Page 101 - ESAM-1-1

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

m < m + m , σ > σ + σ , (IV) epoxy resin allows for controlled deformation and delays
IPC truss solid epoxy C,IPC C,truss C,solid epoxy
Where σ represent the compressive strength of the the onset of structural instability.
C
structures, respectively, as indicated by their subscripts. This As compression progresses, notable differences in
inequality underscores the superior load-bearing capacity shear deformation patterns emerged among the three IPC
of IPC metamaterials. Figure 2H shows that the SEA of IPC configurations, driven by variations in their configuration
metamaterials is significantly higher than that of the pure designs. The FCC-IPC exhibited inclined shear bands,
metal truss microlattices. Specifically, the FCC, FCCR, and with shear deformation propagating from the top edges
FCCH-IPCs configurations exhibit SEA enhancements of on both sides toward the bottom center. In contrast, the
153.54%, 99.77%, and 141.36%, respectively, compared to FCCR-IPC exhibited vertical bar-shaped shear bands. In
their corresponding truss counterparts. This improvement addition, microcracks began to form earlier in the FCCR-
is attributed to the synergistic interaction between the IPC, causing the loss of connectivity between struts in
strength of the metal truss components and the ductility of localized regions and resulting in a more brittle failure
the epoxy resin within the IPC metamaterial. mode. With further strain, the fractures in the FCCR
The Ashby plot is presented in Figure 2I to compare metal struts became more pronounced, accompanied by
the compressive strength and SEA of the proposed localized tearing of the epoxy resin matrix. This ultimately
IPC metamaterials with various existing materials and led to the formation of prominent vertical fracture bands
structures. The materials included in the comparison are that propagated throughout the metamaterial. The vertical
316L vertical-reinforced lattices, 316L plate lattices, 316L fracture bands and global collapse significantly diminished
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bio-inspired vertex modified lattices, Ti-6Al-4V auxetic the energy absorption capacity of the FCCR-IPC, as the
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metamaterials, Ti-6Al-4V Split-P TPMS lattices, structure transitioned to a less stable failure sequence. The
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Ti-6Al-4V double arrow-headed lattices, IPCs (VeroPlus FCCH-IPC initially exhibited a mixed shear band pattern,
+ TangoPlus), polymer circular-cell lattices, and polymer incorporating features of both inclined and vertical
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bio-inspired hierarchical lattices. The IPC metamaterials shear bands. Thereafter, the FCCH-IPC exhibited a more
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occupy a position in the upper-right corner of the Ashby pronounced positive Poisson’s ratio effect, characterized
plot, signifying their superior compressive strength by drum-like bulging deformation at the center of the
and SEA capabilities. This positioning underscores the structure. Throughout the compression, the FCCH-
exceptional performance of IPC metamaterials compared IPC exhibited relatively weak localized fracture regions,
to most existing metal and polymer-based lattice materials. eventually leading to a localized collapse.
The results demonstrate that the integration of rigid metals Overall, the fracture behavior of all IPC configurations
and ductile resins in the IPC design unlocks the potential is strongly influenced by the presence of the ductile
of lattice metamaterials, offering a promising pathway for epoxy resin matrix, which mitigates crack propagation
developing high-performance structural metamaterials. by redistributing stress. This characteristic ensures that
the IPC metamaterials undergo progressive collapse
3.2. Deformation sequences rather than abrupt failure, thereby improving their
Figure 3 depicts the deformation sequence of IPC structural integrity and energy dissipation. Furthermore,
metamaterials captured during quasi-static compression variations in deformation and failure behavior among the
experiment. The overall deformation process of IPCs can IPC configurations significantly affect their mechanical
be categorized into four distinct stages: strut buckling, performance. Although the FCCR-IPC achieved the
microcrack formation, localized failure zones, and highest compressive strength due to its vertical rib-
complete collapse. These stages reflect the progressive reinforced design, its brittler failure mode and prominent
failure mechanisms of IPC metamaterials, which are vertical fracture bands constrained its enhancement in
fundamentally different from the catastrophic collapse SEA, as evidenced in Figure 2D-F. In contrast, FCC-IPC
behavior of their corresponding truss microlattices. In the and FCCH-IPC achieved greater percentage increases in
initial stage, all three IPC configurations (FCC, FCCR, SEA compared to their corresponding truss microlattices,
and FCCH-IPCs) exhibited expansion deformation attributed to stricter crack propagation constraints within
concentrated at the bottom of the metamaterials, indicating their structures.
a pronounced positive Poisson’s ratio effect. This behavior
is attributed to the local buckling of truss unit cells, which 3.3. Strengthening-toughening mechanisms
is further influenced by the interactions between adjacent In the next section of the experiment, we further
unit cells. The positive Poisson’s ratio effect was particularly explored the performance advantages and strengthening-
evident in the early stages of deformation, as the ductile toughening mechanisms of the proposed IPC

Volume 1 Issue 1 (2025) 6 doi: 10.36922/esam.8554