Composites made with synthetic epoxy and bio-epoxy made from Castor oil were compared in terms of their performance characteristics. Both types of epoxy make use of glass fibre as a reinforcement material. Using a vacuum-assisted resin transfer moulding process, the composite structure was made and cured for 24 h at room temperature. Thermal, chemical, and combustibility properties were measured for both. The inclusion of Castor bio-epoxy slightly improved the matrix’s thermal constancy among 294 and 375 ℃, as shown in thermogravimetric analysis. Tg trends derived by differential scanning calorimetry curves were validated by DMA curves, which also showed a slight performance drop. However, the composite that included Castor bio-epoxy had a flammability rating of horizontal burning (HB) and required half as much time to self-extinguish as the entirely synthetic composite. To determine whether or not the spectral differences between the two specimens were caused by the bonding type, attenuated total reflectance by the infrared Fourier transform (FT-IR/ATR) was used. The blended bio-epoxy composite specimen showed superior thermal stability, identical flammability characteristics, and comparable performance. This research proposed using bio-based epoxy as an alternative to synthetic epoxy to decrease the environmental impact of non-renewable composites. © 2025 Elsevier B.V., All rights reserved.