Kavli Affiliate: Chiara Daraio
| First 5 Authors: Chelsea Fox, Tommaso Magrini, Chiara Daraio, ,
| Summary:
The mechanical behavior of composite materials is significantly influenced by
their structure and constituent materials. One emerging class of composite
materials is irregular network reinforced composites (NRC’s), whose reinforcing
phase is generated by a stochastic algorithm. Although design of the
reinforcing phase network offers tailorable control over both the global
mechanical properties, like stiffness and strength, and the local properties,
like fracture nucleation and propagation, the fracture properties of irregular
NRC’s has not yet been fully characterized. This is because both the irregular
reinforcing structure and choice of matrix phase material significantly affect
the fracture response, often resulting in diffuse damage, associated with
multiple crack nucleation locations. Here, we propose irregular polymer NRC’s
whose matrix phase has a similar stiffness but half the strength of the
reinforcing phase, which allows the structure of the reinforcing phase to
control the fracture response, while still forming and maintaining a primary
crack. Across a range of network coordination numbers, we obtain J-integral and
R-curve measurements, and we determine that low coordination polymer NRC’s
primarily dissipate fracture energy through plastic zone formation, while high
coordination polymer NRC’s primarily dissipate energy through crack extension.
Finally, we determine that there are two critical length scales to characterize
and tailor the fracture response of the composites across the coordination
numbers: (i) the size of the plastic zone, and (ii) the size and geometry of
the structural features, defined as the areas enclosed by the reinforcing
network.
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