Gradient interphases between high-Tg epoxy and polyetherimide for advanced joining processes

Julie Teuwen, Julien Asquier, P. Inderkum, K. Masania, C. Brauner, Irene Fernandez Villegas, C.A. Dransfeld

Research output: Chapter in Book/Conference proceedings/Edited volumeConference contributionScientificpeer-review

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Adhesive joining of carbon fibre reinforced polymer (CFRP) is cumbersome due to the careful surface preparation required and multiple validation steps to certify adhesion quality. Further these joints are often supplemented by mechanical fastenings add weight whilst also localising bearing stress. As an alternative technique, CFRP parts can be functionalized with thermoplastic surfaces during manufacture to enable cost-effective welding of composite structures. In the process of manufacturing the CFRP, curing an epoxy resin in the presence of the functionalising thermoplastic polymer can lead to local dissolution of the latter in the epoxy, followed by a reaction-induced phase separation. This results in a thermosetting-thermoplastic interphase featuring gradient concentrations and a multiphase morphology, which promotes load transfer between the thermosetting matrix and the thermoplastic joint. The aim of the work presented in this paper was to investigate interphase formation between high-Tg epoxy and polyetherimide (PEI) at different curing temperatures. The morphology was characterised using scanning electron microscopy and the composition of the interphase was quantified through Raman spectroscopy. The curing experiments indicated that temperature has a significant effect on the interphase morphology and led to two different biphasic morphologies which generally increased in size with increasing curing temperature. This suggests that the size of the gradient interphase can be tailored through the curing process, which is as a fundamental step in optimising the structural performance of welded joints with PEI-functionalized epoxy-based CFRPs.
Original languageEnglish
Title of host publicationProceedings of the 18th European Conference on Composite Materials
Subtitle of host publication24-28th June 2018, Athens, Greece
Number of pages9
Publication statusPublished - 2018
EventECCM18: 18th European Conference on Composite Materials - Athens, Greece
Duration: 24 Jun 201828 Jun 2018
Conference number: 18


ConferenceECCM18: 18th European Conference on Composite Materials
Abbreviated titleECCM18
Internet address


  • thermoset
  • thermoplastic
  • welding
  • solubility
  • interphase
  • phase separation


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