Fractographic analysis of the hygrothermal effect in co-bonded and secondary bonded joints under mode II delamination loading

Abstract Adhesive bonding technologies exhibit several advantages over conventional mechanical fasteners which include lower weight, reduced stress concentration in the adherents and excellent fatigue properties allowing the design of smooth surface contour and damage tolerant aerostructures. The overall structural performance of the composite joint depends on several factors related to the manufacturing process, such as surface preparation procedure, adhesive type, aging effects, and deficiency of inspection procedures. For this reason, there is a clear need to understand better how the joints behavior can be affected by them and the causes of their failure in order to improve the design and performance. In this context, this work presents the application of Scanning Electron Microscopy (SEM) technique to perform the fractographic analysis in two different types of joints namely co-bonded (CB) and secondary bonding (SB) that were submitted to a interlaminar fracture toughness tests under Mode II loading at Room Temperature Ambient (RTA) and Environmental Temperature Wet (ETW) conditions. The fracture surface of each sample submitted Mode II was prepared and analyzed regarding its failure aspects, enabling their association with the mechanical behavior of the samples during the fracture toughness tests and the values obtained. A detailed study on the fracture aspects of the composite joints was carried out correlating the fracture aspects with the mechanical behavior, type of processing and environmental conditioning in which each type of joint was tested, thus validating the use of these joints for operating conditions similar to those experienced in-service concerning aeronautical applications.