# Two Deformation Behaviors in Resin-Impregnated Glass Fibers under Different Flow Rates
## 5 Conclusions  
In this study, tow deformation in fiber reinforcements was experimentally examined under different flow rates and viscosity conditions. The permeability behaviors in double-scale porous media were observed under different hydrodynamic conditions to examine the overall tendencies of structural changes in the reinforcing fibers. Structural change was investigated in terms of the two representative indices of tow thickness (minor axis) and the major axis. The deformed tow behavior was examined microscopically to observe the behaviors of the tow under different flow rates. The main conclusions of this study are as follows:  
* Permeability increased with increasing flow rate; different permeability values were measured depending on the viscosity with increasing flow rates. Different permeability behaviors of the fluid in double-scale porous media were observed with different fluid viscosities, showing hysteresis between increasing and decreasing flow rates.
* The minor and major axes showed decreasing minimum values and increasing maximum values at different positions, respectively, which were caused by the different hydrodynamic entry lengths.  
Figure 8: Microscopic images of the tow in the fiber bundle from the inlet to the outlet position at 200 mm\({}^{3}\)/s of flow rate. (**a**): 60 mm, (**b**): 180 mm, (**c**): 300 mm, (**d**): 420 mm.  
Figure 9: Flow behavior in the double-scale porous media.  
* The different hydrodynamic forces exerted by the different flow rates resulted in the deformation of the tow as described by the major and minor axis changes.
* Microscopic analysis revealed deformed tows in the fiber bundles; tow fibers and fibers between the tows showed intra-tow and inter-tow regions, respectively.
* The flow in the double-scale porous media consisted of flow passage in the tow bundles, where most fluid passed through the inter-tow spaces and the rest through the intra-tow regions. Flow tended to be dominant in the intra-tow regions, and the tow bundles became more elliptical in shape as the flow rate increased.
* The present research regarding tow deformation in reinforcing fibers can be effectively used in future research on a wide range of LCM manufacturing processes. Our future research will focus on the tow deformation in reinforcing fibers with different treatments.  
Conceptualization, S.-H.K. and S.-W.C.; methodology, M.-X.L.; investigation, S.-W.C. and S.-H.K.; resources, M.-X.L.; data curation, J.-H.Y.; writing--original draft preparation, S.-W.C. and H.-M.Y.; writing--review and editing, S.-W.C. and H.-M.Y.; visualization, M.-X.L.; supervision, S.-W.C., M.-X.L., and H.-M.Y.; All authors have read and agreed to the published version of the manuscript.  
This research was supported in part by \"Regional Innovation Strategy (RIS)\" through the National Research Foundation of Korea (NRF) funded by the Ministry of Education (MOE), and in part by the National Research Foundation of Korea (NRF) grant funded by the Korean government (MSIP: Ministry of Science, ICT and Future Planning) (Grant No. NRF-2018R1C1B5086170).  
The study was conducted according to the guidelines of the Declaration of Applied Sciences, and approved by the Institutional Review Board of Gyeongsang National University.  
Not applicable.  
The authors declare that they have no conflict of interest.