Tensile- and Shear-Strength Tests with Adhesive Connections in Dynamic Message Signs

Abstract

A dynamic message sign (DMS) is made up of a display, cabinet sheet aluminum skin, and internal structure along with electrical components. The aluminum skin is connected to the internal structure usually with a welded connection; however, adhesive or chemical bonding can be used instead for the connection between these two components. The goal of this paper is to examine the tensile and shear strengths along with other mechanical properties of adhesives used in the DMS under varying environmental and geometrical conditions. Adhesive tensile and shear specimens with different widths were tested according to accepted standards after conditioning them in different temperature and humidity conditions. Numerous data resulting from the tests were analyzed through graphical comparisons and statistical analysis so as to explore the effect of the considered parameters on tensile and shear strengths. As part of the statistical analysis, response surface metamodels (RSMs) were utilized not only to determine statistically significant parameters affecting the strengths, but also to develop separate regression models for the tensile and shear strengths. The highest decrement in the tensile stress was found to be 7.1%, 19.9%, and 7.9% with the increase in conditioning temperature, conditioning humidity, and specimen’s width, respectively. Owing to the effect of increases in conditioning temperature, conditioning humidity, and specimen width, the shear stress was increased most by 10%, 7%, and 19.3%, correspondingly. Key findings revealed that an increase in conditioning humidity decreases the tensile strength. The RSM model–based analysis also found conditioning humidity to be the most significant parameter negatively affecting the tensile stress because a probability value of 2.529% was observed from the RSM model. Finally, this work found adhesive or chemical bonding to be a possible substitute to welding for assembly of the DMS.