Damping properties of thermoplastic-elastomer interleaved carbon fiber-reinforced epoxy composites Hajime Kishi * , Manabu Kuwata, Satoshi Matsuda, Toshihiko Asami, Atsushi Murakami Graduate School of Engineering, Himeji Institute of Technology, University of Hyogo, 2167 Shosha, Himeji 671-2201, Japan Received 15 August 2003; received in revised form 28 April 2004; accepted 12 May 2004 Available online 6 July 2004 Abstract The aim of this study is to characterize the damping properties of carbon fiber-reinforced interleaved epoxy composites. Several types of thermoplastic-elastomer films, such as polyurethane elastomers, polyethylene-based ionomers and polyamide elastomers were used as the interleaving materials. The damping properties of the composite laminates with/without the interleaf films were evaluated by the mechanical impedance method. Also, the effects of the lay-up arrangements of the carbon-fiber prepregs on the damping properties of the interleaved laminates were examined. The viscoelastic properties of interleaved polymer films were reflect- ed in the damping properties of the corresponding interleaved laminates. The loss tangent of the interleaf films at the test temper- ature played an important roll in the loss factor of the interleaved laminates. Also, the stiffness of the films at the resonant frequency of the laminates was another important parameter that controlled the loss factor of the interleaved laminates. Ó 2004 Elsevier Ltd. All rights reserved. Keywords: Damping; Composites; A. Carbon fiber; Epoxy 1. Introduction Fiber-reinforced composites are now receiving greater attention in both the academic and industrial communi- ties. Industrial applications have been successful in sev- eral sectors including aerospace, automobile, marine, construction, sporting goods and power plants. The suc- cess of these fiber-reinforced composites is attributed to a large extent to their high specific strength, high modu- lus, light weight and affordable cost. The first generation of epoxy resins for use in carbon fiber-reinforced plastics (CFRP) optimized high modulus and high heat resis- tance by virtue of a high crosslink density. However, these rigid epoxy resins had low crack resistance, which was a major disadvantage for structural applications. Therefore, attention has been focused on toughening of matrix resins, using for example elastomer additions or thermoplastic polymer blends, in order to improve the impact resistance of CFRP laminates. However, an increase in matrix resin toughness beyond a certain level does not necessarily lead to the improvement of impact resistance of the composite laminates. This phenomenon has been explained as the result of a constraint effect on the plastic deformation zone due to the presence of rein- forcing fibers [1,2]. Another promising method has been to introduce a thin toughened resin layer between plies of the laminates [3,4]. The presence of a toughened inter- laminar layer with a certain thickness suppresses or de- lays the interlaminar damage, and the delamination resistance of the laminates under impact loading has been significantly improved [3,4]. Vibration and noise al- so constitute a major problem in the general use of ma- chines in aerospace, automobile and construction applications, where carbon fiber-reinforced composites 0266-3538/$ - see front matter Ó 2004 Elsevier Ltd. All rights reserved. doi:10.1016/j.compscitech.2004.05.006 * Corresponding author. Tel./fax: +81-792-67-4843. E-mail address: kishi@eng.u-hyogo.ac.jp (H. Kishi). www.elsevier.com/locate/compscitech COMPOSITES SCIENCE AND TECHNOLOGY Composites Science and Technology 64 (2004) 2517–2523