Characterization of Material Stiffness on Injection Moulded Microspecimens Using Different Test Methods

Abstract

Injection moulding of polymer microparts can result in modified material behaviour due to process-induced changes in the internal properties. Thus, a transfer of the mechanical material properties in microparts, determined and valid on standardized test specimens, is only partially possible and should be verified on microtest specimens. This paper investigates both tensile and bending test methods for a suitable characterization of material stiffness in polymer microparts. For this purpose a down-scaled standard specimen is used and tested with different testing methods. The investigations reveal that the different testing methods result in comparable mechanical values. The effects of process-induced modified mechanical behaviour are observable in the investigated testing methods. Consequently, a microbending test is potentially a suitable method for characterizing material stiffness using microspecimens.

Biobased Dyes as Conductive Additives to Reduce the Diameter of Polylactic Acid Fibers during Melt Electrospinning

“…Although individual crystals could not be observed by POM, very little to no birefringence was detected in the melt-electrospun fibers and PFs, whereas birefringence was observed in the DFs because the degree of crystallinity was increased by drawing. The same technique was previously used to show that the degree of crystallinity in PA66 tensile bars was dependent on the mold temperature [51]. Our combined DSC and POM data, therefore, indicate that the PLA fibers produced by melt electrospinning are similar to PFs produced by melt spinning, which have a much lower T cc value than DFs.…”

Competition between Heterogeneous Nucleation and Flow‐Induced Crystallization of Polyamide 66 and Its Carbon Nanotube Composites

“…These material properties are driven by the polymer DOI: 10.1002/marc.202200418 microstructure. [4][5][6] In practical application, polymer engineers can use crystallization data to tune a specific polymorph and microstructure in a solidified part to obtain optimal part properties.…”

An adaptable flexural test fixture for miniaturised polymer specimens

“…Such quantities are not sufficient for conventional protocols and standards to determine bulk properties. This means that the typical standard sample size as recommended by British Standard (EN ISO 178:2019) with dimensions of 80 � 10 � 4 mm 3 [1] for conventional mechanical testing cannot be produced, and non-conventional test equipment is required to perform miniaturised mechanical tests.…”

“…Constraints of tensile and flexural microtesters and of mechanical analysers (e.g. dynamic and thermomechanical) include the requirements for specific specimen shapes, significant specimen gripping challenges, limited force and displacement range, and the need for specialised equipment accessories to test in different environmental conditions [2,3]. The literature summarised in Table 1 reports examples of different approaches to develop test fixtures and methods for simple geometries of miniature specimens of polymeric materials to investigate mechanical behaviour, using specimens with characteristic dimensions of �15 mm.…”