Flame resistant performance of nanocomposites coated with exfoliated graphite nanoplatelets/carbon nanofiber hybrid nanopapers Jinfeng Zhuge 1 , Jihua Gou 1, * ,† and Christopher Ibeh 2 1 Composite Materials and Structures Laboratory, Department of Mechanical, Materials and Aerospace Engineering, University of Central Florida, Orlando, FL 32816 USA 2 Center for Nanocomposites and Multifunctional Materials, Pittsburg State University, Pittsburg, KS 66762 USA SUMMARY Exfoliated graphite nanoplatelets (xGnPs) were used to improve the flame resistant performance of glass fiber‐reinforced polyester composites. Along with xGnP, traditional intumescent fire retardant ammonium polyphosphate (APP) was introduced into the polymer matrix as the dominant additive to reduce the heat release rate (HRR) and total heat released (THR) of the composites. The cone calorimeter test results Indicate that the optimal weight ratios of xGnP and APP were 3% and 17% by weight, respectively. At such weight ratio, a synergistic effect between xGnP and APP was demonstrated. The flame resistant performance of the nanocomposites was further improved by applying xGnP‐dominant carbon nanofiber (CNF)/xGnP hybrid nanopaper onto the surface of the samples. Compared with the control sample, the integration of the HRR (THR) from 0 to 100 s of the sample coated with the nanopaper of CNF/xGnP = 1/3 shows more than 30% decrease in THR. Based on the results of mass loss, the nanopaper coating is also shown to enhance the structural stability of the samples under fire conditions, which affects the mechanical properties of the composites. The results show that the thermal properties, permeability of composites, and char formation play important roles in determining the fire behavior of the composites. Copyright © 2011 John Wiley & Sons, Ltd. Received 25 October 2010; Revised 21 March 2011; Accepted 26 April 2011 KEY WORDS: exfoliated graphite nanoplatelets; nanopaper; nanocomposites; permeability; synergistic effect 1. INTRODUCTION Fiber reinforced polymers (FRP) have excellent physical and mechanical properties, such as high specific strength, light weight, good fatigue, and corrosion resistance. They have become viable alternatives to conventional metallic materials in many industries such as aircraft, marine structures, ships, buildings, transportation, electrical and electronics components, and offshore structures. However, since FRP contains polymer matrix, the composites and their structures are combustible. FRP will degrade, decompose, and sometimes yield toxic gases at high temperature or subject to fire conditions. Due to their combustible nature, fire safety and fire protection of FRP are of great concern. Consequently, improving the flame resistance of polymers is crucial to increase the utilization of FRP. Understanding the combustion process of composite laminates has led to the knowledge that fire resistant performance can be improved chemically and physically in both vapor phase and condensed phase of the combustion process by controlling the heat and/or fuel to keep it below a critical level. In *Correspondence to: Jihua Gou, Department of Mechanical, Materials and Aerospace Engineering, University of Central Florida, Orlando, FL 32816, USA. † E‐mail: jihua.gou@ucf.edu Copyright © 2011 John Wiley & Sons, Ltd. FIRE AND MATERIALS Fire Mater. 2012; 36:241–253 Published online 22 June 2011 in Wiley Online Library (wileyonlinelibrary.com). DOI: 10.1002/fam.1104