Influence of manufacturing conditions on measurement of mechanical material properties on thermoplastic micro tensile bars

Injection moulding of thermoplastic micro parts result in modified material behaviour due to process induced changes of the internal properties. Thus, a transfer of the mechanical material properties, determined and valid on standardized test specimens, to micro parts is only possible to a restricted extent. Tensile bars with scaled dimensions are used to investigate the influence of part size with injection moulded specimens (with size depending process conditions) and milled specimens (without size depending process conditions). Milled scaled tensile bars provide comparable and reproducible mechanical material properties due to their identical morphological structure. Injection moulded scaled tensile bars have a size dependent morphology which can lead to modified mechanical properties. It is shown that the mechanical properties of thermoplastic polymers react differently with reduced dimensions, especially due to the crystallisation behaviour.