Abstract
In recent years structural adhesives technology has demonstrated great potential for application due to its capacity to transform complex structures into solid unitary and monolithic assemblies using different materials. Thus, seams or joints integrate these structures providing, besides a reduction in weight, a considerable increase in the mechanical resistance and stiffness. The increase in the industrial use of structural adhesives is mainly due to their ability to efficiently bond different materials in an irreversible manner, even replacing systems involving mechanical joints. In the automobile industry structural adhesives have been widely used for the bonding of metal substrates, thermoplastics and composites, frequently employing these in combination, particularly glass fiber and polyester resin composites molded using RTM and SMC processes. However, the use of urethane structural adhesives in applications involving composites and thermoplastics has been the subject of few investigations. In this study the effects of temperature and time on the shear strength of RTM, SMC and ABS joints, applying temperatures of -40, 25, 80, 120 and 177 °C and times of 20 minutes and 500 hours, were determined. The objective was to evaluate the performance under extreme conditions of use in order to assess whether these joints could be used in passenger or off-road vehicles. The results showed that the urethane structural adhesive promoted the efficient bonding of these materials, considering that due to the high adhesive strength the failures occurred in the substrates without adversely affecting the bonded area. For each test condition the joint failure modes were also determined.
Highlights
The demands of modern industries such as those of the automotive, aeronautic and shipbuilding sectors, where there is a strong commitment to increasing productivity, with requirements for high quality indices, have lead to an ever increasing use of structural adhesives on their assembly lines
The objective of this study was to investigate the capacity of the urethane structural adhesive to replace the use of mechanical joints with adhesive joints and to demonstrate that the adhesive is as or more efficient than the mechanical joint
For the ABS specimens the shear strength was lower than the values obtained for the SMC and RTM, which can be interpreted as a natural occurrence considering that ABS has a lower tensile strength than the composites
Summary
The demands of modern industries such as those of the automotive, aeronautic and shipbuilding sectors, where there is a strong commitment to increasing productivity, with requirements for high quality indices, have lead to an ever increasing use of structural adhesives on their assembly lines. The advantages offered by structural adhesives in relation to traditional mechanical joints, such as welds, rivets or screws, include the possibility to bond distinct materials with different thermal expansion coefficients, obtaining monolithic structures which are mechanically extremely resistant 1. The automotive industry, in particular, has evaluated new materials aimed at attaining better vehicle performance and structural adhesives have contributed to this objective, permitting the bonding of traditional metal materials with polymeric materials and composites, and the bonding between these types of materials themselves. The bonding of parts using structural adhesives offers significant benefits in relation to traditional systems. The adhesive distributes the loads and stresses acting on the total
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