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Reliability of thin hard films on compliant substrates is a key factor governing theuse of emerging flexible substrate devices where compressive stresses can lead todelamination and buckling. Previous modeling of buckle-driven delamination inhard film-compliant substrate systems has shown the importance of elasticmismatch on fracture morphologies and measured fracture energies. This studyhighlights the contributions of plastic deformation during fracture between rigidfilms and relatively compliant substrates. Depositing 100 nm and 200 nm thickW films onto silicon and PMMA substrates that spanned two orders of magnitudein stiffness triggered Euler and telephone cord buckles that varied markedly inmorphology with substrate compliance. For films on PMMA, buckling wasaccompanied by significant substrate deformation and yielding. In this paper weshow how substrate compliance, deformation, and yielding affect buckleformation, susceptibility to interfacial fracture, and fracture energies in hardelastic films on compliant substrates.