Nanoindentation of solvent-cast and compression-moulded poly(lactic-co-glycolic acid) to determine elastic modulus and hardness

Nano- and micro-mechanical properties of solvent-cast and compression-moulded poly(lactic-co-glycolic acid) materials were investigated. Nanoindentation experiments were performed at different indentation depths and used to investigate the elastic modulus, hardness, contact stiffness, plasticity index and indentation pile-up behaviour of the material for a range of loading and unloading rates. The solvent-cast material was more elastically compliant and plastically softer than the compression-moulded material, and it also displayed lower work hardening characteristics. Loading rate dependence was found to be relatively insignificant. The measured elastic modulus and hardness were strongly depth dependent for both forms of the material, for indentations less than 3000 nm. The results allowed recommendations to be made on the choice of test protocol parameters for reliable nanoindentation testing of this material.