On the Effect of Temperature upon the Shearing Strength of Adhesive-Bonded Composite Material

Abstract

As adhesives become strong, the chances that they are used in constructions have recently increased. Above all, adhesive-bonded composite materials, as shown in Fig.1, made of different kinds of materials are applied in the field of ship equipment. So, it seems to be most important to examine the effect of temperature upon the strength of these objects. When these pieces are given a certain steady-state temperature, because of the difference of coefficients of linear expansion, shearing stress occurs in the adhesive layer and it becomes the main cause for the damage of these pieces. In this paper, the distribution of this adhesive shearing stress is solved by an analytical method, based on the assumption that adhesives are elastic in low temperatures. The relation between the temperature that makes the shearing stress at the facing surfaces of these pieces the ultimate shearing strength and their lengths is obtained, and compared with experimental results. Besides, for the case that there are un-adhesive parts in the adhesive layer, shearing stress is obtained. And the effective adhesive length is examined. In order to minimize the maximum shearing stress, two kinds of adhesive are used in the adhesive layer and the distribution of shearing stress in this case is obtained. Results are as follows; 1) Adhesive shearing stress is proportional to both the temperature and the difference of coefficients of linear expansion in the layers. 2) Adhesive is not damaged below a critical temperature: [numerical formula] Therefore, this critical temperature may be used as the criterion of the design. 3) Effective adhesive length: l_e is approximated by the following equation at g_3≦1.5: [numerical formula], where β≧3, β=√<(g_4)(g_3)>l. (4) In the case that two kinds of adhesive are used, the maximum shearing stress can be made less than in the case of one kind of adhesive and it can be minimized, if shear modulus ratio and mutual boundary situation of the adhesives are properly chosen.