Design of Coupons and Test Methodology for Orthotropic Characterization of FFF-Processed Ultem 9085

• Published in: Structural Integrity of Additive Manufactured Materials and Parts pp. 176 - 187
• Main Authors: Hyatt, Tommy, Martin, Richard, Fields, Rich
• Format: Book Chapter
• Language: English
• Published: 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959 ASTM International 01.09.2020
• Subjects: B-Basis; Characterization; Coupon Design; Fdm; Fff; Manufacturing Engineering; Materials & Manufacturing Processes; Orthotropy; Pei; Ultem
• ISBN: 9780803177086; 0803177089
• DOI: 10.1520/STP163120190126

The increasing prevalence of additive manufacturing (AM) methods such as fused filament fabrication (FFF) is motivating the need to reliably predict mechanical behavior of additively manufactured parts. However, predicting mechanical behavior is highly dependent on the availability of accurate property data. Recently published material property data for polyetherimide (PEI, or Ultem) provides a significant step toward quantifying AM process repeatability, but mechanical properties reported are specific to the geometry of the coupons and are therefore less useful for structural analysis of other geometries. In order to quantify material properties in a way that is generically applicable and scalable to any geometry within a finite element model, mechanical testing needs to account for the orthotropy inherent to the additive manufacturing process. Additionally, edge effects and differing extrusion directions that typically exist between the perimeter contour passes and the interior fill passes for each printed layer need to be considered and accounted for. Current industry best practices for coupon fabrication for tensile, compression, and shear were evaluated, tested, and iteratively modified to determine the most effective coupon design and test configurations for capturing the orthotropic properties of FFF-processed Ultem 9085. Using the improved coupon design and test methodologies, three sets of coupons were fabricated and tested for tensile, compression, and shear in X, Y, and Z directions—both for pure contour construction and also for pure raster construction. Mechanical property results demonstrate typical properties that are meaningfully different than currently published data. Typical property results are presented. Using orthotropic design allowables in finite element models will allow analysts to predict mechanical behavior of arbitrary AM geometry.