Mechanical and Thermal Properties of Carbonized PAN Nanofibers Cohesively Attached to Surface of Carbon Fiber Reinforced Composites Ibrahim M. Alarifi, 1 Abdulaziz Alharbi, 1 Waseem S. Khan, 2 AKM Samsur Rahman, 3 Ramazan Asmatulu* 1 Summary: Unidirecitonal pre-preg carbon fibers of ten peel plies were laid up at 0-, 45-, 45-, and 45-degree stacking sequences on a flat and smooth aluminum (Al) plate, and then carbonized electrospun polyacrylonitrile (PAN) nanofibers were placed on top of the last ply prior to vacuum curing in a vacuum oven. The PAN electrospun fibers were oxidized at 280  C in an ambient condition for 1 hr and then carbonized at 850  C for 1 hr in an argon (Ar) gas atmosphere. The resultant composite panels were cut into small pieces and subjected to a number of different characterization techniques. Thermal mechanical analysis (TMA) measurements clearly showed that significant reinforcement was achieved for the pre-preg/ carbonized PAN fiber composites because of the enhanced interfacial bonding between the PAN nanofibers and the matrix. Dynamic mechanical analysis (DMA) tests exhibited a shift of the glass transition temperature of the carbonized PAN nanofiber/composite, which may be helpful for high-temperature applications of the present composites. A Raman spectroscopy peak around 897 cm 1 indicated formation of the g-phase of the carbonized PAN fibers. The highest stretching peak of the CH 2 group was recognized within the range of 2,500–2,800 cm 1 for the carbonized fibers. The vibration peak of the C    N group also appeared at 1,452 cm 1 spectrum. TMA determined the coefficient of thermal expansion (CTE), indicating an improvement in stability of the composite material, which can be useful for structural health monitoring (SHM) as well as lightning strikes and electromagnetic interference shielding applications of new carbon fiber composites. Keywords: carbonization; carbon fiber composites; electrospun PAN nanofibers; thermal and mechanical properties Introduction Carbon fibers have been receiving signifi- cant attention due to their excellent properties, such as high mechanical strength and moduli, high thermal and electrical conductivity, good corrosion resistance, high fatigue strength, high creep resistance, and superior stiffness, and as such they are finding widespread applications in heat-treatment materials, high-temperature catalysts, sensors, com- posite-reinforcement materials, woven composites, structural laminates, mem- brane based-separation, nanoelectronics, and photonics. [1,2] Carbon nanofibers are multifunctional and one-dimensional nano- materials, which are being used in ad- vanced polymer matrix composites due to their outstanding properties and low density. [3] They behave elastically until failure, possess a low coefficient of thermal 1 Department of Mechanical Engineering, Wichita State University, 1845 Fairmount Street, Wichita, KS 67260, USA E-mail: ramazan.asmatulu@wichita.edu 2 Department of Mechanical and Industrial Engineer- ing, Majmaah University, Majmaah, Saudi Arabia 3 Department of Mechanical Engineering, Colorado State University, Fort Collins, CO 80523, USA Macromol. Symp. 2016, 365, 140–150 DOI: 10.1002/masy.201650003 140 | ß 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim wileyonlinelibrary.com