A dynamic mechanical analysis was undertaken to determine the influence of moisture on the mechanical properties of interwoven hemp/polyethylene terephthalate (PET) hybrid composites. Composite laminates were fabricated using vacuum infusion process; form epoxy resin reinforced with interwoven hemp and PET fibres. Woven hemp, woven PET, and interwoven hemp/PET hybrid composites were produced. The hybrid hemp/PET composites yielded the highest final residue % due to the PET fibres which improved the thermal stability. The glass transition temperatures of the woven hemp, woven PET, and interwoven hemp/PET hybrid composites were 68, 67, and 69 °C, respectively. Water absorption tests were conducted, and tensile and flexural tests were conducted on the wet and dry specimens. The water uptake of the hemp/PET hybrid composite was half that of the woven hemp composites. The tensile and flexural strengths of the interwoven hemp/PET hybrid composites were 4% and 22% greater than those of the woven hemp composites, respectively.
This paper presents a study on dynamic mechanical analysis (DMA) of graphene nanoplatelets (GNPs)/glass reinforced epoxy composite. The composite was fabricated by a hand lay-up technique followed by vacuum bagging technique. GNPs weight fraction was 0.5 and 1.5 wt.% for a fixed glass fibre fraction. The test was carried out in terms of storage modulus (E’), loss modulus (E”), and tan δ. The result indicates that 1.5 wt.% GNPs/glass reinforced epoxy composite obtain the maximum value of the dynamic mechanical properties due to the incorporation of GNPs nanofiller. The improved dynamic mechanical properties were related to better interfacial interaction of the nanofiller with the epoxy matrix. The glass transition temperature (Tg) value for 0.5 and 1.5 wt.% GNPs/glass were 62.84 and 66.01 °C, respectively.
The damage self-sensing and strain monitoring of glass-reinforced epoxy composites impregnated with graphene nanoplatelets (GNPs) and multiwalled carbon nanotubes (MWCNTs) were investigated. Hand lay-up and vacuum bagging methods were used to fabricate the composite. Mechanical stirrer, high shear mixer, and ultrasonic probe were used to mix the nanofiller and epoxy. The loadings of the nanofiller used were 0.5, 1.5, 3, and 5 wt%. The specimens were tested using in situ electromechanical measurements under mechanical tests. The results show that the type and weight content of the nanofiller affect the electrical properties, damage self-sensing behaviour, and mechanical properties of the composites. The electrical conductivity of the GNP-glass and MWCNT-glass composites increased with nanofiller content. The tensile and flexural strengths of the composite improved with the addition of GNP and MWCNT nanofillers from 0.5 to 3 wt%. The 3 wt% nanofiller loading for GNP and MWCNT produces better mechanical–electrical performance. Field emission scanning electron microscopy revealed the dispersion of GNP and MWCNT nanofillers in the composites.
In this study, the effect of water uptake on graphene nanoplatelets (GNP) and multiwalled carbon nanotube (MWCNT)-impregnated glass-reinforced epoxy composites was examined. The composite was manufactured using a hand lay-up and vacuum bagging technique. The nanofiller was mixed with epoxy using a mechanical stirrer, high-shear mixer, and ultrasonic probe machine. In situ electromechanical testing was performed on the specimens. The study found that the weight content and type of nanofiller impact the composites' water uptake and mechanical properties. The water uptake of GNP–glass, MWCNT–glass, and GNP–MWCNT–glass hybrid composites decrease with the addition of different nanofiller contents. Adding a 1.5 GNP–MWCNT hybrid mixture increased the composite's tensile and flexural strengths to 269.3 and 294.4 MPa, respectively. The GNP–MWCNT–glass hybrid composite shows a positive synergy effect on the enhancement of water-ageing with self-sensing ability, while the GNP–glass, MWCNT–glass composites show a less positive effect on water ageing sensing behaviour. The nanofillers dispersion and fracture surface morphological observations were disclosed using a field emission scanning electron microscope. The results established that the GNP–MWCNT–glass hybrid exhibits good potential for in situ damage monitoring of composites and can support their development and application as a smart material.
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