چكيده به لاتين
Abstract:
In the current research, a method based on the concepts of the theory of critical distances has been developed to predict the failure loads of adhesively bonded single lap joints (SLJs). The proposed method could predict the static failure load of single lap adhesive joints containing nano-particles. However, a variety of adhesives including the very stiff, ductile and moderate adhesives without any additive and the adhesives including micro-particles were also considered in this study. According to the proposed model, failure is expected when the longitudinal strain along the adhesive mid-plane reaches a critical value at a specified critical distance. The critical distance and the critical value of the longitudinal strain are both determined experimentally. The model was verified and the effect of material and geometry on the model constants were also analyzed by performing a series of experiments on single lap adhesive joints with different geometries. It was also validated by considering the experimental results reported by other researchers. Totally, more than 200 different configurations of single lap adhesive joints were studied in this work. According to the results, it was found that the critical distance is not affected by the joint geometry. However, the critical longitudinal strain is only affected by the adherent thickness. Although, the effect of adhesive thickness on the joint strength is a challenge, however, the proposed method was also able to consider the effect of bondline thickness on the joint strength. The proposed method was also applied on the joint containing micro cork particles and carbon nano tubes. Good correlations between the predictions and the experimental results were seen. The analysis of the SLJs with moderate adhesives (adhesive with elongation less than 10% and the Young’s modulus less than 4GPa) also showed that the there is a relation between the joint properties and the critical longitudinal strain. Accordingly, only one experiment is needed to obtain the constants of the proposed method. The most important advantages of the proposed criterion are as follows:
Very good failure load predictions, only a simple 2D linear elastic analysis, no sensitivity to mesh size, applicability on the joint with variety of adhesives including ductile, brittle and moderate adhesives, applicability on SLJs with adhesives containing nano- and micro-particles, the same critical constants for the joints with different geometries, obtaining the critical longitudinal strain by the material properties and the geometrical dimension of the joint without performing any experiment.
Keywords: Single lap adhesive joints, Critical distance, Longitudinal strain, Failure load prediction, Carbon nano tubes.
