<i>In-Situ</i> Void Content Measurements during Resin Transfer Molding

Performance of composite materials usually suffers from process-induced defects such as dry spots or microscopic voids. While effects of void content in molded composites have been studied extensively, knowledge of void morphology and spatial distribution of voids in composites manufactured by resin transfer molding (RTM) remains limited. In this study, through-the-thickness void distribution for a disk-shaped, E-glass/epoxy composite part manufactured by resin transfer molding is investigated. Microscopic image analysis is conducted through-the-thickness of a radial sample obtained from the molded composite disk. Voids are primarily found to concentrate within or adjacent to the fiber preforms. More than 93% of the voids are observed within the preform or in a so-called transition zone, next to a fibrous region. In addition, viod content was found to fluctuate through-the-thickness of the composite. Variation up to 17% of the average viod content of 2.15% is observed through-the-thicknesses of the eight layers studied. Microscopic analysis revealed that average size of voids near the mold surfaces is slightly larger than those located at the interior of the composite. In addition, average size of voids that are located within the fiber preform is observed to be smaller than those located in other regions of the composite. Finally, proximity to the surface is found to have no apparent effect on shape of voids within the composite.

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Optical Measurement of Preform Impregnation in Resin Transfer Molding

MRS Proceedings ◽

10.1557/proc-305-241 ◽

1993 ◽

Vol 305 ◽

Cited By ~ 3

Author(s):

Thomas Nowak ◽

Jung-Hoon Chun

Keyword(s):

High Performance ◽

Optical Measurement ◽

Resin Transfer Molding ◽

Void Formation ◽

Woven Fabric ◽

Void Content ◽

Trade Off ◽

Transfer Molding ◽

Scale Models ◽

Visualization Experiments

AbstractInfiltration of preforms used to manufacture high-performance, advanced polymer composites can lead to void formation due to inhomogeneities within the preforms. Void formation occurs at three distinct length scales: the fiber, tow and part scales. Flow visualization experiments were used to characterize void formation at the tow and fiber scales. Effects of tow-scale inhomogeneities were studied by varying the warp angle of a woven fabric. Effects of fiber-scale inhomogeneities were studied using scale models of typical tows. The experiments indicate that minimization of void content requires a trade-off between fiberscale and tow-scale void formation.

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Applying Magnetic Consolidation Pressure During Cure to Improve Laminate Quality: A Comparative Analysis of Wet Lay-Up and Vacuum Assisted Resin Transfer Molding Processes

Volume 14: Emerging Technologies; Materials: Genetics to Structures; Safety Engineering and Risk Analysis ◽

10.1115/imece2017-72019 ◽

2017 ◽

Author(s):

Maya Pishvar ◽

Mehrad Amirkhosravi ◽

M. Cengiz Altan

Keyword(s):

Composite Laminates ◽

Permanent Magnets ◽

Volume Fraction ◽

Resin Transfer Molding ◽

Void Content ◽

Fiber Volume ◽

Transfer Molding ◽

Consolidation Pressure ◽

A New Technique

This paper presents the application of a new technique, Magnet Assisted Composite Manufacturing (MACM), to enhance the quality of composite laminates fabricated by wet lay-up/vacuum bag (WLVB) and vacuum assisted resin transfer molding (VARTM). Towards this goal, a set of high-power, Neodymium permanent magnets, which are placed on a magnetic tool plate, is applied on the vacuum bag/lay-up. To further demonstrate the effectiveness of MACM, six-ply random mat, E-glass/epoxy composite laminates are produced under four processing scenarios: (i) Conventional WLVB; (ii) WLVB with magnetic consolidation; (iii) Conventional VARTM; and (iv) VARTM with magnetic consolidation. Applying magnetic consolidation pressure is found to be a convenient and efficient method for enhancing the overall quality of the laminates fabricated by WLVB and VARTM. For instance, in WLVB-MACM process, fiber volume fraction improves by 98% to 49% and void content reduces from 5% to less than 1.5% compared to conventional WLVB. These two factors lead to substantially increased mechanical properties of the WLVB-MACM laminates to a level comparable to those achieved by the higher-cost VARTM-MACM process.

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In-situ monitoring of the resin transfer molding impregnation and cure process

Polymer Engineering & Science ◽

10.1002/pen.760310110 ◽

1991 ◽

Vol 31 (1) ◽

pp. 56-60 ◽

Cited By ~ 17

Author(s):

D. Kranbuehl ◽

D. Eichinger ◽

T. Hamilton ◽

R. Clark

Keyword(s):

Resin Transfer Molding ◽

In Situ Monitoring ◽

Cure Process ◽

Transfer Molding

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Preparation of Glass Fabric/Poly(l-lactide) Composites by Thermoplastic Resin Transfer Molding

Polymers ◽

10.3390/polym11020339 ◽

2019 ◽

Vol 11 (2) ◽

pp. 339 ◽

Cited By ~ 4

Author(s):

Elodie Louisy ◽

Fabienne Samyn ◽

Serge Bourbigot ◽

Gaëlle Fontaine ◽

Fanny Bonnet

Keyword(s):

Resin Transfer Molding ◽

Bulk Polymerization ◽

Thermoplastic Resin ◽

Experimental Conditions ◽

Dynamic Vacuum ◽

Transfer Molding ◽

The Matrix ◽

Closed Mold ◽

Process Transfer

This study reports the first example of the production of polylactide composites prepared by Thermoplastic Resin Transfer Molding (T-RTM) via in situ bulk polymerization of l-lactide (l-LA) after injection in a closed mold containing glass fabrics. Tin octoate Sn(Oct)2 was used as the catalyst and first evaluated at the lab-scale in the experimental conditions required in the tank and in the mold of the RTM device. The reactions were then upscaled in the RTM in the absence of reinforcement to ensure the feasibility of the process (transfer and polymerization). Finally, poly-l-lactide (PLLA)-based composites with glass fabrics as the reinforcement were obtained. The resulting PLLA matrices exhibited conversions up to 99% along with high molar masses of up to 78,000 g·mol−1 when the polymerization was carried out under dynamic vacuum (vacuum-assisted RTM, VARTM). Moreover, a good impregnation of the glass fabrics by the matrix was observed by optical microscopy.

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