Browsing by Author "Kumar, Vijay Thakur"

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    Accelerated microwave curing of fibre-reinforced thermoset polymer composites for structural applications: A review of scientific challenges
    (Elsevier, 2018-09-12) Mgbemena, Chinedum Ogonna; Li, Danning; Lin, Meng-Fang; Liddel, Paul Daniel; Katnam, Kali Babu; Kumar, Vijay Thakur; Nezhad, Hamed Yazdani
    Accelerated curing of high performance fibre-reinforced polymer (FRP) composites via microwave heating or radiation, which can significantly reduce cure time and increase energy efficiency, has several major challenges (e.g. uneven depth of radiation penetration, reinforcing fibre shielding, uneven curing, introduction of hot spots etc). This article reviews the current scientific challenges with microwave curing of FRP composites considering the underlying physics of microwave radiation absorption in thermoset-matrix composites. The fundamental principles behind efficient accelerated curing of composites using microwave radiation heating are reviewed and presented, especially focusing on the relation between penetration depth, microwave frequency, dielectric properties and cure degree. Based on this review, major factors influencing microwave curing of thermoset-matrix composites are identified, and recommendations for efficient cure cycle design are provided.
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    Towards the use of electrospun piezoelectric nanofibre layers for enabling in-situ measurement in high performance composite laminates
    (European Society for Composite Materials, 2018-06-30) Lotfian, Saeid; Kumar, Vijay Thakur; Giraudmaillet, Claire; Yoosefinejad, Ata; Brennan, Feargal; Yazdani Nezhad, Hamed
    The aim of this research is to highlight the effects from composite manufacturing on the piezoelectric properties of fibre-reinforced composite laminates internally modified by layers of low-density piezoelectric thermoplastic nanofibres in association with a conductive electrode layer. for in-situ deformation measurement of aerospace and renewable energy composite structures through enabling electrical signal change. Several methods have been used to analyse the effects such as phase characterisation of the piezoelectric thermoplastic nanofibres and non-destructive inspection of the laminates, during processing an Inter Digital Electrode (IDE) made by conductive epoxy-graphene resin, and pre-preg autoclave manufacturing aerospace grade laminates. The purpose of fabrication of such IDE layer was to embed the same resin type (HexFlow® RTM6) for the conductive layer as that used for the laminates, in order to sustain the structural integrity via mitigation of downgrading effects on the bonding quality and interlaminar properties between plies, rising from materials mismatch and discontinuous interplay stress transfer. XRD, FTIR, EDS and SEM analyses have been carried out in the material characterisation phase, whereas pulsed thermography and ultrasonic C-scanning were used for the localisation of conductive resin embedded within the composite laminates. This study has shown promising results for enabling internally embedded piezoelectricity (and thus health monitoring capabilities) in high performance composite laminates such as those in aerospace, automotive and energy sectors.