Through this report a methodology
for characterization of fracture related
parameters for numerical modelling of
delamination in composite materials is
developed. The methodology relies on
concepts of inverse parameter identification
and optimization techniques. The
numerical modelling is done through use
of the finite element method and cohesive
zone modelling.
An experiment is simulated in a parametric
finite element model and a residual is
defined as the discrepancy in some given
response from the numerical model and
the physical experiment. The parameter
identification is then done by minimization
of the residual.
The crack propagation is modelled using
user-defined interface elements through
ANSYS. A mixed mode multilinear cohesive
law for the user-defined interface element
is developed for this purpose. Since
the parameter identification is based on optimization
techniques, much time is spent
on formulating a proper objective function.
Initially, the objective function is based on
global structural response, but use of local
measurements in the fracture process zone
is also investigated.
The motivation for this method is to reduce
usual assumptions involved in characterization
of cohesive zone parameters,
increase the practical applicability by not
limiting the approach to coupon testing,
and gain as much information from few but
costly experiments.