Tuning energy dissipation in damage tolerant bio-inspired interfaces

Tuning interfacial behavior is very desirable in many engineering applications, including adhesive bonds in composite materials, advanced biomedical tools, and metamaterials. Recent experimental work has shown that modifying the sub-surface region of an interface is a viable strategy to control the structural response. The effect of buried cylindrical hollow channels, mimicking the base plate of the Amphibalanus (=Balanus) amphitrite, was assessed on a model material system comprising adhesively bonded 3D printed polyamide substrates in the Double Cantilever Beam (DCB) configuration. Beneficial crack-trapping effect and remarkable enhancement of the total work of separation were reported. The present work supplements our experimental study with an extensive series of finite element analyses (FEA) of crack growth using interface elements. The simulations were able to mimic the serrated behavior observed in experimental load-displacement responses, which was due to snap-through interfacial cracking, i.e., a sudden and almost instantaneous growth of apparently stable cracks. Since we expect that specific geometrical properties of the channels play an essential role in the mechanical behavior of the joint, a parametric investigation was herein carried out to ascertain their effect on the work of fracture. The results show that the channels aspect ratio and pitch play a fundamental role and may allow to tailor the dissipated energy needed to sever the interface. Ancillary experimental tests, carried out on 3D printed DCBs adhesive joints, support the results of the finite element simulations and allow us to pinpoint the effect of channel geometry on the mechanisms of crack growth.