Adhesive bonding of composite structures in aircraft are prone to impurities at the joint interface. Because of these impurities, the Federal Aviation Administration (FAA) governs adhesively bonded joints strictly and requires destructive mechanical testing. To comply with the FAA mandates, aircraft manufactures use mechanical fasteners for load path transmission. These fasteners lead to increased aircraft weight, higher costs, and longer manufacturing times. In preceding work, a technique called AERoBOND was developed with the objective to develop secondary bonded composites using a latent cure. Utilizing off-stoichiometric epoxy matrix resins to produce a joint interface that remains reflowable through a secondary bond, it aimed to produce properties like a co-cured joint. Succeeding AERoBOND, AERoBOND+ was developed to alleviate the strict manufacturing tolerances of the AERoBOND process, with adhesive serving as a gap filler. This study examined the implementation of both the AERoBOND and AERoBOND + process in a co-bonding scenario, promoting adaptability to additional manufacturing scenarios. Distinct processing parameters for panels were assessed to accurately compare the co-bonded laminates. The joining interfaces of each panel were ultrasonically inspected and examined with a microscope to obtain insight on the effectiveness of the bond. ASTM International standard tests were implemented on specimens to quantify the mode-I and mode-II interlaminar fracture toughness. The joining interface of the AERoBOND + co-bonded panel propose properties that are proportionate to a co-cured joint. Regarding overall interlaminar fracture toughness, the AERoBOND + co-bonded panel outperforms a co-cured joint.
Hudson et al. (Wed,) studied this question.