ONE APPROACH TO THE SPECIFICATION OF ADHESIVE PROPERTIES OF ADHESIVE JOINTS
Franjo Matejiček, Mirjana Lucić
University of Osijek, Faculty of Mechanical Engineering
Trg Ivane Brlić-Mažuranić 18, HR-35000 Slavonski Brod, Croatia
1. IntroductionAdhesive bonded joints have wider and wider application in home and world industry. Adhesive joints are the most using for bonding of automotive and airplane parts, but also in everyday life (industry of shoes, bookbinder, household…). Adhesives are versatile and offer a number of advantages over fastening techniques, however, there are number of limitations associated with their use.
Therefore, the investigations of influence of different factors on adhesive joint strength are incontrovertible. Beside of all influencing factors on adhesive joint strength (properties of adhesive, properties of adherend material, bonding procedures, joint design and loading conditions), of special importance is adhesive mechanical properties.
Single lap adhesively bonded joint will be considered in this paper as one of the most applied joint design in engineering practice.
Figure 1. Single lap joint specimen [1]
Joints are made with three adherend materials (aluminium, brass and stainless steel) and one type of adhesive: two component high-strength engineering adhesive. Such prepared joints have been stretched up to the break in the jaws of the tensile testing machine.
It was investigated more lapping areas on all of adherend types [1]. Table 1 shows mechanical properties of materials used for investigation.
Table 1. Mechanical properties of materials
ADHESIVE(N/mm2) / ADHERENDS (N/mm2)
Al99.5 / X5CrNi18-10 / Ms60
E = 4000 / E = 70000 / E = 200000 / E = 100000
Rp0,2 = 103 / Rp0,2 = 190 / Rp0,2 = 200
m 113 / m 430 / m 400
= 0,35 / = 0,33 / = 0,3 / = 0,3
2. Experimental research
The standard single lap specimens for evaluating the load bearing characteristics i.e. strength of adhesively bonded joint have been prepared accordingly Figure 1. Dimensions of prepared adherend plates were a×b×s=30×90×1,95 mm (30×90×1,50 for brass only). The adherends are cleaned by an appropriate surface preparation method [2].
This paper deals with the phenomenological approach of determination of adhesive characteristics in adhesive joints. The major idea of authors is that by describing of adhesive properties E and ν are continuous, and Re and En’ (tangent modulus of n material) are changing. An assumption is that adhesive forces strongly depend on materials which have to be bonded and influence on different behaviour of adhesive.
The basic idea how to describe stress and strain data needed for numerical model is qualitatively depicted on the Fig. 3. These data are presented also quantitatively in the Table 2.
Figure 2. True stress-strain diagram for adherends
Figure 3. Stress-strain diagram of adhesive
Table 2. Hypothetical data for adhesive parameters
15 / 20 / 30 / 40
Adherend / X5CrNi18-10 / 10/28 / 4/26 / 4/15 / 3/12
Ms60 / 4/12 / 3/10 / 2/6 / 2/5
Al99.5 / 4/10 / 4/9 / 4/6 / 3/5
Hypothetical data are involved into the numerical model od adhesive joint and simulation of loading performed by using of commercial ANSYS software [3]
Some of results of simulations (state of testing are shaded in table 2) are presented on figures 4-8 and compared with experimental results.
Figure 4. Comparison of exp. and numerical results
(adherend: brass; lap length: 15 mm)
Figure 5. Comparison of exp. and numerical results
(adherend: aluminiums; lap length: 30 mm)
Figure 6. Comparison of exp. and numerical results
(adherend: aluminium; lap length: 40 mm)
Figure 7. Comparison of exp. and numerical results
(adherend: stainless steel; lap length: 20 mm)
Figure 8. Comparison of exp. and numerical results
(adherend: stainless steel; lap length: 40 mm)
Experimental analysis of adhesive joints has shown that bonding of different adherends with the same adhesive leads to the different behaviour of adhesive. This effect is more evident by numerical modelling of such joints, especially by bonding of adherends with greater mechanical properties. Actually, the problem is in missing proper data of adhesive, because it is possible to obtain the cohesion strength of adhesive only.
Using of hypothetical data for adhesive and comparison of numerical and experimental results has shown that this approach may be successful.
The phenomenon of adhesive properties dependence on the lap length and adherend material has to be more investigated in the future to be able to predict adhesive behaviour more real.
References[1] Matejiček, F., Raos, P., Lucić, M.: “Numerical Analysis of Single-Lap Adhesive Joint”, Proceedings of the 4th International Congress of Croatian Society of Mechanics, Bizovac, Croatia, 2003., pp 323-330.
[2] N.N., “Technical Data Sheet, Product 3421”, Loctite Corp., Dublin, 2000.
[3] ANSYS 6.0, 2002
[4] DIN EN 1465: Klebstoffe-Bestimmung der Zugscherfestigkeit hochfester Überlappungsklebungen (ISO 4587:1979 modifiziert) Deutsche Fassung EN 1465: 1994.