  Symmetrically bonded thin and flexible T-peel specimens, when tested on
vertical travel machines, can be subject to significant gravitational loading;
with the associated asymmetry and mixed-mode failure during peeling. This can
cause erroneously high experimental peel forces to be recorded which leads to
uncertainty in estimating interfacial fracture toughness and failure mode. To
overcome these issues, a mechanical test fixture has been designed for use with
vertical test machines, that supports the unpeeled portion of the test specimen
and suppresses parasitic loads due to gravity from affecting the peel test. The
mechanism, driven by the test machine cross-head, moves at one-half of the
velocity of the cross-head such that the unpeeled portion always lies in the
plane of the instantaneous center of motion. Several specimens such as bonded
polymeric films, laminates, and commercial tapes were tested with and without
the fixture, and the importance of the proposed T-peel procedure has been
demonstrated.
