Session: Government Agency Student Posters

Paper Number: 174011

Extended X-Ray Ct Imaging and Tensile Test Studies of 3d-Printed Composites: Linking Process-Structure-Property Relationship 

This study investigates the process–structure–property relationships in carbon fiber-reinforced polylactic acid (PLA) composites fabricated via fused filament fabrication (FFF), focusing on the combined effects of print orientation and specimen size. FFF is a widely used additive manufacturing method due to its low cost and design flexibility, but it often introduces microstructural defects such as voids, incomplete fusion between layers, and anisotropic material behavior. These defects, which are strongly influenced by printing parameters such as infill orientation and build direction, can significantly affect the mechanical performance of printed parts. As such, understanding how print process conditions relate to internal features and mechanical behavior is essential for optimizing 3D-printed composite structures for functional applications.

To explore these relationships, tensile specimens were printed at three distinct infill angle configurations,[0°,90°], [-45°,45°], and [30°,60°], based on ASTM D638 Type I and Type IV tensile geometries. These two specimen types differ in overall size and gauge dimensions, allowing for an investigation into geometry-dependent size effects. Each configuration was fabricated in both flat (XY plane) and on-edge (XZ plane) orientations. Multiple samples were printed for each case to enable a statistically meaningful comparison of both mechanical properties and microstructural variability.

To quantify internal defects and correlate them with performance, high-resolution X-ray micro-computed tomography (Micro-CT) was performed on 15 mm³ cubic samples printed using the same infill configurations. Scans were acquired at a 16 μm resolution, enabling detailed porosity measurements including total void volume fraction and spatial distribution. These metrics were used to characterize how infill orientation and print direction influence internal defect formation, with results indicating that [0°,90°] prints generally exhibited the lowest porosity levels across all configurations.

Uniaxial tensile tests were then performed on five samples per geometry and orientation using a universal testing machine. Key mechanical properties including Young’s modulus, ultimate tensile strength (UTS), and strain at failure were recorded. Type IV specimens consistently demonstrated greater ductility and lower modulus compared to Type I specimens, reflecting a geometry-driven size effect. Additionally, differences in failure modes were observed: Type I specimens failed abruptly with brittle fracture, while Type IV specimens showed progressive deformation before failure, suggesting more distributed stress and strain accumulation.

Results also indicate a clear inverse relationship between porosity content and UTS across print orientations. Samples printed at [0°,90°] not only had lower void fractions but also consistently achieved higher tensile strength, reinforcing the idea that void minimization is critical for enhancing structural performance. Notably, this study offers a novel comparison of two ASTM specimen geometries printed with identical settings, a factor rarely explored in existing literature, and highlights how geometry and scale influence both defect formation and mechanical behavior.

By integrating Micro-CT analysis with mechanical testing across a matrix of print orientations and specimen types, this work provides new insights into the process-induced variability of FFF composites. These findings can inform improved design and manufacturing strategies for fiber-reinforced printed components in engineering applications where strength and reliability are essential.

Presenting Author: Roman Linkugel Embry-Riddle Aeronautical University

Presenting Author Biography: Roman Linkugel is a senior in aerospace engineering at Embry-Riddle Aeronautical University and a member of the university's Honors Program. He conducts research in the Advanced Integrated Materials (AIM) group under Dr. Jun Li and Dr. Yizhou Jiang. His academic interests include additive manufacturing, composite materials, structural testing, flight testing, materials characterization, and aircraft design. After completing his undergraduate degree, he plans to pursue a career in the aerospace industry.

Authors:

Roman Linkugel Embry-Riddle Aeronautical University
Yizhou Jiang Embry-Riddle Aeronautical University
Jun Li Embry-Riddle Aeronautical University