# Enhancing Structural Performance of Short Fiber Reinforced Objects through Customized Tool-Path
## 7 Summary  
A 3D printing methodology for fused deposition modeling (FDM) integrating fiber placement and tool-path development has been proposed. It starts with FEA to obtain principal stress fields and principal directions. Optimal fiber orientations of individual elements were determined. Using the stress output data from ABAQUS(tm), a tool-path optimization algorithm to maximize the effect  
\begin{table}
\begin{tabular}{c c c c} \hline \hline  & **Stiffness Response (N/mm)** & **Failure Strength (N)** & **Max Disp (mm)** \\ \hline Contour & 778.6 & 1330 & 2.18 \\ Optimized & 834.6 & 1430 & 2.19 \\ [\(\pm\)45\({}^{\circ}\)]s & 754.6 & 1287 & 2.10 \\ 0\({}^{\circ}\) only & 607.0 & 1073 & 1.87 \\ \hline \hline \end{tabular}
\end{table}
Table 4: Test results of stiffness response of CFRP-Nylon.  
Figure 31: Comparison of results between FEA simulation and experimental tests.  
Figure 30: Load vs. displacement curves of CFRP spur printed by various tool-path.  
of fiber reinforcement of CFRP was developed. To predict the mechanical behavior of the printed parts, G-codes from the tool-path were used to model printed objects.  
The proposed methodology demonstrates that the optimized tool-path can be applied to the 3D printer to extrude fibers aligned with principal directions. The flow distribution of printed fibers was verified by image analysis, which showed that approximately 83% of fibers were oriented as intended. Both FEA and preliminary experimental case study results show that CFRP-Nylon parts printed by the optimized tool-path achieved approximately 8% improvement in structural performance over parts printed at regular uniform printing direction. Associated experimental test results represent 15% lower stiffness responses than those from FEA predictions. Although 8% improvement is insignificant, nevertheless, with further AM printing process optimization to better control the fiber orientation, as well as advanced material development, the proposed customized tool-path method presented in this paper can be utilized as a design and printing methodology for CFRP structural parts by FDM technology.  
The proposed methodology can be extended to other materials. Moreover, with the development of a dual extruder system, dual material optimization would be another topic to overcome the brittle nature of CFRP. To predict their durability more accurately, fatigue tests are required. Due to the limitation of the current FDM printing system, only in-plane tool-path optimization has been allowed in this research. However, if AM with a tilted bed is fully developed, it may provide research opportunities for three-dimensional tool-path optimization.  
Conceptualization, B.S.K.; methodology, J.K.; software, J.K.; validation, J.K.; formal analysis, J.K.; investigation, J.K.; resources, J.K.; data curation, J.K.; writing--original draft preparation, J.K.; writing--review and editing, B.S.K. and J.K.; visualization, J.K.; supervision, B.S.K.; project administration, B.S.K.; funding acquisition, B.S.K. All authors have read and agreed to the published version of the manuscript.  
This research received no external funding.  
The authors declare no conflict of interest.