1 Int. J. Fatigue, vol., 54, 2013, 25-31 Enhanced Fatigue Behavior of a Glass Fiber Reinforced Hybrid Particles Modified Epoxy Nanocomposite under WISPERX Spectrum Load Sequence C.M. Manjunatha ∗,1 , Ramesh Bojja 1 , N. Jagannathan 1 , A.J. Kinloch 2 , A.C. Taylor 2 1 Fatigue and Structural Integrity Group, Structural Technologies Division, CSIR-National Aerospace Laboratories, Bangalore 560 017, India 2 Department of Mechanical Engineering, Imperial College London, South Kensington Campus, London SW7 2AZ, U.K. ABSTRACT Two types of glass fiber reinforced plastic (GFRP) composites were fabricated viz., GFRP with neat epoxy matrix (GFRP-neat) and GFRP with hybrid modified epoxy matrix (GFRP-hybrid) containing 9 wt. % of rubber microparticles and 10 wt. % of silica nanoparticles. Fatigue tests were conducted on both the composites under the WISPERX load sequence. The fatigue life of the GFRP-hybrid composite was about 4-5 times higher than that of the GFRP-neat composite. The underlying mechanisms for improved fatigue performance are discussed. A reasonably good correlation was observed between the experimental fatigue life and the fatigue life predicted under the spectrum loads. ∗ Corresponding author: Tel. +91-80-2508 6310; Fax: +91-80-2508 6301 E-mail address: manjucm@nal.res.in (CM Manjunatha)