Page 102 - ESAM-1-1

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

Figure 3. Captured deformation sequence of IPC metamaterials captured during the experiment, highlighting distinct collapse patterns for different
configurations.
Abbreviations: FCC: Face-centered cubic; FCCH: FCC vertical reinforcement truss microlattice metamaterial; FCCR: FCC hierarchical truss microlattice
metamaterial; IPC: Interpenetrating phase composite.

metamaterials. Figure 4A-C present a direct comparison compared to the IPCs, they suffered a significant loss in
of the engineering stress-strain curves for FCC, FCCR, their energy absorption capacity due to their brittle failure
and FCCH-IPCs against their corresponding pure mode.
Ti-6Al-4V trusses of equal mass. The results reveal distinct To elucidate the underlying strengthening-toughening
differences in the mechanical responses between the IPC mechanisms responsible for the superior mechanical
metamaterials and the pure metal trusses, underscoring properties of IPC metamaterials, we analyzed the
the superior performance of the IPC designs. deformation and failure behaviors of both truss and IPC
The pure truss lattices exhibit similar stress-strain metamaterials under compressive loading. The lightweight
characteristics, as summarized in Figure 4D-i. After an truss lattice consists of slender struts arranged in a specific
initial linear elastic region, the stress reaches a peak load, spatial topology, allowing for high porosity and low density.
corresponding to the maximum load-bearing capacity of Although this design enables efficient load distribution
the truss lattice. Subsequently, the truss lattice undergoes under elastic deformation, the slender struts often fail to
sudden failure, accompanied by a significant drop in deform uniformly during compressive loads. When the
load. In contrast, the IPC metamaterials demonstrate a applied load exceeds a critical threshold, the struts undergo
markedly different mechanical response, as illustrated inelastic buckling, as illustrated in Figure 4D-ii and iii. The
in Figure 4E-i. After reaching the yield point, the IPC critical buckling load, denoted as P , can be expressed as:
cr
metamaterials transition into a stable and controllable
post-yield softening mode, characterized by a relatively P 2 EIl/ 2 (VI)
smooth and extended plateau region in the stress-strain cr eff
curve. The comparison of compressive strength between
the IPC metamaterials and the pure truss lattices may Where E represents Young’s modulus of the matrix
initially appear counterintuitive, material, I denotes the moment of inertia of the cross-
section, and l is the effective length of the strut. Buckling
eff
m = m + m , instability reduces the load-bearing capacity of the truss
>> σ ,
σ , Pure Ti−6Al−4V truss IPC(Ti−6Al−4V truss) IPC(porous epoxy)
(V)
C Ti−6Al−4V C epoxy lattice, as the lateral deflection of the struts induces localized
At the same mass, the pure truss lattice is expected to stress concentrations. These stress surges render the rigid
exhibit significantly higher strength, as the weaker porous struts more susceptible to fracture, ultimately leading
epoxy in IPC accounts for a substantial portion of the to catastrophic collapse. This phenomenon represents
weight and volume. However, while the pure metal trusses a key limitation of pure truss microlattices, as buckling
exhibited only a slight advantage in compressive strength significantly undermines their mechanical performance.

Volume 1 Issue 1 (2025) 7 doi: 10.36922/esam.8554