Abstract :
This study investigates the influences of
off-axis loading and of margin geometry on “margins
failure” observed in loaded curved bi-layer structures,
away from the contact loading point. Specimens of
hemispherical bi-layer model consist of glass shells
with varying margins geometry, and filled with epoxy
resin substrate are prepared. These specimens are
loaded with compliant PTFE Teflon cylindrical indenters,
with a modulus of several orders of magnitude
lower than the indented materials. Load is applied normally;
axisymmetric to the dome apex, and at 45◦ from
the axis of symmetry. In this fashion, the effect of offaxis
loading and the influence of margin geometry on
“margins failure” are studied. The onset of fracture is
observed in situ using a video camera system. Finite
element analysis is applied to determine basic stress
distribution within the dome structures, and to confirm
a shift in maximum tensile stress from the near-contact
area to the dome sides with the use of more compliant
indenters. Critical loads to initiate radial cracks and
damage evolution are presented, and interpreted with
the results of FEA.
