چكيده به لاتين
The diversity in polymer properties enables the design and production of components with a wide range of applications that can operate under various environmental conditions. In recent years, additive manufacturing has emerged as an advanced production technology and has been widely used in various industries for the fabrication of polymeric parts. Since these parts are exposed to different environmental conditions, accurate evaluation of their mechanical properties and fracture behavior, especially at low temperatures, is essential to ensure their performance and safety. In this study, the mechanical properties and fracture behavior of specimens manufactured using the fused deposition modeling (FDM) process were investigated at ambient temperature. To analyze fracture behavior in pre-cracked ABS and PLA specimens, four crack angles 0°, 15°, 30°, and 40° were selected to induce Mode I, Mode II, and mixed-mode (I/II) loading. In addition, to study the effect of low temperatures on notched samples, U-notched ABS specimens with notch radii of 1, 2, and 4 mm were fabricated and tested under different temperature conditions. Four temperatures (25°C, 0°C, –10°C, and –20°C) were selected for thermal conditioning. After fabrication, all specimens were conditioned at their respective temperatures for 12 hours to ensure complete thermal exposure. The fracture load of both pre-cracked and notched specimens was experimentally measured using a three-point bending test. The results showed that for specimens with a fixed crack angle, the fracture load increased as the temperature decreased from 25°C to –10°C, and then dropped at –20°C. For PLA, the maximum difference in fracture load between 25°C and –10°C occurred at a 30° crack angle, with an increase of 29%. For ABS, the greatest increase (45%) occurred at a 0° crack angle. Furthermore, fracture loads at various temperatures were numerically predicted using the EMC-ASED and EMC-MS fracture criteria and compared with the experimental results. To gain a deeper understanding of fracture mechanisms, scanning electron microscopy (SEM) was used to examine the fracture surfaces of the cracked specimens. SEM images revealed that inter-strand voids and bonding strength decreased at –20°C compared to –10°C, which led to a reduction in mechanical performance and fracture resistance.
