Journal of polymer engineering vol:21 issue:2-3 pages:111-118
In order to design and dimension micro parts it is important to know the exact material properties. Properties valid for common polymer parts cannot be applied to micro parts. To study this, tensile test bars of the materials polyoxymethylene (POM), polystyrene (PS) and polypropylene (PP) of different sizes were examined. Both increasing and decreasing yield stress was measured. A size reduction of the cross-section from 40 mm(2) to 1 mm(2) reveals a dependency of the results on the type of material. POM shows a reduced yield stress of about 10%, whereas PP and PS show an increased yield stress of about 20% and 40%, respectively. A further size reduction to 0.025 mm(2) shows a decrease in yield stress of about 20% for POM. The results of this study indicate that mechanical properties valid for common specimen sizes cannot be applied to micro parts.