Determination of gel point and completion of curing in a single fiber/polymer composite

Hoffman, Joseph; Khadka, S.; Kumosa, M.

doi:10.1016/j.compscitech.2020.107997

Cited by 19 publications

(2 citation statements)

References 18 publications

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“…In terms of the fundamental characteristics, Hu [ 19 ] employed FBG sensors to monitor the shrinkage rate of composite materials and successfully obtained the gel point of resin. Hoffman [ 20 ] explored the gel point of epoxy resin during curing and the time required for complete curing, using FBG sensor and thermocouple to collect measurements. The study successfully obtained the curing curve of epoxy resin, with the experiment results verifying the applicability of the theoretical equation.…”

Section: Introductionmentioning

confidence: 99%

Using a Fiber Bragg Grating Sensor to Measure Residual Strain in the Vacuum-Assisted Resin Transfer Molding Process

2022

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Vinyl ester (VE) resin has strong environmental tolerance and is the matrix commonly used in the composite materials of fiber-reinforced plastics (FRP). VE resin is often combined with glass fiber in different maritime structures, such as wind turbine blades, spinner cases, and nacelle cases. However, VE resin exhibits exothermic reactions and shrinkage during curing, which often generates residual strain in large structures and those with a high stacking number. This study explored the exothermic reaction and shrinkage of VE resin and glass fiber during the vacuum-assisted resin transfer molding process, as measured using a fiber Bragg grating sensor. The experiment results verified the relationship between the stacking number and residual strain shrinkage. In addition, the symmetric laminate method was used to prevent the bending–twisting coupling effect and subsequent warping deformation of the FRP laminated plate during curing. The experiment results also verified that the bottom layers of the FRP laminated plates produced using VE resin were closer to the mold, and exhibited more shrinkage as the stacking number increased. In addition, this study discovered that during the experiment, the symmetry layer of the FRP laminated plate had a higher exothermic temperature than the bottom layer as a result of the symmetry layer’s ineffective heat dissipation. Therefore, the curing shrinkage of the symmetry layer resin was measured. The experiment results indicated that if the stacking number was between 10 and 30, the residual strain shrinkage of the symmetry layer was greater than that of the surface layer. However, because of the symmetric laminate, the residual strain of the symmetry layer did not increase when the temperature increased. Therefore, the greatest residual strain occurred at the surface of the bottom layer of the laminated plate with a stacking number of 40.

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Section: Introductionmentioning

confidence: 99%

Using a Fiber Bragg Grating Sensor to Measure Residual Strain in the Vacuum-Assisted Resin Transfer Molding Process

2022

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“…FBG sensors are used in thermosetting composites to detect gel points and measure the overall residual strain accumulated in the composite [4][5][6][17][18][19][20]. A gel point detection Measurement of transversal and axial residual strain during the curing [22] HB FBG (bow-tie fiber)…”

Section: Introductionmentioning

confidence: 99%

Gel Point Determination in Resin Transfer Molding Process with Fiber Bragg Grating Inscribed in Side-Hole Elliptical Core Optical Fiber

et al. 2022

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Material as well as process variations in the composites industry are reasons to develop methods for in-line monitoring, which would increase reproducibility of the manufacturing process and the final composite products. Fiber Bragg Gratings (FBGs) have shown to be useful for monitoring liquid-composite molding processes, e.g., in terms of online gel point detection. Existing works however, focus on in-plane strain measurements while out-of-plane residual strain prevails. In order to measure out-of-plane strain, FBG inscribed in highly birefringent fiber (HB FBG) can be used. The purpose of this research is the cure stage detection with (a) FBG inscribed in single mode and (b) FBG inscribed in highly-birefringent side-hole fiber in comparison to the reference gel point detected with an in-mold DC sensor. Results reveal that the curing process is better traceable with HB FBG than with regular FBG. Thus, the use of HB FBG can be a good method for the gel point estimation in the RTM process.

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In-Situ Determination of Degree of Cure by Mapping with Strain Measured by Embedded FBG and Conventional Sensor during VIM Process

et al. 2020

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Determination of gel point and completion of curing in a single fiber/polymer composite

Cited by 19 publications

References 18 publications

Using a Fiber Bragg Grating Sensor to Measure Residual Strain in the Vacuum-Assisted Resin Transfer Molding Process

Using a Fiber Bragg Grating Sensor to Measure Residual Strain in the Vacuum-Assisted Resin Transfer Molding Process

Gel Point Determination in Resin Transfer Molding Process with Fiber Bragg Grating Inscribed in Side-Hole Elliptical Core Optical Fiber

In-Situ Determination of Degree of Cure by Mapping with Strain Measured by Embedded FBG and Conventional Sensor during VIM Process

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