Abstract
A modeling method to extract the mechanical properties of ultra-thin films (10–100 nm thick) from experimental data generated by indentation of freestanding circular films using a spherical indenter is presented. The relationship between the mechanical properties of the film and experimental parameters including load, and deflection are discussed in the context of a constitutive material model, test variables, and analytical approaches. Elastic and plastic regimes are identified by comparison of finite element simulation and experimental data.
Highlights
Freestanding ultra-thin polymer films are utilized in a variety of applications, including sensors, catalysis, filtration, and tissue engineering[1,2,3,4]
We found, for our films, that the elastic assumption is valid only for small values of indentation depth
We argue that the closest approximation of the fit values to the real values lies at the point where the error metric begins to increase rapidly, around 0.15 mm indentation depth
Summary
Freestanding ultra-thin polymer films are utilized in a variety of applications, including sensors, catalysis, filtration, and tissue engineering[1,2,3,4]. The mechanical properties of ultra-thin films are known to change as the film dimensions approach the molecular size scales[8,9,10]. Measuring these properties has been difficult even for substrate-supported thin films, and there are only few measurements that have been attempted on freestanding films[11]. We present a method that can be used to extract mechanical data from such tests and construct full stress–strain curves for films of this
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