| Popis: |
Epoxy is an important class of thermosetting material which have been used in many fields such as aerospace, automobile and energy sectors. cured epoxy, however, exhibits poor resistance to crack initiation and growth, thus low toughness and brittleness at failure. To improve the mechanical properties, in numerous studies the epoxy matrix in polymer composites has been modified by various techniques such as the inclusion of a second phase (e.g. core-shell rubber, thermoplastics or nanofillers). Inclusion of these materials in epoxy improves toughness and the impact resistance properties, but very few studies have focused on offering an ‘active toughening’ mechanism, meaning an increase in toughness activated by a stimulation (mechanical, electrical, thermal etc.) in high-performance rigid structures. In this study, aerospace grade epoxy resin modified with tetragonal barium titanate (BaTiO3) nanoparticles has been prepared, and its instantaneous toughening behaviour has been analysed under contact-less electromagnetic fields. For this reason, different wt.% of BaTiO3 nanoparticles (1, 5, 10 wt%) have been functionalised with silane coupling agents and dispersed uniformly into epoxy Araldite LY1564, a diglycidyl ether of bisphenol A (DGEBA) associated with its curing agent Aradur 3487. Real-time strain measurement (Tensile measurements) of the modified epoxy along with in-situ Raman shift study have been carried out in situ under an electric field stimulation. The results demonstrate that the activation of dipole displacements in BaTiO3 via an electromagnetic field introduces an interfacial compressive stress onto its surrounding rigid (fully cured) epoxy that enhances the toughness of the nanocomposite via suppressing the coalesce of inherent or process induced microcracks in the epoxy. The mechanism provides an effective route for mechanical property tailoring, specifically toughening of thermoset composites, under an electric field. The in-situ Tensile and Raman (during the stimulation) along with the materials characterisation (post stimulation) provides a unique quantitative framework for design of a toughening mechanism. |
