Using
molecular dynamics simulations of two generic glassy polymers,
we distinguish factors promoting cavitation that is followed by unrestrained
void growth and coalescence (i.e. by crazing and brittle fracture)
from “ductile” cavitation that does not lead to massive
void growth. Strain-controlled deformation in a wide range of wide
Poisson ratios ν reveals several features not apparent from
the uniaxial-deformation or uniaxial-stress protocols employed by
the vast majority of previous studies. In particular, for 0.125 ≲
ν ≲ 0.45, semiflexible, tightly entangled chains have
a significantly lower void volume fraction (but far more voids) at
the same strain and volumetric expansion ratio than their flexible,
loosely entangled counterparts. Voids in loosely entangled glasses
coalesce more often and grow faster, whereas voids in tightly (but
not loosely) entangled glasses continue to nucleate well into the
strain-hardening regime.