Modeling instrumented indentation testing to evaluate the behavior of PA11 and CaCO3 composites for offshore applications

PA/PCC micro-composites were prepared with different PCC contents. Compatibility tests were conducted with crude oil at aging times up to 28 days. The experimental phases of the instrumented indentation test (loading, creep and unloading) were modeled. Moreover, the heuristic method of differential evolution was used to fit the parameters. Loading curves showed higher scattering than the subsequent unloading, regardless of the aging time. The two unloading parameters exhibited quasi-linear dependency, but their dispersion was quite different. The mechanical and viscoelastic properties revealed that the PCC filler acted as a reinforcing agent. However, a higher PCC content did not lead to an increase in modulus, probably due to the poor interaction between particles and polymer. The hardness results showed that this property is not so sensitive to the material's morphology as are modulus data. All systems still had predominantly plastic behavior even after aging.