My research is focused on design and evaluation of metal and composite joints, including chemical bonding design, mechanical evaluation, long-term reliability, and intrinsic toughness G0 measurement of joints, which can be used as a failure criterion for designing joints in service.

Enhanced chemical bonding is accomplished by applying the technology of a self-assembled monolayer by depositing a silane layer on adherend surfaces. All joints are mechanically evaluated by measuring the joint fracture energies, Gc, using the double cantilever beam (DCB) experiment. Effects of moisture and seawater on Gc of joints are experimentally investigated to assess the long-term joint reliability. The increased water-resistance-ability of the joints with employing self-assembled monolayer is experimentally approved.

Fracture energy of joints at cryogenic temperature is also measured by using the DCB experiment equipped with a cryogenic cell to estimate the intrinsic toughness G0 of joints. Further, joint characterization by using a laser-generated stress wave will be accomplished. Energy dispersive X-ray spectrometry and scanning electronic microscopy experiments are conducted to identify all failure loci of post-fractured surfaces of joints.

Tantalum/sapphire interface was chosen for understanding the microstructural basis for the intrinsic strength, intrinsic toughness of interfaces and its relation to the plastic work that accompanies interface decohesion. Effects of extrinsic parameters, including the film, substrate microstructure (orientation and roughness), and temperature, on interfacial tensile strength and intrinsic/total fracture energies were determined.