Static Response and Failure Analysis of Anisotropic Parts Printed using Fused Filament Fabrication

Abstract

Additively manufactured polymer parts produced via Fused Filament Fabrication (FFF) exhibit direction-dependent behavior as a result of the deposition process. This anisotropy presents a challenge for aerospace applications, where material properties and failure mechanisms vary depending on the orientation of the material. To accurately model and anticipate the behavior of Poly-Ether-Ether-Ketone (PEEK), a high-strength and high-temperature thermoplastic, this study explored strain limit failure mechanics. Uniaxial tension tests were performed on custom-dimensioned PEEK dogbone coupons across multiple material orientations and print rasters. Digital Image Correlation enabled full-field strain measurement across coupon surfaces and a "Strain Tornado" method was developed to interpret locally oriented strains. This analysis revealed the orientation-dependent strain limits and failure trends both between different material orientations and between FFF print rasters. A MATLAB Finite Element program was developed, incorporating transverse isotropy to predict anisotropic material behavior. Beam case studies explored this strain-based approach for flexural loading. These results establish the foundation for reliable strain-based design methods, building design confidence of 3D-printed PEEK in aerospace applications.