Polymeric material selection in desing

Applying short-term test results to polymer-based materials in design have some problems in terms of use as design data. Since the mechanical behavior of polymer-based materials changes depending on time and temperature, long-term test results must be used as design data. The safest way to do this in practical design calculations is to use creep test results. In this study, tensile creep tests were performed at room temperature with isotactic polypropylene (PP) samples at constant load and transition points from linear to nonlinear behavior were obtained with isochrono curves. It was shown that the transition from linear to nonlinear occurred for values between 40 and 50% of the maximum stress level. The decrease in the initial creep compliance level is inversely proportional to the increase in the strain level. In these calculations, the parameter that changes with time was taken into account in the operational life of the part made of polymeric material and the strains at the highest permissible strain level. A literature study on the selection of polymeric materials in design was presented and a comparison was made for the selected material as a result of the calculations made with both the Asbhy method and pseudo elastic design methods. Keywords: Mechenical Design, Material Selection, Polypropylene, Creep, Isochrono Curve, Isometric Curve