This Standard will provide a reliable and repeatable test method to measure the shear strength and modulus of polymer AM parts additively manufactured using an extrusion-based process, and will be particularly useful in measuring the shear properties of the inter-layer weld formed when parts are manufactured using these processes. This inter-layer weld is known to be the weakest area of polymer parts made by extrusion AM. The new Standard will provide partial fulfilment of AMSC Roadmap Gaps FMP1 “Material Properties” and FMP4 “Design Allowables”. Other shear test Standards, e.g. D3846, can interrogate inter-layer weld strength but suffer from specimen manufacturing challenges (tolerances), and inaccuracies due to test fixture interference. Also, D3846 does not allow for direct measurement of gage section displacement, and therefore determination of modulus, whereas the new Standard will address all of these problems. Other test methods have been used to try to measure inter-layer weld properties, e.g. D638 for tensile properties, but results typically suffer from high variability and significant numbers of inappropriate failure modes. The large number of tests done to date with the new proposed test method have shown excellent repeatability and consistent good failure modes. Data generated from this new Test Standard will be of use to part designers, manufacturing process developers, and quality assurance personnel.
The title and scope are in draft form and are under development within this ASTM Committee.