Ultralight Metallic/Composite Materials
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parenchyma, and sponge optimize superior mechanical properties at low density by
implementing a highly porous, complex architected cellular core [1]. The same engineering and architectural principles at the material scale have been used by humankind
to develop materials with higher mechanical efficiency and lower mass in many weightcritical applications. The emergence of advanced manufacturing technologies such as
additive manufacturing and three-dimensional (3D) laser lithography offer the opportunity to fabricate ultralight metallic and composite materials with intricate cellular architecture to location-specific requirements. For example, the world’s lightest metal [2, 3],
Fig. 1(a), and reversibly assembled ultralight carbon-fiber-reinforced composite materials [4], Fig. 1(b), with micro-architected cellular structures have been recently fabricated
at HRL Laboratories and MIT Media Lab-Center for Bits and Atoms, respectively.
(a)
(b)
Fig. 1. (a) Metallic cellular microarchitecture [2, 3] and (b) assembly of a cuboct carbon-fiberreinforced composite microlattice [4].
Architected cellular materials enable to include the effect of the structural hierarchy
in the determination of the bulk material properties [5]. For example, fiber-reinforced
cellular composites recently fabricated at MIT Media Lab-Center for Bits and Atoms
exhibit structure on more than one length scale [4], and metallic microlattice materials
recently fabricated at HRL Laboratories span three different length scales (nm, µm, mm)
[2, 3]. Cheung and Gershenfeld [4] fabricated a cubic lattice of vertex-connected octahedrons, called cuboct, consisting of solid bars with square cross section t × t and
length l. They examined only ultralight cellular composites with thickness-to-length
ratio, = t/l smaller than 0.1 and obtained stretch-dominated lattice-based composites.
To form volume-filling lattice structure, they [4] produced many small cross-shaped
building blocks assembled by mechanical interlocking connections. Each building block
constitutes four conjoined strut members to one locally central node where a shear clip
is inserted after the assemblage of all blocks. Strut members are composed of unidirectional fiber composite beams and looped fiber load-bearing holes [4]. Schaedler et al.
[2] and Torrents et al. [3] fabricated nickel-based micro-architected cellular materials
composed of hollow tube members with L = 1 to 4 mm node-to-node spacing, D = 100
21
parenchyma, and sponge optimize superior mechanical properties at low density by
implementing a highly porous, complex architected cellular core [1]. The same engineering and architectural principles at the material scale have been used by humankind
to develop materials with higher mechanical efficiency and lower mass in many weightcritical applications. The emergence of advanced manufacturing technologies such as
additive manufacturing and three-dimensional (3D) laser lithography offer the opportunity to fabricate ultralight metallic and composite materials with intricate cellular architecture to location-specific requirements. For example, the world’s lightest metal [2, 3],
Fig. 1(a), and reversibly assembled ultralight carbon-fiber-reinforced composite materials [4], Fig. 1(b), with micro-architected cellular structures have been recently fabricated
at HRL Laboratories and MIT Media Lab-Center for Bits and Atoms, respectively.
(a)
(b)
Fig. 1. (a) Metallic cellular microarchitecture [2, 3] and (b) assembly of a cuboct carbon-fiberreinforced composite microlattice [4].
Architected cellular materials enable to include the effect of the structural hierarchy
in the determination of the bulk material properties [5]. For example, fiber-reinforced
cellular composites recently fabricated at MIT Media Lab-Center for Bits and Atoms
exhibit structure on more than one length scale [4], and metallic microlattice materials
recently fabricated at HRL Laboratories span three different length scales (nm, µm, mm)
[2, 3]. Cheung and Gershenfeld [4] fabricated a cubic lattice of vertex-connected octahedrons, called cuboct, consisting of solid bars with square cross section t × t and
length l. They examined only ultralight cellular composites with thickness-to-length
ratio, = t/l smaller than 0.1 and obtained stretch-dominated lattice-based composites.
To form volume-filling lattice structure, they [4] produced many small cross-shaped
building blocks assembled by mechanical interlocking connections. Each building block
constitutes four conjoined strut members to one locally central node where a shear clip
is inserted after the assemblage of all blocks. Strut members are composed of unidirectional fiber composite beams and looped fiber load-bearing holes [4]. Schaedler et al.
[2] and Torrents et al. [3] fabricated nickel-based micro-architected cellular materials
composed of hollow tube members with L = 1 to 4 mm node-to-node spacing, D = 100