Mete Han Boztepe

Geometric discontinuities are unavoidable in additively manufactured polymer components and can significantly alter their mechanical response; however, their effects are rarely quantified in a systematic and geometry-comparative manner. In this study, the tensile behavior of FDM-printed PLA+ specimens with three different geometries—dog-bone, circular-hole, and U-notched (manufactured and tested in accordance with ASTM D638 (Type IV))—was experimentally and numerically investigated. Tensile tests were conducted using a universal testing machine equipped with an extensometer, while finite element simulations were performed using an experimentally calibrated Ramberg–Osgood-based elastic–plastic material model. The dog-bone specimens exhibited an ultimate tensile strength (UTS) of 41–43 MPa and a Young’s modulus of 3.06 GPa, representing the intrinsic material response under nearly homogeneous stress conditions. Circular-hole specimens maintained comparable strength (38–42 MPa) but showed reduced ductility (1.4–1.6%) and a slightly increased apparent modulus of 3.17 GPa due to localized deformation. In contrast, U-notched specimens displayed the highest apparent modulus (≈5.30 GPa) and nominal UTS (46–49 MPa), accompanied by a pronounced reduction in ductility (0.9–1.0%), indicating severe stress concentration and predominantly brittle fracture behavior. Finite element analysis showed excellent agreement with experimental results, with peak von Mises stresses reaching approximately 42 MPa for all geometries, corresponding closely to the experimentally measured tensile strength. These results demonstrate that geometric discontinuities strongly govern stress localization, apparent stiffness, and fracture initiation in FDM-printed PLA+ components. The validated Ramberg–Osgood-based modeling framework provides a reliable tool for predicting geometry-dependent mechanical behavior under quasi-static loading and supports geometry-aware design of additively manufactured polymer structures.

In this study, the mechanical properties of PLA+ samples produced through Fused Deposition Modeling (FDM) 3D printing are investigated. The research focuses on the effects of two critical parameters on tensile strength in 3D printers. These are raster angle and infill density. Raster angles of 0°, 90° and ±45° were chosen. The infill density, which determines the internal material distribution, was set to 20%, 50% and 100%. As a result of the tensile test, the highest ultimate strength value of 44.52 MPa was obtained in the ±45°-100% combination. The highest modulus of elasticity value was obtained from 90°-100% combination with 1.55 GPa. These findings highlight the critical role of printing parameters in determining the mechanical performance of FDM printed PLA+ parts. The study provides information for optimizing print settings to achieve desired strength and stiffness properties in 3D printed components for engineering applications.

In this study, the effects of raster angle and infill density on the flexural properties of PLA+ specimens fabricated by the Fused Deposition Modeling (FDM) process were investigated. A three-point bending test was conducted according to the ASTM D790 standard to evaluate the flexural strength and flexural modulus. Two different raster angles (0° and 90°) and three infill densities (20%, 50%, and 100%) were selected to examine the mechanical behavior of the samples under bending loads. The specimen with 100% infill density exhibited the highest flexural strength of 101.82 MPa, which was approximately 30% higher than those of the 20% and 50% infill specimens. This enhancement is attributed to the reduced porosity and improved interlayer bonding, which allowed for more effective stress transfer under bending conditions. The influence of raster angle became more pronounced at higher infill densities. The sample with a 0° raster angle demonstrated approximately 6.9% higher flexural strength and 14% higher flexural modulus compared to the 90° raster angle sample at 100% infill density.

In this study, the mechanical properties of PLA+ samples produced with different raster angles (0°, 90°, 0°/90°, 45° and ±45°) were investigated. Tensile tests were performed to determine the mechanical properties according to ASTM D-638 standard. The effects of raster angle on mechanical properties such as maximum force, elongation, toughness, modulus of elasticity, and ultimate tensile strength were analyzed. The results show that the raster angle significantly affects the mechanical behavior of PLA+ specimens. The highest maximum force and ultimate tensile strength were observed at 90°. In contrast, the lowest mechanical values were recorded at 0°, indicating a decrease in strength in this configuration. The ±45° raster angle exhibited the highest elongation and toughness, indicating greater ductility and energy absorption capacity. The modulus of elasticity showed relatively small differences between the different raster angles, with the highest value recorded at 90°. These findings highlight the critical role of raster angle selection in optimizing the mechanical performance of PLA+ components and provide valuable insights for additive manufacturing applications.

Non-Destructive Testing (NDT) methods are essential for assessing the integrity and reliability of composite materials without causing damage. Composite materials are widely used in industries such as aerospace, automotive, and civil engineering. Therefore, the demand for advanced inspection techniques has increased. This article provides an overview of various NDT methods, including Visual Testing (VT) and Visual Inspection (VI), ultrasonic testing (UT), infrared thermography (IRT), and acoustic emission (AE). The advantages, limitations, and applications of these techniques are discussed. Their role in detecting defects such as delaminations, porosity, and fiber breakage observed in composite structures is highlighted.