Mechanical energy dissipation using carbon fiber polymer–matrix structural composites with filler incorporation Seungjin Han • D. D. L. Chung Received: 2 September 2011 / Accepted: 17 October 2011 / Published online: 2 November 2011 Ó Springer Science+Business Media, LLC 2011 Abstract Continuous carbon fiber composites with enhanced mechanical energy dissipation (vibration damp- ing) under flexure are provided by incorporation of fillers between the laminae. Exfoliated graphite (EG) as a sole filler is more effective than carbon nanotube (SWCNT/ MWCNT), halloysite nanotube (HNT), or nanoclay as sole fillers in enhancing the loss tangent, if the curing pressure is 2.0 (not 0.5) MPa. The MWCNT, SiC whisker, and HNT as sole fillers are effective for increasing the storage modulus. The combined use of a storage modulus- enhancing filler (CNT, SiC whisker, or HNT) and a loss tangent-enhancing filler (EG or nanoclay) gives the best performance. With EG, HNT, and 2.0-MPa curing, the loss modulus is increased by 110%, while the flexural strength is decreased by 14% and the flexural modulus is not affected. With nanoclay, HNT, and 0.5-MPa curing, the loss modulus is increased by 96%, while the flexural strength and modulus are essentially not affected. The filler incorporation is more effective for crossply than unidirec- tional composites. The highest fraction of mechanical energy dissipated is 11%. The loss tangent enhancement is primarily contributed by the innermost interlaminar inter- faces, indicating shear deformation dominance in damping. The filler incorporation increases the interlaminar interface thickness, which remains below *10 lm. Introduction Mechanical energy dissipation (vibration damping) refers to the elimination of mechanical energy by conversion of the energy to another form of energy, which is commonly heat. The dissipation is important for almost any structure, particularly aircraft, satellites, spacecraft, cars, trains, boats, wind turbines, offshore oil tension leg platform tethers, optical equipment, rotating machinery (e.g., heli- copter rotors), robots, helmets, micromachines, micro- electronics, engines, bridges, and buildings. Dissipation results in numerous benefits, including noise reduction, less maintenance, longer life, better control of operations based on the structure, hazard mitigation, and enhanced resis- tance to mechanical threats (such as the impact of birds and hail on an aircraft). Vibration damping can be achieved passively or actively. Active damping involves the use of a coordinated set of sensor and actuator, so that the actuator suppresses the vibration through force application in real time as the vibration sensed by the sensor occurs. Due to the sensor and actuator, active damping is expensive. However, it is highly effective. A much less expensive and much more common method of damping is passive. In passive damping, materials that are effective for converting the mechanical energy to another form of energy, which is most commonly heat, are utilized for dissipating the energy associated with the vibration; sensors and actuators are not used. This article relates to passive damping. Damping ability is to be distinguished from toughness. The toughness of a material refers to the energy absorbed by the material in the entire deformation process up to failure. As a result, toughness is governed by the plastic deformation and fracture of the material and is a static mechanical property, as typically tested by increasing the S. Han  D. D. L. Chung (&) Composite Material Research Laboratory, University at Buffalo, State University of New York, Buffalo, NY 14260-4400, USA e-mail: ddlchung@buffalo.edu 123 J Mater Sci (2012) 47:2434–2453 DOI 10.1007/s10853-011-6066-7