The amine:epoxide ratio at the interface of a glass fibre/epoxy matrix system and its influence on the interfacial shear strength

Helga Nørgaard Petersen, R. F. Minty, James L. Thomason, L. Yang, Yukihiro Kusano*, Povl Brøndsted, Kristoffer Almdal

*Corresponding author for this work

Research output: Contribution to journalJournal articleResearchpeer-review


The interfacial shear strength (IFSS) is commonly used for evaluating the adhesion at the interface between fibre and matrix. A glass fibre/epoxy matrix system was investigated. The surface coatings applied to glass fibres may result in a discrepancy in the amine:epoxide group ratio between the interface and the bulk matrix, consequently moving the ratio away from the optimum stoichiometric ratio most often used. The amine:epoxide group ratio in the matrix was varied to obtain the optimum ratio at the interface. The study found that the amine:epoxide ratio influenced the IFSS with an optimum just below the stoichiometric ratio. The microbond test was conducted in a thermal mechanical analyser (TMA) to determine the IFSS thus revealing an inverse dependency on the testing temperature: an increased testing temperature yields a decrease of IFSS. IFSS determined at temperatures below the glass transition temperature displays a decreasing trend at high amine:epoxide ratio whereas IFSS measured at testing temperatures above the glass transition temperature steadily increases as the amine:epoxide ratio increases. The microbond test was conducted using both a tensile tester and a TMA setup. The two microbond test setups yielded results with same behaviour of the IFSS as a function of the amine:epoxide ratio.
Original languageEnglish
JournalComposite Interfaces
Issue number6
Pages (from-to)493-505
Number of pages12
Publication statusPublished - 2019


  • Fibre/matrix bond
  • Interface sizing
  • Stress transfer
  • Interfacial Shear Strength (IFSS)

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