Effect of fiber geometry on the elastic constants of the plain woven fabric reinforced aluminum matrix composites Sang-Kwan Lee a, *, Joon-Hyung Byun a , Soon Hyung Hong b a Korea Institute of Machinery and Materials, 66 Sangnam-dong, Changwon, Kyungnam 641-010, South Korea b Department of Materials Science and Engineering, Korea Advanced Institute of Science and Technology, 373-1 Kusung-dong Yusung-gu, Taejon 305- 701, South Korea Received 20 May 2002; received in revised form 29 August 2002 Abstract The geometric and elastic models based on the unit cell have been proposed to predict the geometric characteristics and the elastic constants of plain woven carbon fabric reinforced metal matrix composites. In the geometric model, the inclined angle of the yarn crimp and the fiber volume fraction of woven composites have been predicted. In the elastic model, the coordinate transformation has been utilized to determine the elastic constants of the yarn crimp. The effective elastic constants have been obtained from the volume averaging of the elastic constants for constituent materials in composites. In order to verify the proposed model, plain woven carbon fabric reinforced Al matrix composites were fabricated using the vacuum assisted pressure infiltration casting process. Resonant ultrasound spectroscopy was performed to measure the effective elastic constants of the composites. Good correlation between the model predictions and the experimental results has been observed. Parametric study has been conducted to investigate the effect of various geometric parameters of plain weaves on the elastic constants of the composites. The yarn crimp angle, the gap length, fiber bundle size, the shape of yarn section, and the constituent materials have been examined in this study. Based on the proposed model, the effect of various geometric parameters and constituent materials on the three-dimensional elastic properties of woven fabric reinforced composites can be reasonably predicted. # 2002 Elsevier Science B.V. All rights reserved. Keywords: Metal matrix composites; Elastic constants; Carbon fibers; Al matrix; Woven fabric; Volume averaging method; Resonant ultrasound spectroscopy 1. Introduction Textile composites are structural materials reinforced with fibrous preforms, which are formed by textile processes such as a weaving, a braiding, or a knitting. Woven fabric composites are two-dimensional construc- tions where the warp and fill fiber bundles are interlaced with each other to form a layer. They are the most common type of textile preforms in structural applica- tions due to the balanced properties in the warp and fill directions, low manufacturing costs, easy forming of complex geometry, and high damage tolerance [1  /5]. The mechanical properties of woven fabrics are gov- erned by: (1) weave parameters such as an architecture pattern, yarn size, yarn spacing length, fiber crimp angle, and volume fraction of fiber bundles; (2) laminate parameters such as stacking orientation and overall fiber volume fraction. Although woven fabrics are the major reinforcements of polymer matrix composites, they provide many advantages in the application of metal matrix composites (MMCs): the increased transverse strength and stiffness and higher thermal stability. In order to fully realize the potential of woven fabric reinforced MMCs, it is imperative to understand the mechanical behavior as well as manufacturing process of the composites. Due to the wide range of constituent materials and fiber architectures available to woven fabric composites, it is necessary to develop a model, and to identify various effects of the geometric parameters on the elastic properties of textile composites. Technical papers on the * Corresponding author. Tel.:  /82-55-280-3314; fax:  /82-55-280- 3883 E-mail address: lsk6167@kmail.kimm.re.kr (S.-K. Lee). Materials Science and Engineering A347 (2003) 346  /358 www.elsevier.com/locate/msea 0921-5093/02/$ - see front matter # 2002 Elsevier Science B.V. All rights reserved. PII:S0921-5093(02)00614-7