Issue 48

M. Bezzerrouki et alii, Frattura ed Integrità Strutturale, 48 (2019) 491-502; DOI: 10.3221/IGF-ESIS.48.47 495 The analysis of the stress distribution in the bonded assemblies is essential in order to predict the level of stress intensity for each substrate. Almost all the applied load will be transmitted to the adhesive which is the weak link of the structure seen these weak mechanical properties comparing to those of the plates. The adhesive will be subjected to a set of stresses, mainly the shear and peel stresses caused by the non-linearity of the two forces. One exposed the Fig. 6 to explain the difference of stresses between the zones A and B. The stress distribution is not symmetrical because the two edges of the adhesive are not included at the same zone of the plate. Fig. 6a shows an example of Von-Mises stresses distribution for an applied stress of 20 MPa for Model 1. The stress distribution in the adhesive layer for the single lap joint is not homogeneous. In our study the stress distribution was determined along the AB segment on the adhesive / plate contact area represented in the Fig. 6b. Noting that the points A and B represented the zones A and B respectively. The point A is on the free side at the edge of the adhesive and the plate, so we have high stresses due to the edge effect. On the other side, the point B is on the plate and at the limit only of the adhesive where the stresses are lower compared to the point A. (a) (b) Figure 6 : (a) Von-Mises stresses distribution, (b) Representation of zones A et B. Study of the stress distribution for model 1 One knows that the area stressed in the adhesive increase proportionally with applied stress and it is the same for the shearing and peeling stresses. Fig. 7 shows the variation of Von-Mises stress, shear and peel stresses at the adhesive layer. One note that shear stresses remain almost low than Von-Mises and peel stresses. We clearly notice that whatever the value of the applied stress is the stress concentrations are localized at the edge adhesive layer. The depth of the adhesive remains inactive for low stress applied. An applied stress of 10 MPa generates a stress of 15 MPa in the adhesive. While the increase of the stress applied to 20 MPa generates almost 30 MPa what causes a degradation of the adhesive and makes work in its field of rupture. The bending moment caused by the nonlinearity of the forces causes high values of peel stresses, since the overlap length is minimal comparing to the lengths of the plates. Inactive area Zone A Zone B