Analysis of single lap adhesive joint

1. Major Project Synopsis Presentation
DAYANANDA SAGAR COLLEGE OF ENGINEERING
Shavige Malleshwara Hills, Kumaraswamy Layout, Bangalore-560078
(An Autonomous Institute affiliated to VTU, Approved by AICTE &ISO 9001: 2008 Certified)
Accredited by National Assessment & Accreditation Council (NAAC) with ‘A’ Grade
Department of Mechanical Engineering
Title: Experimental and failure analysis of CFRP-CFRP (Carbon fiber reinforced plastic) single lap
adhesive joint
Guide Name NITHESH BHASKAR N
Designation ASSISTANT PROFESSOR
Student Name 1. THANOJ KUMAR K 2. SUHAS R 3. YASHWANTH V H 4. SRIKANTH N
USN 1DS19ME150 1DS19ME143 1DS19ME159 1DS19ME140
Batch
Number
40

2. Introduction:
 The adhesive bonding process is widely used in the aerospace industry because
of sealing, insulation and good mechanical properties. The demand for adhesive
applications in structural 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 and design that can provide physical insight and
accurate results for bonded joints applications and further reducing weight.
 The single-lap joint is the basic connection form of bonded structure. The failure
analysis of composite-to-composite material single lap joints can help us
understand better the behavior of such material joints.
 Using of riveted joints in aircrafts may cause problems like stress concentration
near the holes and corrosion resulting in damage. To overcome this we need to
find an alternative, in this case we are testing adhesive joints.

3. Abstract:
Here the stress distribution analysis and tensile strength assessment of
CFRP bonded joint is studied by using Araldite AW106 adhesive. First
the CFRP-CFRP single lap joint is made. Since failure is initiated at the
ends of overlap, the stress distribution at the ends of the overlap and
bonded joint was analyzed using Ansys software. After the stress
distributions were analyzed based on the result obtained the
experimental steps were followed to assess the tensile strength of
bonded joint. The stress distribution analysis and the tensile strength
assessment results showed an agreement that the geometrical factors
directly affect the reliability of the bond.

4. Literature survey:
 Henok Yilma Kebede et.al carried out their work in “Tensile Strength Assessments of CFRP
Adhesive Bonded Joint”
In this paper, stress distribution analysis and tensile strength assessment of CFRP bonded joint were
studied. First a mixture of Epoxy adhesives and MWCNT was fabricated. Since failure is initiated at the ends of
overlap, the stress distribution at the ends of the overlap and bonded joint was numerically analyzed. After the
stress distributions were analyzed based on the result obtained the experimental steps were followed to assess
the tensile strength of bonded joint. The stress distribution analysis and the tensile strength assessment results
showed an agreement that the geometrical factors directly affect the reliability of the bond.
 Przemysław dobrzański et.al carried out their work in “design and analysis methods for
composite bonded joints ”
In this paper an experiment on existing design and analysis methods for composite adhesively
bonded joints has been conducted. Methods that might form a basis for development of practical engineering
methodology for adhesively bonded joints were selected and described. Starting from the simplest and the
fastest analytical methods (closed-form solutions): average shear stress, shear lag model and adhesive beam
model through more complex and more time consuming numerical methods supported by finite element
analysis: global models, local models, cohesive zone models. Assumptions and applicability of each method
was discussed.

5.  Ankit R. Sharma et.al carried out their work in “Variation of Adhesive Strength in Single Lap
Joint (SLJ) with Surface Irregularities”
Single Lap Joints are used extensively in the aerospace industry due to their lower weight and absence of
stress concentration due to drilling of holes. However, their lesser strength remains an important limitation.
Different modes of failures have been reviewed here. The bond strength of a Single Lap Joint can be varied by
varying its overlap length, however, the strength does not strictly increase with increasing bonding length.
Rather, it increases up to an optimum value and decreases further. This optimum value has been obtained, and
is found to be in agreement with previous studies in this regard.
 Farhad Asgari Mehrabadi carried out his work in “Experimental and Numerical Failure Analysis
of Adhesive Composite Joints”
In this paper ,three types of adhesive hybrid lap-joints, that is, Aluminum-GFRP (Glass Fiber
Reinforced Plastic), GFRP-GFRP, and Steel-GFRP were employed in the determination of adhesive hybrid joints
strengths and failures that occur at these assemblies under tension loading. . In the case of hybrid lap-joint
tests, a numerical modeling was also performed to determine the adhesive stress distribution and stress
concentrations in the side of lap-joint. Results are discussed in terms of their relationship with adhesively
bonded joints and thus can be used to develop appropriate approaches aimed at using adhesive bonding and
extending the lives of adhesively bonded repairs for aerospace structures.

6. • Jochen Schanz et.al conducted “Comprehensive study on the influence of different
pretreatment methods and structural adhesives on the shear strength of hybrid
CFRP/aluminum joints”
The aim of this study was to investigate the influence of laser treatments with varying
energy density and wavelength on the surface structure, shear strength and fracture behavior of
hybrid compounds of thermoset carbon fiber-reinforced polymer (CFRP) and aluminum (Al) bonded
with three different structural adhesives.
• Onur Sayman et.al conducted “Nonlinear stress analysis in adhesively bonded single-lap joint”.
Some structures are bonded by an adhesive due to simplicity of bonding and transferring
the forces easily. In this study, an elastic–plastic stress analysis is carried out in an adhesively-
bonded single-lap joint. The adhesive material was chosen ductile in order to obtain plastic
deformations.

7. Objectives of the project:
 In this project ,the single lap adhesive joint is formed by using CFRP composite
material With Araldite AW106 as an adhesive.
 Fabricate the specimen and perform tensile test by varying overlap length and by
keeping constant adhesive thickness.
 Fabricate the specimen and perform tensile test by varying adhesive thickness and by
keeping constant overlap length.
 To perform stress analysis and failure analysis using ANSYS for the above two
condition.
 Compare the experimental results with analysis result.

8. Methodology: Literature review
purchasing materials ,Adhesive
and hardener.
Fabricating layer by layer single
lap adhesive joint specimen
Cutting the specimen into
appropriate dimensions.
Testing of specimen experimentally
Analysis of specimen using Ansys
Comparison and Tabulation of results
Discussion and Conclusion

9. Dimensions and properties:
• The tensile properties of the CFRP materials were determined according to the ASTM
D5686. The width of all the members was 50 mm and the overlap length was 25 mm.
The thickness of the adherends was taken to be 3 mm, and the thickness of the adhesive
layer was 0.3 mm. Each adherends have 8 layer of carbon sheet.
• In the case of tensile loading of the joint, one end of the adherend was constrained from
x, y, and z translations, while the other end was constrained from y and z translations and
for validation and comparison purpose, a load of magnitude 7500 N similar to was
applied,
Figure 1: Geometrical model of the single-lap adhesive joint[1]

10. Material properties:
Carbon fiber /epoxy(adherend) E1= 50GPa,ⱱ21=0.3,G12=5GPa
E2=50GPa,ⱱ32=0.25,G23=3GPa
E3=7.2GPa,ⱱ31=0.25,G13=3GPa
Epoxy (adhesive) E= 2.8GPa,ⱱ=0.35,G=1.04GPa
σy=38MPa,σuts=40MPa,γuts=1.8%
Table 1: Material properties[1]

11. Ansys model:
Figure 2:Dimensions according to reference paper[1]

12. Figure 3&4:Fine meshing of model

13. Figure 5:Boundry conditions of the model

14. Validated results:
Figure 6: Equivalent stress(Von-Mises stress) after the load of
7500 applied on the model

15. Figure 7:Maximum stress is observed in the edges of overlap length

16. Figure 8: Maximum shear stress

17. • The stress developed at the mid-plane of the adhesive layer of the joint
was calculated as a function of overlap length, as shown in Fig. 6 and 8.
Since in the adhesive joints, the applied loads on the adherends are
transferred on to the adhesive layer mainly by shear and tensile stresses,
these two stresses were considered for the analysis. Table 2 ,shows the
results of the present analysis and the results obtained in [1].
• Figures 6 and 8 show the variations of shear and tensile stresses along the
adhesive length when the adhesive bond is subjected to the tensile
loading. Considering both the variations of the shear and tensile stresses,
it can be seen that the maximum values of the shear and tensile stresses
occurred near both ends of the adhesive region. But, toward the central
part of the adhesive layer, these stresses reduced in magnitude. The
magnitude of the shear stress decreased almost linearly from the edges
toward the center of the joint.

18. Table 2:Result
Parameter Present Work Reference
Tensile stress 47.23Mpa 41.64
Shear stress 26.239Mpa 29.30

19. References:
[1] S. M. R. Khalili & M. Mokhtari (2015) Numerical Study of Adhesive Single-Lap Joints with Composite
Adherends Subjected to Combined Tension–Torsion Loads, The Journal of Adhesion, 91:3, 214-234,
[2] Li G, Sullivan PL, НrLng RW (1999) Nonlinear finite element analysis of stress and strain distributions
across the adhesive thickness in composite single-lap joints. Composite structures 49: 395-403.
[3] Kumar RLV, Bhat MR, Murthy CRL (2014) Analysis of composite single lap joints using numerical and
experimental approach. J Adhesion Sci Tech 28: 893-914.
[4] Wang ZY, Wang L, Guo W (2009) An investigation on strain/ stress distribution around the overlap
end of laminated composite single-lap joints. Composite Str 89: 589-595.
[5] Andrews R, Jacques D, Qian D, Rantell T (2002) Multiwall carbon nanotubes: Synthesis and
application. Acc Chem Res 35: 1008-1017.
[6] Yu N, Zhang ZH, He SY (2008) Fracture toughness and fatigue life of MWCNT/epoxy composites.
Materials Sci Engg A 494: 380-384. 18. ASTM D (2004) Standard test method for lap shear adhesion for
fiber reinforced plastic (FRP) bonding, Annual book of ASTM standards.

20. THANK YOU