  Thick adhesive layers have potential structural application in ship
construction for the joining of a composite superstructure to a steel hull. The
purpose of this study is to develop a mechanics model for the adhesive fracture
of such lap joints under shear loading. Modified Thick-Adherend-Shear-Test
(TAST) specimens made from a MMA-based adhesive and steel adherents are
designed and fabricated. Crack initiation and growth of these joints is
measured and monitored by Digital Image Correlation (DIC). An attempt is made
to use a cohesive zone model to predict the magnitude of shear strain across
the adhesive layer both at crack initiation and at peak load, and to predict
the extent of crack growth as a function of shear strain across the adhesive
layer. The ability of a cohesive zone model to predict several features of
specimen failure is assessed for the case of an adhesive layer of high shear
ductility.
