Elevated-Temperature Thermal Conductivity for PEEK-Matrix Composite with Carbon Fibers, Graphite Flakes and PTFE

Abstract

An investigation on elevated-temperature thermal conductivity of PEEK-matrix composite containing PTFE particles, short carbon fibers and graphite flakes has been conducted. In the experimental phase of the study X-ray diffraction (XDR) is used to determine the morphology of neat PTFE and PEEK, PTFE/PEEK blend and the PTFE and PEEK phases in the CF/Gr/PTFE/PEEK composite. Optical and scanning electron microscopy work is performed to analyze the composite microstructure. The geometry, size, dispersion, and interfacial bonding of the fillers are assessed. The effective thermal conductivities of the composite and the neat polymers are determined by a modulated differential scanning calorimetry (MDSC) method with temperature ranging from -10 to 215°C. The results show that thermal conductivity of the composite with an increasing amount of graphite is affected by temperature and polymer transitions. In the theoretical phase of the study thermodynamic considerations are addressed with theoretical modeling. Different micromechanics models are used to determine the effective thermal conductivity of the composite. The thermal percolation results are compared well with experimental data. The results also indicate that thermal conductivity of the CF/Gr/PTFE/PEEK composite is affected by temperature and the volume fraction of graphite with a threshold 10% (by volume) where percolation occurs due to increasingly enhancing efficiency of thermal transport.