Page 97 - ESAM-1-1

Engineering Science in
Additive Manufacturing Mechanical property of metal-based IPC

of lattice structures is inherently linked to their geometric (FCCH). This innovative design paradigm harnesses
configuration and the properties of their constituent the superior strength of the rigid truss while employing
materials, which collectively determine their load-bearing ductile epoxy to mitigate buckling and facilitating uniform
and energy dissipation characteristics. 13,14 deformation under compressive loading. Consequently,
From a structural standpoint, various lattice under conservative conditions, the compressive strength
configurations have been designed to enhance mechanical of FCC, FCCR, and FCCH-IPCs is improved by 31.62%,
properties. Typical configurations include body-centered 36.06%, and 47.93%, respectively, compared to the
cubic 15-17 face-centered cubic (FCC), 18-20 and octet truss combined performance of their individual truss and epoxy
lattices, 21-23 each providing benefits in terms of stiffness, components. Furthermore, the specific energy absorption
strength, and deformation behavior. To further enhance (SEA) of these IPCs is increased by 153.54%, 99.77%,
performance, advanced topological configurations such and 141.36%, respectively, relative to their individual
as vertical strut arrangement, self-similar hierarchical truss lattices. These findings highlight the potential of the
architecture, density gradient, and hollow struts have been proposed IPCs to address the inherent trade-offs between
implemented. 24,25 The vertical strut arrangement strategy strength and toughness in conventional lattice structures.
involves reinforcing trusses with additional vertical struts, 2. Materials and methods
thereby increasing their local stiffness and resistance
to buckling. 26,27 Structural hierarchy entails embedding 2.1. Structure design
smaller-scale lattices into larger-scale frameworks, which Three FCC-based microlattice configurations are designed,
enhances energy absorption and delays the onset of failure encompassing conventional, vertical reinforced, and
by distributing stress more effectively. 28,29 These advanced hierarchical strategies, which are named FCC, FCCR, and
design strategies not only improve the mechanical FCCH, respectively. Their geometrical configurations are
performance of lattice structures but also enable precise illustrated in Figure 1A. The FCC configuration serves
control over their deformation. By redistributing stress as the baseline design, characterized by face-centered
9,30
and promoting more uniform deformation, these strategies struts and nodes. The nodes of FCC are susceptible to
can effectively delay the onset of localized failure modes, stress concentration phenomena, potentially leading
such as buckling or fracture. to premature failure and fracture. 26,37 To mitigate this
From a material perspective, the selection of constituent vulnerability, vertical reinforcement members are
materials is crucial in defining the overall performance of strategically incorporated in proximity to these nodes,
lattice structures. For pure material lattices, the intrinsic culminating in the FCCR configuration. To maximize
31
limitations of the constituent materials inherently create a the internal volumetric utilization of the FCC structure,
trade-off between the compressive strength and toughness a coupled design approach incorporating self-similarity
of the lattice metamaterials. Rigid materials, such as and embedding principles is employed. A scaled-down
25
titanium alloys, offer high strength and stiffness but are FCC geometry is constructed within the structure,
often constrained by their brittleness and vulnerability to with additional diagonal struts connecting the internal
fracture under compressive loads. 32,33 Ductile materials, framework, resulting in the FCCH configuration.
such as polymers and epoxy resins, demonstrate superior To ensure a fair comparison, the relative density of
ductility and energy absorption capacity, 34,35 but generally all three lattice configurations is kept constant at 19.4%.
lack the strength required for high-load applications When the cell length of the representative volume unit is
compared to rigid metallic materials. These trade-offs 6 mm, the corresponding strut diameters for FCC, FCCR,
underscore the necessity for innovative design paradigms and FCCH lattices are 1.14 mm, 1.00 mm, and 0.74 mm,
to address the limitations from constituent materials. 36 respectively. The IPC configurations are achieved by filling

To overcome these challenges, we propose a novel the external domain of truss members with epoxy. All
class of interpenetrating phase composites (IPC). The IPC truss and IPC metamaterials were fabricated with uniform
metamaterials integrate the rigid truss with the infiltrating overall dimensions of 24 × 24 × 24 mm, corresponding to
ductile epoxy, fostering a synergistic interaction between a 4 × 4 × 4 unit cell arrangement. The fabricated structures
the two constituent material phases. From the truss are shown in Figure 1C and D, highlighting the high fidelity
microlattice perspective, we incorporate ribbed strut of the manufacturing process. The measured masses
strategy and structural hierarchy into the FCC lattice and their corresponding standard deviations within the
framework, leading to the development of FCC vertical 95% confidence interval for the FCC, FCCR, and FCCH
reinforcement truss microlattice metamaterial (FCCR) trusses were 13.101 ± 0.023 g, 13.442 ± 0.209 g, and 13.708
and FCC hierarchical truss microlattice metamaterial ± 0.816 g, respectively. For the IPC counterparts, the

Volume 1 Issue 1 (2025) 2 doi: 10.36922/esam.8554