Characterization of fracture behavior in adhesively bonded joints with porosity in the adhesive layer using X-ray computed tomography

Adhesively bonded joints with various levels of porosity in the adhesive layer are examined via X-ray computed tomography (CT) and Mode I fracture toughness testing. Bonded assemblies consisting of woven carbon fiber/epoxy composite adherends and a toughened epoxy film adhesive are considered. Porosity is induced in the adhesive layer through the use of shims during the manufacturing process. X-ray CT and accompanying image processing is used to characterize bondline thicknesses and void content in each Mode I fracture toughness specimen considered. Mode I fracture toughness tests are carried out to quantitatively assess the effects of porosity in the adhesive layer and post-test optical microscopy is used to examine the relationships between fracture toughness and fracture processes. This experimental approach is used to establish relationships among bondline thickness, void content, Mode I fracture toughness, and failure modes in an effort to correlate quantifiable physical parameters to adhesively bonded joint structural performance.