Determination of flow front velocity and optimal injection pressures for better impregnation of E-glass with polyester in resin transfer mold

et al. 2021

Funct. Compos. Struct.

Vacuum-assisted resin transfer molding (VaRTM) is becoming one of the most robust alternatives for autoclave processes. VaRTM, which applies the resin injection method in a vacuum environment, generally uses fiber reinforcement and a polymer matrix separately in the process. The VaRTM is mainly dominated by the characteristics of constituent materials, such as preform permeability and resin viscosity. Among them, process design with the arrangement of resin inlet/outlet locations is closely related to process defects, and inappropriate inlet/outlet layouts cause voids, etc, which has a decisive effect on quality degradation. Therefore, in this study, a highly curved and twisted spar structure was fabricated by the VaRTM, and both flow simulations using Programs for Applied Mechanics–Resin Transfer Molding software and experimental test parts built with three different inlet/outlet line conditions were performed and compared to predict and improve impregnation quality. There was good agreement between the simulation and built test specimen for the three cases that the shorter inlet and outlet length resulted in improved impregnation quality. It was verified that impregnation and inner quality could be improved through flow simulation analysis during the VaRTM process.

Section: Resultsmentioning

confidence: 99%

Improvement of impregnation quality on out-of-autoclave processed CFRP aircraft wing spar through resin flow simulation

et al. 2021

Funct. Compos. Struct.

“…When the infused resin moves to the marked line on mid cell, the elapsed time was captured. The measured resin flow-front location and elapsed time values were substituted into equation (2). Then, the Kozeny constant was obtained by using the calculated value in equation (5).…”

Section: Infusionmentioning

confidence: 99%

“…Permeability, a characteristic of porous medium, can be estimated from the pressure gradient and flow rate measured when a fluid is passed through a porous medium [1][2][3]. The permeability of fiber preforms can be obtained using this method because preforms can be assumed to be porous media, as shown in figure 1.…”

Section: Introductionmentioning

confidence: 99%

Prediction of permeability of five-harness satin fabric by a modified Kozeny constant determined from experiments

Kim

et al. 2022

Funct. Compos. Struct.

Permeability is a critical parameter not only in flow simulation analysis but also in liquid composite molding (LCM) process. When a liquid resin is infused into a dry preform, the impregnation is mainly characterized by the permeability. The permeability of a dry preform can be obtained through theoretical and experimental methods. In the theoretical estimation of permeability, the effects of fiber arrangement as well as fabric type and form for various types of preforms are not sufficiently reflected in the calculation. Thus, there is a gap between the theoretical and experimental permeability. Recently, experimental determination has been gaining considerable attention as a mean to obtain accurate permeability values; however, it requires a number of trials. In this study, the permeability of the Hexforce G0926 5HS (5-harness satin) carbon fabric preform is estimated using representative theoretical prediction models, the Gebart and Kozeny–Carman equations. In addition to the Kozeny–Carman permeability (using the Kozeny constant values from literature), the Kozeny constant obtained through experiments was used to obtain a modified Kozeny–Carman permeability. All three calculated permeabilities were compared and verified with the fabric manufacturer’s reference value. The results showed that the modified Kozeny–Carman permeability using the experimentally determined Kozeny constant was closest to the reference value at 57% fiber volume fraction. Further, the predicted permeability was compared with other experimental permeability values from literature over the 40%–65% range of fiber volume fraction. We found that the modified Kozeny–Carman permeability once again came closest to the literature values. Finally, an optimized fitting equation was proposed to replace the Kozeny–Carman equation for predicting the permeability of Hexforce G0926 5HS carbon fabric over the 40%–65% fiber volume fraction range.

“…[16] In RTM, optimum velocity and pressure which maximize the mechanical properties were found. [21,24] No related works are available in the literature for RI processes. In this study, low-velocity impact and tensile test have been chosen as representative tests to cover both in-plane and out-of-plane loads.…”

Section: Introductionmentioning

confidence: 99%

The mechanical effect of monitoring and controlling the impregnation in the resin infusion process

2022

Nowadays, most of industries are optimizing their processes to make their products more competitive. In the composites manufacturing industry, there is a big gap between the almost fully automated processes and those which require an intensive labor‐work. Although it has many advantages, the resin infusion process is characterized for its lack of automation. As a consequence, the results are strongly dependent on the process boundaries, the operator skills and expertise, and the result is usually far away from the optimum. In this work, the application of a novel methodology and its capability to maximize the mechanical properties of infusion‐manufactured composite materials is presented. After manufacturing stitched and unstitched materials at different impregnation velocities, an optimum value was assessed. The application of this value during the manufacture has increased the tensile and impact properties.