Investigation of mechanical properties of multi-walled carbon nanotubes/hollow glass microspheres – carbon fibre-reinforced epoxy composites in transverse fibre directions

Combining exceptional crushing strength of hollow glass microspheres (HGM) with reinforcing properties of carbon nanotubes as well as carbon fibres with epoxy resins results in a design poised to meet the demand for advanced, lightweight and high strength materials required in a variety of industries, such as aerospace and automotive, particularly, in the manufacture of composite rocket motor casings. In this study, unidirectional laminates of HGM/multi-walled CNTs (MWCNTs)/carbon-epoxy (CE) composites (samples nomenclature A–F) of varying wt.% of HGM and constant 0.1 wt.% of MWCNTs by filament winding technique were fabricated and subsequently cured. The HGM (iM16K) was varied as 0.2, 0.4, 0.6, 0.8, 1.0 wt.% by maintaining a constant concentration of 0.1 wt.% of MWCNTs. The hardener, fine hard (FH5200) was utilized in combination with epoxy resin (Epofine 1555). The epoxy resin was heated to 60°C after the fillers were added. Thermogravimetric analysis, differential mechanical analyzer and thermal mechanical analyzer were used to estimate the thermal stability, glass transition temperature and coefficient of thermal expansion (CTE), respectively. HGM and MWCNTs dispersion in the fracture samples caused by transverse tensile loading was examined using scanning electron microscopy. The effect of variation of HGM and 0.1 wt.% constant MWCNTs on tensile and compressive properties in transverse fibre directions of these composites has been investigated. Transverse tensile strength and tensile modulus were improved by 29.07 and 12.33%, respectively, up on the addition of 0.2 wt.% of HGM and 0.1 wt.% of MWCNTs in CE composite. The other findings indicated that > 0.2 wt.% HGM along with constant concentration of MWCNTs had decreasing effect on transverse tensile strength, modulus and compressive strength. The MWCNTs agglomeration was identified as the cause of these mechanical property degradations. The addition of HGM and MWCNTs decreased the CTE of the composite and increased the glass transition temperature as HGM limits the thermal motions of the epoxy polymer chain’s molecular segments. The HGM/MWCNTs/CE composite was shown to be thermally stable up to 310°C.