Multi-Material Ratchet-like Mechanism for Interlocking Joint Details

Interlocking is a concept that has been used throughout history around the world to create structures. It involves connecting pieces of a structure that have carefully designed geometry and material usage to enable stiff, strong joints without connectors like bolts or welds (Erman [1]). Despite the heavy use of such joints in traditional timber structures, interlocking joints are rarely used in buildings today. On the other hand, digital fabrication technologies have opened new possibilities to fabricate complex geometries that are often used in interlocking joints, without the need of highly skilled craftsmen. Multi-Material Additive Manufacturing (MMAM) is of our interest due to its capability to design material properties at a microscopic scale. In this context, our research takes a view that microstructure and its composition of every material, including that of wood, will be designed and custom tailored to improve its performance and reliability in the near future (Messler [2]; Messler [3]).

The specific paper presents the design and physical testing of a bespoke multi-material ratchet-like mechanism that can be applied to interlocking contact surfaces. Our mechanism allows easy insertion of two or more interlocking elements while preventing them to easily dislodge by controlling the material layout and geometry at the contact surface. In essence, the mechanism controls contact surface friction of interlocking joints by combining the principles of ratchet and compliant mechanisms. The mechanism was fabricated using MMAM and tested under two opposite loading directions. The results clearly indicate the effectiveness of our design.