Sustainable epoxy based biocomposites reinforced with Melilotus officinalis: Structural, mechanical, thermal, and dielectric performance evaluation

The aim of this study is to investigate the manufacturability of Melilotus officinalis (L.) reinforced epoxy biocomposites as a renewable biofiller and to characterize the mechanical, thermal, and dielectric properties of these materials. For this purpose, composites containing biomass at 0, 3, 6, and 9 wt.% were prepared; the samples were examined by tensile testing, FTIR, SEM, EDX, XRD, Shore D hardness, thermal conductivity, and dielectric analysis. The findings showed that with increasing M. officinalis content, tensile strength, hardness, and density decreased, while ductility and elongation at break improved. The significant decrease in thermal conductivity revealed an increase in heat insulation efficiency. Dielectric analyses showed that strong interfacial polarization occurred at low frequencies, and the dielectric constant and loss values ​​decreased as the frequency increased. SEM examinations confirmed that the plant-derived filler was homogeneously distributed and formed acceptable interfacial adhesion with the matrix. In conclusion, although the use of synthetic epoxy matrix and the decrease in mechanical strength limit load-bearing structural applications, M. officinalis is a promising biofiller for lightweight and partially bio-based epoxy composites thanks to its increased ductility and improved thermal insulation properties. © The Author(s) 2026. This article is distributed under the terms of the Creative Commons Attribution-NonCommercial 4.0 License (https://creativecommons.org/licenses/by-nc/4.0/) which permits non-commercial use, reproduction and distribution of the work without further permission provided the original work is attributed as specified on the SAGE and Open Access pages (https://us.sagepub.com/en-us/nam/open-access-at-sage).