The purpose of this research study is to analyse the effect of the design of mechanical fastener on their effectiveness as Disbond Arrest Features (DAFs). This was done by means of a sensitivity study using a 3D model using the Virtual Crack Closure Technique (VCCT) to model the disbond growth of a single lap shear specimen comparing the Strain Energy Release Rate (SERR). Different fastener material stiffnesses, shaft radii, head radii and head geometries were compared. The sensitivity study showed the Mode I SERR was completely independent of the fastener design and the Mode II was suppressed more strongly for fasteners with a lower flexural flexibility. Fasteners with a countersunk head showed less reduction of the Mode II SERR, this was caused by the head rotating as a result of the fastener adherend interaction, reducing the effectiveness of the load transfer.