## 4 Properties of 3D Printed Pla-Metal Biocomposites  
### Mechanical Properties  
One way to make AM PLA stronger, since it was not strong enough for many real-world applications, is to add copper powder to make a new material called PLA-Cu. A universal testing machine and Hopkinson pressure bar equipment were used to examine how PLA and PLA-Cu respond to different types of stress [93]. This experimental study developed a constitutive model based on the mechanical behavior of each material. Impact embrittlement influences PLA-Cu, meaning it acts in a straightforward, predictable way when under fast-moving conditions [94]. Both the composite and the pure PLA react differently to changes in speed from static to dynamic condition, but adding copper powder significantly increased the strength needed to make them deform due to the ductility and load-bearing capacity of the copper. To better predict how these materials behave under different loads, the Johnson-Cook constitutive equation was adjusted by including the Cowper-Symonds strain rate term. The results provided valuable information for numerical models for PLA with copper in Figure 9[95]. The effect of FDM settings on the compressive strength of composites with PLA and copper filler. Researchers examined the impact of changing process parameters on flexural, tensile, and impact strengths [96]. By manipulating the process parameters, mathematical models were created to forecast the composite strength. As the printing speed and thickness of the layers increased, the composites' strength decreased. Conversely, the composites' strength was enhanced by raising the nozzle temperature along with infill density. To gain insight into the mechanisms of fracture, characterization analysis was applied to the composite samples. The specimens that are affected by the method parameters that affect layer bonding and porosity exhibit both brittle and tensile modes of failure [97]. To find out the strength of two important materials, three different layer arrangements of PLA and  
\begin{table}
\begin{tabular}{c c c c c} \hline
**S.No. ** & **Biocomposite** & **AM Technique** & **Process Parameters** & **Reference** \\ \hline \multirow{3}{*}{4} & PLA Copper & \multirow{3}{*}{FDM} & Nozzle temperature—200–230 \({}^{\circ}\)C, & \multirow{3}{*}{[85]} \\  & biocomposites & & & \\  & & & & \\ \hline \multirow{3}{*}{5} & PLA with Copper & \multirow{3}{*}{FDM} & Nozzle diameter—0.4 mm, Layer & \multirow{3}{*}{[86]} \\  & biocomposites & & & \\  & & & & \\  & & & & \\  & & & & \\  & & & & \\ \hline \multirow{3}{*}{6} & PLA with Silver & \multirow{3}{*}{FDM} & Nozzle diameter—0.4 mm, Nozzle & \multirow{3}{*}{[87]} \\  & biocomposites & & & \\  & & &PLA/Cu were used to create and test dog bone samples. The test results show that adding copper to 3D-printed PLA samples increases their maximum tensile strength by about 16% when flat, 14% when on the edge, and 10.4% when standing upright. The LCCs of samples with pre-existing cracks could be estimated using the Equivalent Material Concept (EMC) along with the Average Strain Energy Density (ASED) method, as well as through actual testing. By using the EMC-ASED criterion, the measured LCCs of FDM-PLA and FDM-PLA/Cu samples could be accurately estimated [50]. Understanding the fundamental mechanics of FDM-printed parts is essential for engineers. Because of its low cost and precise dimensional processing capabilities, FDM has seen extensive use in AM for processing complicated parts. The filament-shaped thermoplastic polymers are the main components. The FDM method, applied to PLA and PLA/Cu, aims to develop testing samples with different infill percentages (25, 50, and 75%) and designs [98]. After that, tensile testing is employed to evaluate the mechanical characteristics of copper. The results indicate that the best tensile strength performance was achieved with the infill design using a triangle PLA/Cu sample and a concentric PLA specimen with a 75% infill percentage.