A Review of Liquid Injection Techniques for the Manufacture of Aerospace Composite Structures

This paper reviews the current state of liquid injection moulding technology for the manufacture of aerospace composite components. The requirements of the process are based on the material specifications, which stipulate low void contents below 1%, high volume fractions of fibre and an optimised cure cycle. The liquid injection process must also be economically competitive with current aerospace composite production techniques. Most liquid injection techniques have been developed with consideration for automobile requirements which mainly use glass fibre preforms at relatively low fibre volume fractions when compared with aerospace requirements. High production rates for automobile components are also necessary, which in most cases leads to high void contents. Polyester resins are also commonly used whereas aerospace demands the physical properties of epoxy resins. This review discusses reported investigations and possible process variations which have the potential to deliver economically competitive, high performance and high quality composite material when compared with current aerospace processing.