This paper presents a detailed study of the relationship between phase morphology and fracture toughness of two types of thermoplastic modified epoxy resins, a tetrafunctional and a bifunctional type. The reaction-induced phase separation of the thermoplastic (TP) during curing leads to distinct morphologies, depending on the modifier content and the functionality of the matrix. This, in turn, impacts the fracture toughness of modified epoxy resins. A transition from a particulate to a co-continuous morphology is observed at sufficiently high TP content (20 wt%) in both epoxy systems. Thermoplastic phases exhibit a significant level of plastic deformation during crack propagation followed by tearing or debonding, depending on the composition. This, in addition to the formation of shear bands in the matrix, is the most dominant energy dissipation mechanism. Higher viscosity and cross-link density of the tetrafunctional epoxy result in the formation of uniformly distributed submicron-sized thermoplastic particles, where the limited diffusion growth of thermoplastic phase, following the onset of phase separation, is further restricted.
- Crack bridging
- Fracture toughness
- Phase morphology
- Reaction-induced phase separation
- Shear banding
ASJC Scopus subject areas
- Organic Chemistry
- Polymers and Plastics
- Materials Chemistry
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Phase Morphology and Fracture Toughness of CNT/Polyetherimide Modified Epoxy Polymer Nanocomposites as Matrices for Advanced CFRP CompositesAuthor: Ma, H., Jul 2020
Student thesis: Doctoral Thesis › Doctor of Philosophy