The role of adhesive–adherend interface morphology (through intentional deviation from aflat joint
plane) on the mechanical behavior of adhesively bonded lap joints is studied. Two mirror-image types of
joints with a zigzag interface containing ‘positive and negative’ interlocking teeth were fabricated and
their tensile behavior was measured and compared to the response of a standardflat joint. Numerical
simulations were used to explore the role of tooth height and width on the stress distribution in the
adhesive, and on crack propagation and arrest after initial fracture. The data suggest that stress
distribution along the bond line–and thus, the initial fracture load of the joint–is altered considerably
by the positive and negative interlocking teeth. The tendency of a crack to either propagate along the
bond or to arrest also depends strongly on morphological details. When crack arrests, the bonded joint
can sustain a higher load and thus benefits from some of the intrinsic properties of the adherends (e.g.
the plasticity of metal adherends) to enhance energy absorption and toughness. Our findings provide
insight for the development of robust multi-material and multi-component structural systems with
tailorable properties, and for understanding the role of interface morphology in some biological systems