Performance of composite materials usually suffers from process-induced defects such as dry spots and 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 found to concentrate primarily 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, void content was found to fluctuate through-the-thickness of the composite. Variation up to 17% of the average void 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.

1.
Abraham
,
D.
,
Matthews
,
S.
, and
Mcllhagger
,
R.
,
1998
, “
A Comparison of Physical Properties of Glass Fiber Epoxy Composites Produced by Wet Lay-up With Autoclave Consolidation and Resin Transfer Moulding
,”
Composites, Part A
,
29A
, pp.
795
801
.
2.
Judd
,
N. C. W.
, and
Wright
,
W. W.
,
1978
, “
Voids and Their Effects on the Mechanical Properties of Composites an Appraisal
,”
SAMPE Q.
,
14
, pp.
10
14
.
3.
Goodwin, A. A., Howe, C. A., and Paton, R. J., 1997, “The Role of Voids in Reducing the Interlaminar Shear Strength in RTM Laminates,” Proceedings of ICCM-11, edited by M. L. Scott, Australian Composite Structures Society, Vol. IV, pp. 11–19.
4.
Harper
,
B. D.
,
Staab
,
G. H.
, and
Chen
,
R. S.
,
1987
, “
A Note on the Effect of Voids Upon the Hygral and Mechanical Properties of AS4/3502 Graphite/Epoxy
,”
J. Compos. Mater.
,
21
, pp.
280
289
.
5.
Patel
,
N.
, and
Lee
,
L. J.
,
1995
, “
Effect of Fiber Mat Architecture on Void Formation and Removal in Liquid Composite Molding
,”
Polym. Compos.
,
16
, pp.
386
399
.
6.
Mahale
,
A. D.
,
Prud’Homme
,
R. K.
, and
Rebenfeld
,
L.
,
1992
, “
Quantitative Measurement of Voids Formed During Liquid Impregnation of Nonwoven Multifilament Glass Networks Using an Optical Visualization Technique
,”
Polym. Eng. Sci.
,
32
, pp.
319
326
.
7.
Patel
,
N.
,
Rohatgi
,
V.
, and
Lee
,
J. L.
,
1995
, “
Micro Scale Flow Behavior and Void Formation Mechanism During Impregnation Through a Unidirectional Stitched Fiberglass Mat
,”
Polym. Eng. Sci.
,
35
, pp.
837
851
.
8.
Rohatgi
,
V.
,
Patel
,
N.
, and
Lee
,
J. L.
,
1996
, “
Experimental Investigation of Flow Induced Micro-Voids During Impregnation of Unidirectional Stitched Fiberglass Mat
,”
Polym. Compos.
,
17
, pp.
161
170
.
9.
Stabler
,
W. R.
,
Tatterson
,
G. B.
,
Sadler
,
R. L.
, and
El-Shiekh
,
A. H. M.
,
1992
, “
Void Minimization in the Manufacture of Carbon Fiber Composites by Resin Transfer Molding
,”
SAMPE Q.
,
23
January
, pp.
38
42
.
10.
Chan
,
A. W.
, and
Morgan
,
R. J.
,
1992
, “
Modeling Preform Impregnation and Void Formation in Resin Transfer Molding of Unidirectional Composites
,”
SAMPE Q.
,
23
April
, pp.
48
52
.
11.
Chui, W. K., Glimm, J., Tangerman, F. M., Jardine, A. P., Madsen, J. S., Donnellan, T. M., and Leek, R., 1995, “Porosity Migration in RTM,” in Proceedings of the 9th International Conference of Numerical Methods in Thermal Problems, pp. 1323–1334.
12.
Lundstro¨m
,
T. S.
,
1997
, “
Measurement of Void Collapse During Resin Transfer Moulding
,”
Composites, Part A
,
28A
, pp.
201
214
.
13.
Patel
,
N.
, and
Lee
,
J. L.
,
1996
, “
Modeling of Void Formation and Removal in Liquid Composite Molding. Part I: Wettability Analysis
,”
Polym. Compos.
,
17
, pp.
96
103
.
14.
Patel
,
N.
, and
Lee
,
J. L.
,
1996
, “
Modeling of Void Formation and Removal in Liquid Composite Molding. Part II: Model Development and Implementation
,”
Polym. Compos.
,
17
, pp.
104
114
.
15.
Binetruy
,
C.
,
Hilaire
,
B.
, and
Pabiot
,
J.
,
1998
, “
Tow Impregnation Model and Void Formation Mechanisms During RTM
,”
J. Compos. Mater.
,
32
, pp.
223
245
.
16.
Lundstro¨m
,
T. S.
,
1996
, “
Bubble Transport Through Constricted Capillary Tubes With Application to Resin Transfer Molding
,”
Polym. Compos.
,
17
, pp.
770
779
.
17.
Shih
,
C.-H.
, and
Lee
,
L. J.
,
2002
, “
Analysis of Void Removal in Liquid Composite Molding Using Microflow Models
,”
Polym. Compos.
,
23
, pp.
120
131
.
18.
Lundstro¨m
,
T. S.
, and
Gebart
,
B. R.
,
1994
, “
Influence from Process Parameters on Void Formation in Resin Transfer Molding
,”
Polym. Compos.
,
15
, pp.
25
33
.
19.
Choi
,
J. H.
, and
Dahran
,
C. K. H.
,
2002
, “
Mold Fill Time and Void Reduction in Resin Transfer Molding Achieved by Articulated Tooling
,”
J. Compos. Mater.
,
36
, pp.
2267
2285
.
20.
Olivero
,
K. A.
,
Barraza
,
H. J.
,
O’Rear
,
E. A.
, and
Altan
,
M. C.
,
2002
, “
Effect of Injection Rate and Post Fill Cure Pressure on Properties of Resin Transfer Molded Disks
,”
J. Compos. Mater.
,
36
, pp.
2011
2028
.
21.
Barraza
,
H. J.
,
Hamidi
,
Y. K.
,
Aktas
,
L.
,
O’Rear
,
E. A.
, and
Altan
,
M. C.
,
2004
, “
Porosity Reduction in the High-Speed Processing of Glass Fiber Composites by Resin Transfer Molding (RTM)
,”
J. Compos. Mater.
38
, pp.
195
226
.
22.
Ghiorse, S. R., 1991, “A Comparison of Void Measurement Methods for Carbon/Epoxy Composites,” U.S. Army Materials Technology Laboratory, Report No. MTL TR 91-13.
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