In the present disclosure!, there is disclosed an epoxy resin formulation for the manufacturing of large and thick composite structures, said formulation comprising i) at least one epoxy resin in a weight proportion varying between 50 parts to 70 parts; (ii) at least one hardening agent in a weight proportion varying between 21 phr to 29 phr; (iii) at least one diluent in a weight proportion varying between 10 phr to 40 phr; and (iv) N,N′dimethylaminopropylamine as an accelerator in a weight proportion varying between 0.5 phr to 3.0 phr. The formulation is used in the manufacturing of large and thick composite structures by employing Vacuum Assisted Resin Transfer Molding Process.