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Research Papers

Effect of Fiber Content on Void Morphology in Resin Transfer Molded E-Glass/Epoxy Composites

[+] Author and Article Information
Youssef K. Hamidi

Ecole Nationale des Science Appliquées Safi, Université Cadi Ayyad, BP 63, 46000 Safi, Morocco

Sudha Dharmavaram, Levent Aktas

School of Aerospace and Mechanical Engineering, University of Oklahoma, Norman, OK 73019

M. Cengiz Altan1

School of Aerospace and Mechanical Engineering, University of Oklahoma, Norman, OK 73019altan@ou.edu

1

Corresponding author.

J. Eng. Mater. Technol 131(2), 021014 (Mar 09, 2009) (11 pages) doi:10.1115/1.3030944 History: Received May 30, 2005; Revised October 13, 2008; Published March 09, 2009

Effect of fiber volume fraction on occurrence, morphology, and spatial distribution of microvoids in resin transfer molded E-glass/epoxy composites is investigated. Three disk-shaped center-gated composite parts containing 8, 12, and 16 layers of randomly-oriented, E-glass fiber perform are molded, yielding 13.5%, 20.5%, and 27.5% fiber volume fractions. Voids are evaluated by microscopic image analysis of the samples obtained along the radius of these disk-shaped composites. The number of voids is found to decrease moderately with increasing fiber content. Void areal density decreased from 10.5voids/mm2 to 9.5voids/mm2 as fiber content is increased from 13.5% to 27.5%. Similarly, void volume fraction decreased from 3.1% to 2.5%. Increasing fiber volume fraction from 13.5% to 27.5% is found to lower the contribution of irregularly-shaped voids from 40% of total voids down to 22.4%. Along the radial direction, combined effects of void formation by mechanical entrapment and void mobility are shown to yield a spatially complex void distribution. However, increasing fiber content is observed to affect the void formation mechanisms as more voids are able to move toward the exit vents during molding. These findings are believed to be applicable not only to resin transfer molding but generally to liquid composite molding processes.

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Copyright © 2009 by American Society of Mechanical Engineers
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Figures

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Figure 1

Effect of fiber content on the inlet pressure profiles during molding

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Figure 2

Representative images of the composites molded with different fiber volume fractions, Vf, obtained at 200× magnification

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Figure 3

Effect of fiber content on void content and void areal density

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Figure 4

Effect of fiber content on (a) the contributions to void content and (b) void areal densities of voids encountered in different composite locations

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Figure 5

Effect of fiber content on void size distribution

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Figure 6

Effect of fiber content on size distributions based on (a) void content and (b) void areal density

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Figure 7

Effect of fiber content on voidage shape distribution based on (a) contribution to void content and (b) contribution to void areal density

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Figure 8

Effect of fiber content on the size distribution of irregular voids based on areal void density

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Figure 9

Effect of fiber content on radial variation in void content

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Figure 10

Effect of fiber content on the radial variation in the ratio of immobile to mobile void content

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