Interlocking Strength, Failure Modeling, and Adhesion Optimization of DED-Fabricated Pins in Polymer–Metal Hybrid Interfaces

This study investigates the mechanical performance of interlocking patterns printed on metallic substrates under separation conditions. The polymeric parts (PEEK and Trogamid) were joined to metallic counterparts via axially symmetric mushroom-shaped interlocking structures. These structures were fabricated through the direct energy deposition process, with variations in the laser power and dwell time. The mechanically interlocked samples were evaluated via uniaxial pull-out separation tests, and apparent stress values were calculated from force-displacement curves. Our results demonstrate that pin geometry, size, shape, and surface density significantly influence the separation force. We developed models for the failure modes of polymer rupture (Mode 1), metallic pin fracture (Mode 2), separation by shear stress (Mode 3), and separation without fracture (Mode 4). These models enabled the formulation of a systematic design method for optimizing interlocking structures based on the basis of pin density and geometrical parameters. The experimental findings align closely with the mathematical models, validating the predicted separation stress values.