Mechanical energy dissipation using carbon fiber polymer-matrix structural composites with filler incorporation

Continuous carbon fiber composites with enhanced mechanical energy dissipation (vibration damping) 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 unidirectional composites. The highest fraction of mechanical energy dissipated is 11%. The loss tangent enhancement is primarily contributed by the innermost interlaminar interfaces, indicating shear deformation dominance in damping. The filler incorporation increases the interlaminar interface thickness, which remains below ~10 μm.