## 1 Introduction  
The production of structural elements can be achieved through various methods such as turning, casting, and milling. In recent years, additive manufacturing (AM) or three-dimensional (3D) printing has emerged as an alternative to these traditional methods. The choice of manufacturing technology depends on the type of pattern desired, the quantity being produced, time constraints, available resources, and other factors. If a high-quality pattern is required, particularly for industrial purposes, turning, casting, or milling is a probable choice. However, if a prototype or a small number of elements is needed, 3D printing may be a more suitable option. Another promising aspect of using AM lies in the reduction of material waste, the implementation of a lightweight design, high-strength truss geometries, and the opportunity of personalized customization and the creation of specific add-ons tailored to the requirements of the application [1]. Regardless of the manufacturing technology used, computer simulations can be used to calculate stresses and optimize the design. One area of research that needs to be constantly monitored is materials. The most used materials in 3D-printed constructions are polymer-based materials. The selection of materials for production depends on many factors and there are advantages and disadvantages to consider. One specific drawback of polymer materials is their sensitivity to damage caused by exposure to UV radiation and the general ageing of the material [2]. The ageing of polymer materials refers to the process of their properties changing over time under the influence of various external factors. Polymer materials are preferred due to their flexibility, durability, and cost-effectiveness. However, prolonged exposure to UV radiation, high temperatures, chemical substances, and mechanical loads can lead to the degradation of the polymer and changes in their properties [3]. The most used 3D printing techniques include vat photopolymerization, fused filament fabrication (FFF), direct ink writing (DIW), Inkjet printing or material Jetting, and polymer powder bed fusion [1]. Fused filament fabrication (FFF) or fused deposition modeling (FDM), considered one of the most promising additive manufacturing methods due to its versatility, reliability, and affordability, involves the direct deposition of a thermoplastic polymer filament in a layer-by-layer fashion [1; 4]. The most commonly used polymers in the FFF technique are acrylonitrile butadiene styrene (ABS) and polylactic acid (PLA) [4]. Using this technique, the material is selectively dispensed through a nozzle. With the increasing and widespread use of AM in various applications, increased demands are placed on the parameters of the construction process and the performance of the finished object. Overall, the shortcomings of AM can be seen as areas of opportunity and development [5]. One of them may be the increased demand for polymers used in AD itself. It is generally known that polymers, due to their good mechanical properties, are a very desirable material for the construction of various products. On the other hand, they represent a serious environmental problem due to their inability to biodegrade. Therefore, in today's context, there is an increasing consideration of the possibility of using biodegradable polymers and, in general, reducing their usage while optimizing the production of polymer-based products. This aims to enhance the efficiency of the process and minimize the generation of waste and discarded materials during the production of the final product. Poly (lactic acid) (PLA) is a biodegradable aliphatic polyester resin and a sustainable alternative to current petroleum-based materials generally used for different industrial applications [6]. The quality of 3D-printed components, and thus their mechanical characteristics, is affected by various parameters like interlayer fusion, porosity, and swelling from natural fibers and particles.