ITIL: Interlaced Topologically Interlocking Lattice for continuous dual-material extrusion

Abstract

Extrusion (MEX) systems with dual-material capability can unlock interesting applications where flexible and rigid materials are combined. When chemically incompatible materials are concerned the adhesion between the two might be insufficient. Therefore researchers typically rely on dovetail type interlocking geometries in order to affix two bodies mechanically. However, dovetail type interlocking introduces extrusion discontinuities and relies on the material's resistance to deformation, which is difficult to model.We propose a simple and effective 3D lattice consisting of interlaced horizontal beams in vertically alternating directions which interlock topologically: the interlaced topologically interlocking lattice (ITIL). It ensures continuous extrusion and ensures an interlock even for highly flexible materials. We develop analytical models for optimizing the ultimate tensile strength of the ITIL lattice in two different orientations relative to the interface: straight and diagonal. The analytical models are applied to polypropylene (PP) and polylactic acid (PLA) and verified by finite elements method (FEM) simulations and physical tensile experiments. In the diagonal orientation ITIL can obtain 82% of the theoretical upper bound of 8.6 MPa. ITIL seems to perform comparably to dovetail interlocking designs, while it lends itself to application to non-vertical interfaces. Optimizing the lattice for non-vertical interfaces, however, remains future work.

Review on Additive Manufacturing of Multi-Material Parts: Progress and Challenges

“…The T-peel test also showed that the gradient pattern at the boundary region yielded much better peel resistance than the direct transition interface (62% higher in terms of both average peel force and energy release rate). Lately, Kuipers et al performed a new approach to design interfaces with an interlaced topologically interlocking lattice (ITIL) approach [179] as shown in Figure 16A-C. In this approach 3D lattice consisting of interlaced horizontal beams were created at the interface region by vertically aligning them so that they were topologically interlocked.…”

“…A storage box utilizing the straight ITIL variant. Images (A-C) were reprinted for free with no permission required under http://creativecommons.org/licenses/by/4.0/ through article (accessed on 20 November 2021) [179], (D) bicontinuous mesostructural geometry with compositional gradation in material extrusion [180], (E) designed interface patterns using voxelization method and fabricated by the FFF process, (F) gradient test sample showing higher interface strength, (G) fractured specimens, (H) direct interface of fused filament fabrication-made multi-material part that has a direct transition from ABS to polycarbonate (PC) material. Red arrows indicate the tension (loading) direction.…”

Xpandables: Single-filament Multi-property 3D Printing by Programmable Foaming

“…Multi-nozzle printing also limits the material combinations that can be used, as not all combinations are compatible. Bonding between two materials can be improved by an interlocking structure [16].…”

Mechanical Performance of Light Weight 3D Printed Interlocked Assemblies

“…It has been observed that elastic modulus was significantly improved. Kuipers et al [16] developed the performance of an interlaced topographically interlocking lattice using a dual material based material extrusion system. Ultimate tensile strength was investigated using different orientations.…”