• Composite materials
• elastic couplings
• experimental testing
• fiber reinforced polymers
• numerical modelling

This PhD thesis is devoted to investigation of any possible influence that elastic couplings have
on delamination phenomenon in continuous-fiber reinforced polymer (FRP) laminates. Results
presented in the dissertation have been published in journals from the Journal Citation Reports
(JCR) list as a series of five articles that are thematically related. The papers give an overview of
the effects elastic couplings have on both initiation and propagation phenomena of delamination
processes in laminates subjected to different fracture schemes in macroscopic sense, as well as on
the applicability of standardized test methods to determination of the critical strain energy release
rates (c-SERRs). In particular, the first article presented experimental research conducted on
glass/epoxy composite laminates subjected to the double cantilever beam (DCB) tests. In the
second article the effect of stiffness matrices terms on behavior of laminates subjected to the
mode I fracture scheme were described, as well as the real delamination front shapes were
investigated through fractographic analysis. The third article presented experimental
determination of fracture toughness for carbon/epoxy laminates with different delamination
interfaces and specific stacking sequences - exhibiting the bending-twisting (BT) and the
bending-extension (BE) elastic couplings, subjected to the DCB tests with respect to the ASTM
D5528 Standard. The experiments on delamination resistance were additionally monitored with
the acoustic emission (AE) equipment. After the stand tests, fractographic observations in
microscale by using the scanning-electron microscope (SEM) were performed. In the fourth
article, which is an individual work of the PhD Candidate, experimental research on influence of
elastic coupling phenomena on delamination in carbon/epoxy laminates subjected to the mode II
end-notched flexure (ENF) tests were presented. The respective experiments followed the ASTM
D7905 Standard; they were supported by acoustic emission, as well. Similarly, delamination
surfaces after the ENF tests were analyzed using the SEM . The fifth article describes numerical
analysis of the effect elastic couplings have on the strain energy release rate (SERR) distributions
along delamination front at the very moment of crack initiation for laminates subjected to the
mode III fracture scheme – in a macroscopic sense, by using the split cantilever beam (SCB)
configuration. Numerical simulations were conducted in the Abaqus/CAE finite element software
environment by using the virtual crack closure technique (VCCT) at different boundary
conditions (BCs) attributed to the laminate beam model. Additional analysis performed for hybrid
– glass/epoxy-carbon/epoxy laminates turned out to be advantageous from the point of view of limiting undesirable effects of elastic couplings. Application of hybrid configurations to coupled
laminates is being developed and examined as an object of prospective research.