Numerical-experimental method for the identification of plastic properties of polymers from microhardness tests

12 pags., 16 figs., 4 tabs.A computational method in conjunction with indentation measurements is presented to determine the yield stress and the tangential modulus of different polymeric materials. A novel approach is developed to select representative points at which finite element calculations are performed. Yield stress and tangential modulus can be obtained by minimizing the deviation between the calculated and the experimental data. Hardness values are also derived using finite element calculations and compared to those obtained from the fitting to the loading curve of depth-sensing experiments. © 1998 Elsevier Science B.V. All rights reserved.The method of identification of properties of polymers from microhardness tests was developed during the visit of the first author to the Institute of Structure of Matter, Madrid, sponsored by the TEM- PUS project JEP 06154-94. The authors are pleased to acknowledge the financial support by the DAAD, Bonn, Germany (Grant A/95/ 13482) and by the Latvian Council of Science (Grant 96.0504). Thanks are also due to DGICYT, Spain (Grant PB94-0049) for the generous support of this investigatio

Study of elastic properties of polymers from microhardness tests

18 pags., 6 figs., 2 tabs.A numerical method of identification to derive the elastic properties of polymers from indentation experiments has been developed. Five different polymers were tested: amorphous and semi-crystalline polyethylene terephthalate (PET), semi-crystalline polyvinylidene fluoride (PVF2), a copolymer of polyvinylidene fluoride and trifluorethylene, P(VF2/F3E) 60/40, and high pressure crystallised polyethylene (PE). The elastic properties of the polymers are calculated by two methods. On the basis of finite element solution, a simple function relating the load to the indentation depth and elastic modulus is first obtained. The elastic properties are then derived from the load-indentation depth and elastic modulus is first obtained. The elastic properties are then derived from the load indentation depth experimental data (loading curve). A second method to determine the elastic properties is based on using the experimental data of the unloading curve. Elastic properties obtained from loading and unloading curves are in good agreement.The method of identification of elastic properties of polymers from microhardness tests was developed during the visit of the first author to the Institute of Structure of Matter, Madrid, sponsored by the TEMPUS project JEP 06154-94. The authors would like to thank the project co-ordinator Prof. Dr.-Ing. A.K. Bledzki (University of Kassel) for the opportunity to perform the present study successfully. Thanks are also due to DGICYT, Spain (Grant PB94-0049) for their generous support of this investigation