Effects of Stress Concentrations due to Bead Geometry in Large Format Polymer Additive Manufacturing.
2022-01-0398
03/29/2022
- Content
- Advancements in polymer Additive Manufacturing (AM) have led to growing adoption for structural applications in the aerospace, defense, and automotive industries. Nevertheless, extrusion-deposition type polymer additive manufacturing produces bead-shaped surface artifacts which create local stress concentrations that reduce the load carrying ability of the manufactured part. It is important to understand and characterize the effects of these surface artifacts, particularly in large format applications, where the larger layer heights and highly filled materials can exacerbate the sensitivity to stress concentrations. In this work, tensile test coupons were cut from the side panels of additively manufactured boxes, and tested to failure under uniaxial loading in the Z-direction. The parts were printed with a conductive, nano-filled PEKK material to represent high-strength and high-temperature applications. The test coupons were divided into two sets, with one set having the bead artifacts machined off to leave a smooth surface. This represents the control sample set without the effect of bead geometry. The machining was performed using a tabletop rotary disc polishing machining with fine-grit sandpaper in order to minimize any machining induced stresses. The other set was left intact in the “as-printed” condition. In addition, the entire process was repeated for four different sets of prints with different process parameters. The tensile test results showed that the smoothened specimens had an average ultimate tensile strength 40% higher that that of the “as-printed” specimens, thus highlighting the need to characterize the surface artifacts in extrusion-based polymer additive manufacturing.
- Citation
- Kundurthi, S., "Effects of Stress Concentrations due to Bead Geometry in Large Format Polymer Additive Manufacturing.," SAE Technical Paper 2022-01-0398, 2022, .