2026 Annual International Solid Freeform Fabrication Symposium (SFF Symp 2026): Printed Polymer Performance: Structure, Anisotropy, Interfaces, and Durability
Program Organizers: David Leigh, University of Texas at Austin
Tuesday 8:00 AM
August 4, 2026
Room: Zlotnick Ballroom 2
Location: AT&T Center
8:00 AM
Nondestructive Characterization of Hybrid Ironed FFF-Printed PLA Parts: Partha Pratim Pandit1; Harshith Kumar Adepu1; Davis Avera1; Rebecca Ang1; Luz Sotelo1; 1Purdue University
Ironing in 3D printing is primarily used to improve surface appearance and dimensional accuracy. However, most applications focus on ironing only the top or bottom layers, however, the potential benefits of applying ironing throughout the build process are still largely unexplored. To understand the effect of internal ironing on fused filament fabrication (FFF) printed PLA parts, three cylindrical specimens of 15 mm diameter, 10 mm height were printed with 0, 5, and 10 ironed layers, which corresponding to 0%, 10%, and 20% of total layers. Nondestructive evaluation techniques, including X-ray CT and ultrasonic evaluation, were employed to understand the effects of ironing on porosity and mechanical properties of these hybrid 3D printed polymers. Findings from this study demonstrates internal ironing can reduce porosity by eliminating smaller pores and breaking larger voids into smaller defects, although diminishing returns may occur with additional ironing.
8:20 AM
Quantifying Degree of Anisotropy in Polymer AM Parts: Davis Avera1; Partha Pandit1; Mark Yang1; 1Purdue University
Anisotropy plays a significant role in polymer additive manufacturing (AM). This affects performance and reliability of AM parts. Nevertheless, studies which investigative anisotropy often overlook the effects of interlayer dwell time (the time spent between deposited layers). Interlayer dwell time affects interlayer bonding, material properties, and the thermal history of the parts. This study aims to investigate how interlayer dwell time influences the degree of anisotropy in Fusion Filament Fabrication (FFF) AM PLA components. This is accomplished by using ultrasonic time-of-flight measurements to calculate the directional wave speeds and elastic moduli. Samples were fabricated using FFF with systemically varied dwell-time parameters, post-processed, and analyzed using ultrasonic immersion testing. The results show quantitative insight into how dwell time changes the anisotropic response of FFF parts, which is critical for load bearing components, process-aware design, and multi-part build planning and assembly.
8:40 AM
Transparent Additively Manufactured Parts for Improved Mechanical Properties: Justin Kim1; Rebecca Ang1; Davis Avera1; Harshith Adepu1; Partha Pandit1; Luz Sotelo1; 1Purdue University
While a very useful tool for rapid prototyping as well as to produce complex and custom parts, Additive Manufacturing (AM) via Fused Filament Fabrication (FFF) poses many challenges. Parts are often porous due to inconsistencies during the printing process and improper handling and storage of feedstock. Utilizing clear filaments allows defects such as porosity to become quickly evident by visual means. However, there is limited literature on whether clear printing can lead to improved material properties as defects are minimized for transparency. This study aims to determine whether an optically transparent FFF 3D-printed polyethylene terephthalate glycol (PETG) part is less anisotropic than a typical PETG part using nondestructive evaluation. The porosity was determined through X-Ray computed tomography (CT), and the stiffness was found from the P-wave modulus, which was derived from ultrasound measurements. This study highlights an alternative approach to optimizing parameters towards stronger, multipurpose FFF 3D-printed parts.
9:00 AM
Nondestructive Characterization of Heat and Print-Bonded Multi-Material FDM Interfaces: Harshith Kumar Adepu1; Partha Pandit1; Rebecca Anne Ang1; Luz Sotelo1; 1Purdue University
Multi-material fused deposition modeling (FDM) produces interfacial defects including voids and incomplete polymer diffusion, and these interfaces are typically characterized only through destructive mechanical testing. This study applies X-ray computed tomography (CT) and immersion ultrasound to nondestructively quantify interfacial porosity and geometric uniformity in ABS/HIPS cylindrical specimens. Specimens were fabricated by two bonding methods: direct print-bonding at three nozzle temperatures (240°C, 255°C, 270°C) and post-print heat bonding at 215°C. X-ray CT revealed that the heat-bonded sample exhibited substantially lower bulk porosity (0.39%) compared to print-bonded samples (1.39%-3.54%), with porosity increasing as nozzle temperature decreased. However, immersion ultrasound amplitude and time-of-flight C-scans revealed greater spatial variation across the heat-bonded interface, indicating reduced geometric uniformity relative to the printed samples. These results demonstrate a tradeoff between porosity reduction and interfacial uniformity, and highlight the necessity of combining multiple NDE modalities to fully characterize multi-material FDM bond quality.
9:20 AM
Quasi-Static and Dynamic Properties in Flexible Fused Filament Fabrication Polymers: Rebecca Anne Ang1; Partha Pandit1; Anna Keim1; Monique McClain1; Luz Sotelo1; 1Purdue University
Additively manufactured (AM) Fused filament fabrication (FFF) polymers exhibit varying properties depending on if the applied load is quasi-static or dynamic, due to the viscoelasticity of thermoplastic polymer chains. Although extensive research exists on FFF polymer material properties, much of it focuses on rigid polymers. This study investigates the hypothesis that the addition of carbon fiber filler significantly affects the quasi-static and dynamic viscoelastic properties of FFF AM thermoplastic polyurethane (TPU). This objective is accomplished by performing dynamic mechanical analysis (DMA), tensile, and ultrasound testing. Complex moduli of TPU and carbon fiber filled TPU (TPU-CF) were estimated using ultrasound and DMA to capture a broad dynamic loading range while verifying results across measurements. Tensile testing was done to measure the quasi-static modulus. These results are expected improve predictions of FFF AM TPU’s behavior, while this multimodality approach enables a more holistic understanding of the viscoelastic transition for flexible AM polymers.
9:40 AM Break
10:00 AM
AI-Assisted Process Optimization for Multi-Material Thermoplastic 3D Printing and Charpy Impact Analysis: Kazi Md Masum Billah1; Caleb Canon1; Josiah White1; Safikah Nidhi1; 1University of Houston Clear Lake
Multi-material thermoplastic structures were fabricated using fused filament fabrication by combining thermoplastic polyurethane (TPU) and polylactic acid (PLA) to investigate their impact behavior. In the printed specimens, TPU was embedded as the middle layer, while PLA formed the top and bottom layers to create a sandwich-like structure. The TPU volume fraction was varied from 10% to 50% to evaluate its influence on energy absorption and mechanical performance. Charpy impact testing was conducted to characterize the toughness and fracture behavior of the fabricated specimens. The study further explores the application of artificial intelligence (AI) techniques to analyze processing parameters and predict impact performance based on material composition. Results demonstrate that increasing TPU content enhances impact resistance and energy absorption capability, while maintaining structural rigidity through the PLA outer layers. This work highlights the potential of AI-assisted multi-material additive manufacturing for developing tailored lightweight structures with improved mechanical performance.
10:20 AM
Elastomeric Energy Absorbers Prepared from 3D Printed Sacrificial Molds: Derek Bischoff1; Michael DeGrange2; Eric Wetzel1; 1DEVCOM Army Research Laboratory; 2SURVICE Engineering
Additively manufactured (AM) polymer lattices are highly tailorable geometries used to achieve a tunable compressive mechanical response desirable in applications such as seat cushions, protective packaging, and helmet pads. They can be directly manufactured using vat photopolymerization and fused filament fabrication (FFF), however, their performance is limited by the mechanical properties (e.g., durometer, strain to break) of available printable elastomers. Additionally, integrating multiple elastomers into the same lattice can prove challenging. Herein, dissolvable polymer molds fabricated via FFF are used to resin cast energy absorbing structures from conventional elastomeric resins that are not generally amenable to direct 3D printing. Because the molds are dissolved after casting, complex and interpenetrating lattices can be formed. Furthermore, interpenetrating lattices comprising multiple elastomer material grades can be implemented. This study shows how dissolvable printed molds can be used to efficiently create complex functional shapes from materials that are not specifically formulated for 3D printing.
10:40 AM
Overcoming Z-Axis Anisotropy in FFF PEEK Components via Vacuum-Assisted Epoxy Infiltration: Francesco Tamburrino1; Beatrice Aruanno1; Alessandro Paoli1; Armando Razionale1; Sandro Barone1; 1University of Pisa, Department of Civil and Industrial Engineering
Additive manufacturing of PEEK by Fused Filament Fabrication (FFF) is limited by poor interlayer adhesion, porosity, and pronounced anisotropy in vertically printed components. This work presents a vacuum-assisted infiltration process using a low-viscosity, high-temperature epoxy resin as an efficient post-processing strategy. Evaluated under critical vertically printed conditions, digital microscopy confirms the resin effectively fills interconnected voids, promoting mechanical interlocking. Results show flexural strength increases up to 80% compared with as-printed and thermally annealed specimens, alongside improved strength-to-weight ratios and negligible material costs. Compared with conventional high-temperature thermal annealing, the proposed approach requires substantially lower processing temperatures (curing at 60°C) and shorter treatment times. This demonstrates the potential of targeted epoxy infiltration as a scalable, industrially viable post-processing route for high-performance lightweight FFF PEEK components.
11:00 AM
Spatial Heterogeneity of the Mechanical Properties in DLP 3D Printed Polymers: Kubra Sekmen1; Xuyang Chang2; Baris Telmen3; Simon Hallais4; Kostas Danas4; Andrei Constantinescu4; 1Virginia Tech; 2University of Science and Technology in Beijing; 3Institut des Sciences de la Mécanique et Applications Industrielles (IMSIA), ENSTA Paris, Institut Polytechnique de Paris; 4Laboratoire de Mécanique des Solides, CNRS, École Polytechnique, Institut Polytechnique de Paris
Digital light processing (DLP) is a widely used additive manufacturing technique that fabricates three-dimensional parts layer by layer through in-plane photopolymerization. However, heterogeneities in ultraviolet (UV) light exposure during printing can induce significant variations in the chemical, thermal, and mechanical properties of the printed material. The small thickness of each deposited layer leads to repeated UV exposure of previously printed layers along the build direction. In addition, within the printing plane, the UV light projected by digital micromirrors generates pixel-scale exposure heterogeneity. These effects result in nonuniform photopolymerization, heterogeneous material properties, and localized polymerization shrinkage, which together promote the formation of surface wrinkles. Such wrinkle patterns are associated with stress relaxation via buckling of a stiffer surface layer, resulting in out-of-plane deformation. This presentation discusses these mechanisms based on experimental observations from atomic force microscopy (AFM) and scanning electron microscopy (SEM), emphasizing wrinkles as precursors to cracks and dimensional inaccuracies.
11:20 AM
Chemical Degradation of an SLA 3D-Printed Photopolymer: Effects of Printing, Post-Processing, and Chemical Environments: Md Shahjahan Mahmud1; Yirong Lin1; Brian Schuster1; 1University of Texas El Paso
Stereolithography (SLA) 3D-printed photopolymers are promising candidates for demanding industrial and engineering applications where chemical durability is critical. However, systematic understanding of how printing and post-processing parameters govern baseline properties and subsequent chemical resistance remains poorly understood. This study investigates degradation behavior and mechanisms of an SLA-printed methacrylate-based polymer under varying print orientations, layer heights, and post-curing conditions, followed by accelerated aging in polar, non-polar, and strongly acidic media over 12 weeks. Higher post-curing temperatures maximized degree of conversion, significantly reducing chemical susceptibility. Among all environments tested, nitric acid induced the most severe deterioration, over 81% tensile strength loss, 94% modulus reduction, and 47% Tg depression, while non-polar solvents caused negligible degradation. FTIR, and mass spectrometry confirmed acid-catalyzed ester hydrolysis within methacrylate-urethane linkages as the dominant degradation pathway, while diffusion-controlled plasticization prevailed in polar media. These findings establish critical performance baselines for designing chemically durable additively manufactured photopolymer systems.