Characterization of carbon nanotube epoxy composites and carbon nanotubes/laminated carbon fibre epoxy composites

Over the last few decades carbon fibre reinforced polymer (CFRP) was used extensively because it offers attractive mechanical and thermal properties. Aircraft and some of high-end automobile constructions used CFRP, as it has an ability to be stuctured to aerodynamic efficient configurations. However, multi –layer laminates failure behavior is complex especially woven fabric composites. CFRPs’ typical failure modes include matrix fracture, interface debonding between fibre and matrix and interlaminar delamination. One of the techniques to overcome such failure modes is by reinforcing the composites with nanoparticles. In this study, the objective is to develop a tougher resin by dispersing multiwalled carbon nanotubes (MWCNTs) into the resin which will improve the properties of CFRP composites. Two types of MWCNTs were used which lengths, a) MWCNT_long (length 10-30 μm) and b) MWCNT_short (length 0.5-2 μm). There are two main parts in this thesis i.e., the investigation of mechanical and thermal properties of MWCNT_modified-epoxy and the investigation of mechanical properties of the MWCNT_filled-CFRP composite with an emphasis on interlaminar shear strength behaviour. In the first part, an experiment was conducted to investigate the dispersion quality of MWCNTs as nanofillers in the resin systems. The effect of MWCNTs on compressive and flexural properties of epoxy polymers were studied. The epoxy resin used was Epikote 828 and dapsone (DDS) as the hardener. The thermal properties of MWCNT_modified-Epikote 828 as compared to Epikote828/DDS neat systems were also investigated. From the results, the addition of MWCNT_short into Epikote 828 has significantly enhanced the compressive and flexural modulus. The second investigation was done to study the effect of MWCNT on the interlaminar shear strength (ILSS) properties of Epikote828/CFRP composite. A number of plane weave carbon fibre (CF) laminates were fabricated using the hand- layup technique, wet resin impregnation and vacuum bagging techniques. The quality of laminate such as void content, fibre and MWCNTs volume fraction was examined. Short beam shear (SBS) test was performed on the plane weave laminates to test the quality of ILSS. It was found that the ILSS of MWCNT_short/Epikote828/CF CFRP composite was better than the neat Epikote828/DDS CFRP composites. The addition of 0.38% of MWCNT_short improved the ILSS of the CF/Epikote828 by 14 %.

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