The aim of this thesis is to study the strain rate effects through materials response from indentation test. Polymeric solid material, especially Polycarbonate (PC), Polymethyl methacrylate (PMMA), High Density Polyethylene (HDPE) and Polyamide Nylon 6.6 -30% glass fiber reinforced (PA 6.6-30% GFR), were selected as study materials due to their high strain rate sensitivity even at room temperature. The first two parts of this work were focused on the study of the thermomechanical behavior of polymer materials. Bibliographical studies of thermoplastic polymer materials, amorphous and semi-crystalline, was established in order to understand their microstructure and deformation mechanism. Moreover, compression tests were performed on study materials with several crosshead speeds values then the results was exploited analytically. The last three parts were focused on mechanical characterization using Instrumented Indentation Test (IIT). Firstly, numerical simulation of a conical indentation test ( =70.3°) with a constant rate displacement ( = 1 µm/s) was established using the identified G’sell behavior parameters and the power-law parameters from compression test. Parameter identification using Inverse Analysis from numerical material shows the non-uniqueness of G’sell parameters which gives the same indentation curve. Thus, theoretical study of conical indentation test was established considering power-law model. A new concept of the representative strain and the representative strain rate, based on solution domain which associate the set of parameters leading to the same indentation curves, was proposed. Very satisfactory results was obtained when identification process using this average representative strain rate is applied to a numerical material define by a power-law model. However, this method could not show its efficiency because the mechanical behavior of the real material is not correctly modeling with a power-law at a wide range of strain and strain rate. Finally, the new concept of the representative strain and the representative strain rate proposed on this work contributes to a new investigation tools to exploit the results form IIT and provide a very interesting perspectives.
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