## 4 Properties of 3D Printed Pla-Metal Biocomposites
### Mechanical Properties
Although other parameters contribute to impact strength, infill density (58.12%) is the most important factor determining tensile strength (30.82%), flexural strength (44.02%), and other parameters, in that order. The examiners recorded the maximum values for flexural strength (19.3 N/mm), impact strength (0.26 kJ/m), and tensile strength (36.08 N/mm). Given the current limitations of the FDM process when it comes to brass alloy properties, this study aims to fill that gap by analyzing the bend and compression characteristics of FDM-printed parts with different infill patterns and 15% and 70% wt. of brass-reinforced PLA from an examiner's perspective. The relevant ASTM standards guided both the sample processing and analysis. Compared with casting or sintering materials, the mechanical nature of 3D-printed objects will be inferior due to the weak connection between successive layers. The orientation among the printed layers might therefore significantly impact the products' behavior. The authors of another study mechanically evaluated a 3D-printed composite that uses PLA with bronze filler as an alternative to sintered bronze components under compression loads [107]. The stress-strain curves in ambient temperature and the transitional glass zone were determined by subjecting cylindrical specimens grown having the base horizontally or vertically to compression loads. This study filled a gap in the literature by investigating the potential of bronze-filled PLA as a material for gaskets and other compression-sensitive items [108]. Additionally, bend and compression characteristics were best captured by the grid pattern, while the concentric pattern was determined to be the optimal printing pattern [109]. Although the addition of Ti64 raised PLA's glass transition temperature, it had a slight negative impact on the filament's thermal stability, melting point, and crystallization point. Before adding from 3 to 6 wt. % of Ti64, the mechanical properties of PLA were already good. However, PLA-3 Ti64's maximum compressive strength and compressive modulus went up by 50 MPa and 2 GPa, respectively. The flowability tests also confirmed that all composite filaments were print-ready. PLA-ZnOMA additionally obtained elastic modulus values near 1 GPa, making them suitable for use in bone applications [110]. When tested for cell activities, PLA-ZnOMA scaffolds encouraged mesenchymal adult stem cells to change into osteoblasts, and the survival rate of these cells was 160% higher than that of the untreated samples. The untreated samples did not have the right flexibility for bone use, but tests showed that ZnOAM biocomposites did have it. Cell viability was better in PLA/ZnOAM scaffolds compared to PLA/ZnO composites with treated filler surfaces, even though the untreated samples showed more bioactivity [111]. Finally, the tensile test results show that the octa-spiral pattern is the weakest and the concentric pattern is the strongest for both compositions, with the highest values for elastic modulus and ultimate tensile strength as well as yield strength. A maximum of 0.3 GPa, 8 MPa, and 5 MPa were achieved for the ultimate tensile strength, yield strength, and elastic modulus, respectively [112]. Figure 11 shows the compressive stress vs. strain graph for PLA-Mn composites. It was observed from the test results that 7% Mn particles enhanced the mechanical properties of the PLA-biocomposites. The impact of two compositions and five infill patterns on bend and compression characteristics was evaluated using RSM [114]. Next, the intended bending and compression characteristics are predicted using a prediction model. The results demonstrate that the specimens with a 15 wt. % brass composition exhibit superior characteristics when contrasted with those with a 70 wt. % brass composition. This is because the interlayer bonding energy with the PLA was reduced because of an increase in the weight% of brass composition.