Nature employs complex interlocking geometries, such as vertebrate cranial sutures, to combine load transfer with localized compliance and geometric interlocking. These biological interfaces incorporate alternating wide regions and narrow necks that can accommodate localized deformation while maintaining mechanical interlocking. Inspired by these structural characteristics, digitally fabricated timber systems—such as Skylark–WikiHouse assemblies—can employ analogous bow-tie joint geometries to introduce controlled compliance into the connection. While conventionally manufactured from plywood, the translation of this bio-inspired geometry using hybrid thermoplastic–timber materials remains insufficiently explored. To address this gap, hybrid bow-tie joints comprising 18 mm radiata pine plywood panels and compression-molded polypropylene (PP) or high-density polyethylene (HDPE) connectors were evaluated. Ten joints underwent displacement-controlled monotonic tension at 2 mm/min. The results indicate that PP and HDPE joints achieve nearly identical mean maximum loads of 6.61 and 6.65 kN, respectively. However, substituting PP with HDPE significantly alters the global load–displacement response, yielding 33% lower global stiffness, 63% greater displacement at maximum load, and 70% greater external mechanical work. Post-test examinations revealed that final visible cracking was localized to the surrounding plywood, with no complete rupture of the thermoplastic connectors. This final damage localization is consistent with the intended suture-inspired design concept; however, the present post-test observations do not establish the temporal sequence of crack initiation and propagation or directly demonstrate crack arrest. These findings identify connector material as a practical bio-inspired design variable for tuning the global stiffness–deformation response of digitally fabricated timber joints while maintaining comparable maximum tensile load capacity.

Integral CNC-machined timber connections provide an efficient fastening-free solution for digitally fabricated modular construction systems. Their response under repeated loading is governed by the interaction between joint geometry, plywood architecture, contact, and progressive material damage. This study experimentally investigates the quasi-static cyclic response of full-scale TIE joints used in the WikiHouse Skylark system and manufactured from 18 mm Pinus radiata D. Don plywood. Three plywood configurations were evaluated: standard structural plywood (STD), weather-resistant plywood (HR), and fire-resistant plywood (FR), with the central TIE element oriented either parallel (//) or perpendicular (⊥) to the applied load. A displacement-controlled cyclic protocol adapted from ISO 16670 was applied. The exploratory cyclic program used one full-scale specimen per tested configuration ($n=1$), comprising six tensile configurations and three shear configurations. Tensile joints were subjected to one-sided loading–unloading cycles, whereas shear joints were subjected to reversed cyclic displacement. Under cyclic tension, maximum forces ranged from 6.082 to 9.794 kN at displacements between 6.6 and 10.3 mm, with the highest measured force obtained for the HR ⊥ configuration. Reversed cyclic shear tests produced maximum forces between 8.212 and 8.976 kN at displacements between 4.7 and 7.0 mm. Across all tested configurations, the apparent initial stiffness ($K_e$) ranged from 1.202 to 1.641 kN/mm, while the cumulative dissipated energy ($E_d$) ranged from 105.02 to 425.81 J. Damage consistently localized within or adjacent to the reduced central TIE region and involved combinations of tensile cracking, shear fracture, local crushing, fiber separation, and fiber rearrangement. The results show that the integral TIE geometry maintains a well-defined load-transfer and failure region under progressively increasing cyclic displacement. The experimental evidence provides a component-level basis for subsequent replicated testing and the development of nonlinear models of digitally fabricated plywood connections.