A method of forming a fiber reinforced composite structure having a fiber volume fraction (14) below 50 vol.-% using vacuum bag molding, the method comprising the steps of placing an assembly of fiber laminates (3) on a tool surface (1.1), creating a predetermined maximum difference of pressure (10) between the inside and the outside of an airtight envelope (4), infusing resin into the assembly of fiber laminates (3), reducing the difference of pressure between the inside and the outside of the airtight envelope (4), so that the assembly of fiber laminates (3) expands and the infusion of resin into the assembly of fiber laminates (3) continues thus forming a resin infused assembly of fiber laminates (3), and curing the resin infused assembly of fiber laminates (3).