Bioinspired fracture toughness enhancement of a fully bio-based epoxy resin

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In this work, the concept of fracture toughness improvement via spatial variation of mechanical properties is applied to a composite with 100% bio-based carbon content based on epoxidized linseed oil. By proper selection of the hardener, either citric acid or sebacic acid, the mechanical properties were adjusted in a way that a bio-composite exhibits a stiff-soft-stiff layer architecture. Samples with two different thicknesses of soft interlayer (approx. 0.1 mm and 1.3 mm) were subsequently analyzed regarding their final performance. Specimen characteristics, owing to the curing and manufacturing process, were analyzed by means of local Fourier-transform infrared spectroscopy and differential scanning calorimetry. Fracture mechanics tests were performed to verify if the soft interlayer acts as a crack arrester. The results propose a high chemical compatibility between the used epoxy resins. Embedding a soft thin interlayer into a stiff resin matrix led to an increase in fracture toughness of 13 times, compared to the pure stiff resin. An increase in interlayer thickness led to a further increase in fracture toughness of 24 times. However, the stiffness decreased by 44% and 67%, respectively.
Original languageEnglish
Article number108098
Number of pages10
JournalPolymer Testing
Issue numberJuly
Publication statusPublished - Jul 2023

Bibliographical note

Funding Information:
Part of this research work was funded by the Federal Ministry for Climate Action, Environment, Energy, Mobility, Innovation and Technology in frame of the program “Produktion der Zukunft” under contract no. 871403 , within the context of the project “Semiflexible and flexible composites based on renewable resources”, as well as by the Federal Ministry for Transport, Innovation and Technology and the Federal Ministry for Digital and Economic Affairs in frame of the COMET-program under contract no. 854178 , within the COMET-project 3.S4 at the Polymer Competence Center Leoben GmbH (PCCL, Austria). The PCCL is funded by the Austrian Government and the State Governments of Styria, Lower Austria and Upper Austria . The funding of Montanuniversitaet Leoben for Open Access publishing is gratefully acknowledged.

Publisher Copyright:
© 2023 The Authors


  • Bio-based epoxy resin
  • Bio-composite
  • Epoxidized linseed oil
  • Fracture toughness
  • Layered structures
  • Material inhomogeneity

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