Adhesive Bonding of Composites

Polymer matrix composites have shown improved properties over traditional materials especially when considering weight normalized properties such as specific strength and stiffness. While this has been known for some time, the implementation of composites as structural materials still have complications due to limitations in bonding and fastening complex geometries.  Currently, composite panel bonding is completed primarily through the drilling of holes in critical locations within the panel and securing with the use of fasteners such as rivets and bolts. The mechanical fasteners link multiple panels together and also provide an added level of protection by mechanically limiting propagation of failure originating near the bond in the panel itself. While this process is effective there is a significant weight cost; both in the additional weight of the fasteners and also in increased composite thickness to combat failure. As such, the manufacturing of the necessary hole geometries has significant implications for overall performance, resulting in elevated stress concentration levels and delamination in the composite panel. Mechanical fasteners have lead to significant over-design and a loss in overall efficiency gained from the improved specific properties.

Our lab has multiple projects investigating the possibility of using adhesive bonding of as a method of joining composite parts. While the potential of adhesively bonding composite parts allows for the creation of extremely complex geometries without damaging the composite panel and with drastically reduced stress concentrations, challenges still exist. First, there is currently no accepted method to assess a bonded composite’s health or performance without without concurrently breaking the bond, and second, there is are only limited studies on the overall durability of bonded composite systems subject to the harsh environments of typical use. Our current efforts focus on these two challenges, along with the assisting in the education of composite manufactures and end-users on bus practices through assisting in the editing of the Composites Materials Handbook Ver. 17.