knowledge of the mode i fatigue crack growth fcg behaviour 2. Fatigue tests were conducted on adhesivelybonded cfrpaluminum doublecantilever beam dcb specimens to investigate the effect of adherend thickness on the fatigue crack growth rate. The fatigue crack propagation has been strongly investigated for bonded joints, and its life depends on the extension of the bonded interface, the load type and the load level 14, 15. Fatigue crack propagation behavior of adhesivelybonded cfrpaluminum joints.
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