Graphics Reference
In-Depth Information
if you mix a hard material with a soft material, in equal parts, you will get a
semi-soft, semi-hard material. It turns out that this is only partially correct.
The outcome of the resulting material depends on exactly
how
you mix the
materials.
For example, if you print hard and soft materials in a checkerboard pattern,
the result will be a new material that has certain strength. But if you print
the same two materials, still in equal parts but this time in a random pattern,
you get a much stronger material. The pattern, the way different materials are
blended together by the printer, matters.
If you squint and look down a checkerboard pattern, for example in
checkerboard loor tiling, you can see alternating black and white diago-
nals. Similarly, when two materials are printed in a checkerboard pattern,
the long diagonal chains of soft material become a “weak link,” which makes
the composite material weak. But when you print the two materials in a
random pattern, there is no such perfectly aligned weak link, so the overall
material is much stiffer.
Scientists have long known that the nanoscale arrangement of atoms in
a material matters to its macroscale properties. Practitioners igured out
centuries earlier that random patterns are stronger than regular patterns:
Blacksmiths quenched hot metal swords in cold water so that the metal
cooled quickly and formed small crystals with lots of random boundary
patterns, rather than annealing slowly into soft, smooth, malleable iron.
But for the irst time, we can
control
these patterns directly, explicitly. Not
yet at the atomic nanoscale level, but at the microscale, gradually inching
our way down.
Material properties can get even stranger. If you print multiple materials
in certain patterns, their material properties can go outside the range of the
base materials. You can mix weak and strong materials in a certain pattern
and get a new composite material that is even tougher than either one of the
original materials. It's a bit like getting steel-like material by mixing wood
and plastic, both weaker than steel.
One of the things that makes a material weak is that small imperfections
can turn into tiny cracks that then grow and propagate through the structure
