Stress Analysis Of Adhesively Bonded Joints On Single Lap Joints

Abstract

The demand for adhesive applications in bonded joints has increased considerably over recent years. This growth is due to the benefits provided by adhesives, when compared to conventional joining methods, like rivets, bolts or welding. Therefore, there is a specific need for analysis can provide physical insight and accurate results for bonded joints applications.

Several analytical methods for the calculation of stress distributions in adhesively bonded joints have been discussed previously. In this paper was done a revision of the main analytical and finite element method (FEM) was performed.

TABLE OF CONTENTS

COVER PAGE

TITLE PAGE

APPROVAL PAGE

DEDICATION

ACKNOWLEDGEMENT

ABSTRACT

CHAPTER ONE

• INTRODUCTION
• BACKGROUND OF THE STUDY
• STATEMENT OF THE PROBLEM
• AIM AND OBJECTIVES OF THE STUDY
• SCOPE OF THE STUDY
• SIGNIFICANCE OF THE STUDY

CHAPTER TWO

LITERATURE REVIEW

• REVIEW OF THE STUDY
• COMMON STRESS TYPES IN ADHESIVE JOINTS
• STRESSANALYSIS
• BONDEDJOINTAPPLICATIONSININDUSTRY
• REVIEW OF RELATED STUDIES

CHAPTER THREE

RESEARCH METHODS

• INTRODUCTION
• THEORETICALANALYSIS
• FINITEELEMENTANALYSIS

CHAPTER FOUR

4.0      RESULTS AND DISCUSSION

CHAPTER FIVE

• CONCLUSION
• RECOMMENDATION

CHAPTER ONE

1.0                                INTRODUCTION

1.1                  BACKGROUND OF THE STUDY

Thesingle-lapjointisoneofthe mostcommon‘plate-to-plate’jointdesignsemployedinindustry.They areeasy andcheap to manufacture because there are no splice details to make or locate in the bondingfixture. The single-lap joint is easy to inspectultrasonically,becauseacompleteinspectioncan be made from one side of the joint. In addition, the single-lap joint under tension poses aproblem which is oftenusedtodemonstratetheaccuracy oftheoriesforcalculating thestresses in adhesivelybonded joints.

The application of adhesives in bonded joints has been greatly increased over recent years. This growth is due to the benefits provided by adhesives, when compared to conventional joining methods, such as: more efficient load transfer, possibility to conform light weight structures, enhanced fatigue properties, improved corrosion resistance, smoother surfaces, among others. The analytical methods for the calculation of stress distributions in adhesively bonded joints are carried out in this work.

1.2      STATEMENT OF THE PROBLEM

Despite the considerable efforts of anumber ofresearchersoverthelasthalf-century,controversy andunresolvedissuesstillremain. Mainly that the failure load of a joint is still very hard to predict and that theoriesincorrectlyshowthe strengthof a jointto increase withincreasingadhesive thickness.theoritical and finiteelementanalysis of a bonded joints on single lap joints was carried out in this study.

1.3     AIM AND OBJECTIVES OF THE STUDY

The main aim of this work is to determine the stress analysis of adhesively bonded joints on single lap joints.

The objectives of the study are:

1. To study an overview of a bonded joints on single lap joints
2. To carryout a theoritical and finiteelementanalysis of a bonded joints on single lap joints

• To study the applications of a bonded joints on single lap joints

1.4     SIGNIFICANCE OF THE STUDY

This paper was significantly important indrawing attention to the effects ofadherend bending deflectionsonthenormalandshear stresses in the adhesive layer of a single lap joint. This study shall serve as a means of expanding theknowledgeonanalysismethodsforstructuralbondedjoints

1.5     SCOPE OF THE STUDY

In the analysis stage of the design cycle important properties to consider are the strength,stiffness, weight and cost of the bonded assembly. In this overview the analysis of bondedjointswillbelimitedtothepropertieseffectingthejointstrengthbystaticloading.

CHAPTER FIVE

5.1                                CONCLUSIONS

By using a linear FE analysis the peak shear and peel stresses are shown to increase withincreasingbondlinethickness.Averageadhesivestressesareshowntodecreasewithincreasing bondline thickness.Further the results have shown thatanoptimumbondlinethickness exists, just as the experiments have shown. It appears that for purposes of a jointdesign using average stresses over the bondline thickness (or assuming constant stresses overthe bondline) can lead to some major misinterpretations regarding the joint behaviour even ifonly thin bondlines are analysed (0.05 mm – 0.5 mm). The popular belief or hypotheses thatthe increasedporosity andmicro-cracksisthe sole cause ofthe lower failuresforthickbondlinesisnotsubstantiatedbythecurrentanalysis.However,itispossible,ifnotexcludedin the theoreticalassumptions, thatporosityandmicro-cracks couldbeacontributing factor.

Thisworkclearlydemonstratestheimportanceofusinginterfacestressesinfailurecriteriaor general analysis of bonded joints. Whether bonded joints are manufactured well or poorlythistheoryexplainsthedecreaseinjointstrengthcommonlyobservedwiththickerbondlines.

5.2                                    SUMMARY

Clearly most of the design rules and assumptions of theoretical models for adhesive joints aredrawnfromthesingle-lapjointanalysesthathavereceivedsomuchattentionoverthelasthalf century. However, a satisfactory model has still yet to be developed, and its mechanicalunderstanding is still very important considering its wide spread use throughout industries.Alsofortheanalysisofotherjointconfigurationsitprovidesaveryusefulstartingmodel.The followingpoints from this overview canbe drawn:

• Thevariousfeaturesomittedinanalyticalanalysestoenableclosed-formsolutionstobeobtained have little effect on thefinalaccuracyof the solution.
• Themaindisadvantage ishowtotreatthe stresssingularityatthe bi-materialinterfaces.
• Itremainsasubjectoffurtherresearchtodetermineahypothesistoexplainwhytheories(including FEs) are unabletopredict theeffect of bondlinethickness on joint strength.