What is Vacuum assisted resin transfer molding?

Vacuum Assisted Resin Transfer Molding or Vacuum Injected Molding is a closed mold, out of autoclave composite manufacturing process. VARTM is a variation of Resin Transfer Molding with its distinguishing characteristic being the replacement of the top portion of a mold tool with a vacuum bag and the use of a vacuum to assist in resin flow. The process involves the use of a vacuum to facilitate resin flow into a fiber layup contained within a mold tool covered by a vacuum bag. After the impregnation occurs the composite part is allowed to cure at room temperature with an optional post cure sometimes carried out.