PSI - Issue 68

Estera Vălean et al. / Procedia Structural Integrity 68 (2025) 955 – 961 Vălean et al./ Structural Integrity Procedia 00 (2025) 000–000

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1. Introduction In general, thermoplastic materials have always attracted the attention of manufacturers due to their unique characteristics such as ease of processing, light weight, long life, and often ductility, Lebedev et al. (2018). However, compared to other materials, such as metals and ceramics, polymeric materials offer much less modulus and strength, due to which their use in various industries is limited, Singh et al. (2020). Nowadays, the most well-known method of building plastic parts is Additive Manufacturing (AM). Fused Deposition Modelling (FDM) is the most accessible additive technology, because it combines the low cost and simplicity of the machine with the low cost and availability of the thermoplastic polymers. In FDM, a thermoplastic filament is melted through a printer’s extrusion die and deposited sequentially, line by line and layer by layer, onto a heated printing plate. Creating a printed structure involves designing the model digitally using 3D design software and then printing it until the entire model is reproduced García Plaza et al. (2019) and Foltuț et al (2023). Currently, there are many different materials available on the market for FDM 3D printing including: ABS, PETG, TPU, Nylon, PLA (poly-lactic acid), and others. PLA is one of the most investigated materials in AM scientific research due to its excellent processability, biocompatibility and biodegradability, Penumakala et al. (2020).To enhance the performance of virgin PLA, researchers have explored the development of PLA-polymer matrix reinforced composites by incorporating various additive materials, including natural or synthetic fibers, metals, and ceramics, Rajpurohit et al. (2018). These efforts aim to improve the mechanical properties and broaden the application range of PLA. Vălean C. et al. (2024) studied the effect of reinforcing PLA with carbon fibers, glass fiber and bronze particles, in tensile and bending tests. They concluded that the mechanical behavior is strongly influenced by the type of filler in the matrix. The most ductile behavior was shown by pure PLA samples, and the most brittle by PLA reinforced with carbon fibers. Other researchers have studied how elasticity, density or tensile strength change, when natural powders such as: eggshell, walnut shell, marble powder, Cali et al. (2020) and Lohar et al. (2023) or hemp Lohar et al. (2022) are added to the virgin PLA. It was concluded that hemp improves the stiffness of the virgin material, while the other powders have a special impact on the properties mentioned above, but also on the elongation at break or the hardness of the new material. Also, many researchers have studied the dynamic Ji et al. (2024), compressive Ajay Kumar et al. (2020), tensile, fatigue properties Vălean E. et al. (2023) or even the effect of the notch opening angle Vălean E. et al. (2024) for this biodegradable material reinforced with various short or continuous fibers. The aim of the present work is to evaluate the effect of notches on static and dynamic bending properties of 3D printed PLA and PLA reinforced with short carbon fiber (PLA-CF).

Nomenclature AM

Additive Manufacturing Fused Deposition Modelling

FDM

3D

three-dimensional poly-lactic acid

PLA

PLA-CF

poly-lactic acid reinforced with short carbon fiber

PLA/PLA-CF-notch

sample of PLA/PLA-CF with notch

1. Materials and methods The materials used in this study are commercially available filaments of pure PLA (Silver - Prusa Polymers) and PLA mixed with short carbon fibre (Sunlu - containing short CF (<20%)). The 3D printing was conducted on Prusa MK3 printer using the following parameters: extruder temperature – 215 °C, build plate temperature – 60 °C, layer height – 0.2 mm, infill density – 100%, infill pattern – rectilinear, nozzle diameter – 0.4 mm, printing velocity – 80 mm/s and orientation position of the part on the built platform – 0°.