Abstract:
Mixed-mode fracture characterization has been carried out considering the influence of
bimodulus elasticity and functionally graded material behavior of laminated composites
containing interface delamination. The formulation takes into account the thermoelastic
anisotropy arising out of curing stresses developed during the manufacturing stages. The
stress dependent elasticity problem has been solved numerically using iterative three
dimensional finite element procedures with Strain Energy Release Rate (SERR) as the
standard fracture parameter. Individual modes of SERR have been evaluated along the
delamination front based on the concepts of Modified Crack Closure Integral (MCCI). The
interface fracture behavior has been investigated for different numerical specimens
depicting Tee Joints and Skin-stiffener models with tension compression bimodulus ratio
R varying from 1 to 5 along the bond line with a linear functional profile for the respective
functionally graded bimodular specimens. Functionally graded bimodular adhesively
bonded tee joint reveals significant reduction in damage growth driving forces compared to
that of unimodular adhesive. The relative influence of residual thermal stresses have been
found to be more pronounced for bimodularity in comparison to functionally graded
properties for assessing the delamination damage progression characteristics in functionally
graded bimodular skin-stiffener specimens. The observations might assist the desirable
intention of the skin stiffener designer to retard the interfacial failure propagation rate in
order to intensify the structural integrity of the stiffened panel, so that the strength, lifetime
and reliability of the panel structure can be significantly upgraded.
Keywords: Bimodularity, Functionally graded, Interface delamination, Stress dependent
elasticity, Mixed-mode fracture, Strain energy release rate, Thermo-elastic anisotropy
