Epoxy nanocomposites for enhanced fire retardancy and metal-to-metal bonding properties of aircraft aluminum alloys
Abstract
Epoxy adhesives have a wide range of applications in aerospace, automotive, marine, and
construction industries. Epoxies reduce the weight of a structure by minimizing fasteners. By
application of epoxy adhesive, a structure can achieve uniform stress distribution, structural
integrity, durability and cost effectiveness. A mechanical weakness of epoxy adhesives is their
lack thermal stability and failure at post-curing-cycle temperatures. Fire retardancy can be
improved by incorporating graphene nanomaterials as reinforcements. These graphene additions
have potential to improve the epoxy's thermal, mechanical and electrical properties. The epoxy nanocomposites of different weight percentages of graphene nanomaterials
were prepared using a three-roll milling machine, Single-lap, shear-strength tests were carried out
for evaluating the mechanical properties of the epoxy using a tensile test method. The flame
retardancy values for the epoxy nanocomposites were determined using the ASTM UL-94 vertical
burn tests. The thermal characterization of the epoxy nanocomposites was carried out using
thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). Surface
morphology analysis was carried out for epoxy nanocomposites by using scanning electron
microscopy. The test results showed that fire retardancy was improved by 3wt% and 5wt% with
graphene nanomaterial inclusions when compared with pristine epoxy. The DSC results, when
compared to 0.5wt and 5wt% graphene inclusions showed the glass transition temperatures
increased by 6.2%. The TGA results showed a decrease in mass reduction by 6.2%, due to
inclusion of graphene nanomaterials. The lap shear strength when tested under tensile tests were
improved by 27%, compared to pristine epoxy. Thus, graphene nanomaterial inclusions improved
both mechanical and thermal properties while increasing thermal stability of the epoxy when
compared to pristine epoxy.
Description
Thesis (M.S.)--Wichita State University, College of Engineering, Dept. of Mechanical Engineering