Estudo da utilização de adesivo estrutural para redução de pontos de solda nas partes móveis de veículos e correlação da estrutura do compósito metal/recobrimento/adesivo formado com seu desempenho mecânico

Abstract

The Brazilian automotive industry subjected to a broad internal and external competition is forced to look for alternatives to improve its productivity, decrease its costs and keeping performance and quality requirements of the market. Driven by this scenario, the use of structural adhesives for joining metals is growing significantly in this industry. The adhesives allows the elimination or reduction of other forms of union as weld, rivet and bolt, making the process more streamlined and productive. Weld application is a costly process on automotive productive chain and can also impact on the vehicle life time. Welding is complex and affects the aesthetics of the components and the performance of the material which becomes more susceptible to corrosion and more fragile. The moving parts of the vehicle doors, hood and trunk lid are composed of two metal plates joined by structural adhesive and spot welds. After the welding they should be submitted to repair process, in order to improve their surface finish. In this work, the composites metal/coating/adhesive formed in body shop are composed: steel and aluminum as metal, zinc and/or phosphate as steel coatings and single-component epoxy base structural adhesive and a two-components acrylic base as adhesives. The current manufacturing process of the vehicles moving parts and the relationship between the structure and mechanical performance of the composites metal/coating/adhesive, before and after durability tests, were studied. Technical visits and evaluations of process were made in 7 Brazilian OEM and 3 foreign OEM. Tests of roughness, surface tension, SEM/EDS, DMA and TG allowed characterizing the composites structure and their constituents. While, the mechanical performance was evaluated by single lap shear tests before and after salt spray, humidity and heat. The result of this work is a process proposal more streamlined, productive, with lower cost, with elimination of the spots weld by using single-component and two-component structural adhesive. In additional, in this work were published information that can facilitate new metal products development bonded by structural adhesives for the automotive industry.