Most aerospace composite structures are produced today using prepreg and autoclave cure. Recently an increasing number and type of large and critical structures are being manufactured in a very different way – using Preforms assembled from dry fabrics and tapes and then infusing the epoxy resin into the Preform followed by cure. If the infusion is performed in a matched closed mold under high pressure, the process is called RTM. For many larger parts, infusion is performed using vacuum pressure only with single surface tools. This process has many different names reflecting slight differences in the infusion process including VARTM, CAPRI, VAP, RTI, RFI, BRI, SCRIMP and several others.
A wide range of aerospace parts are fully qualified and in production today made from dry fiber and vacuum infusion – a few examples are shown below. Some of these assemblies, such as flight control surfaces (flaps and ailerons) and fuselage frames are considered secondary or redundant components. Others such as the Aft Pressure Bulkheads of the A380 and 787 are primary structure – failure of these critical components would likely lead to loss of the aircraft. The A400 Cargo Door operates in an even more challenging environment – this flat and large door sees full cabin pressurization, and experiences significant bending and tension loads during flight.
That these highly critical parts are made using these materials and processes speaks to the high degree of confidence that the aircraft OEM’s and regulatory authorities have in the reliability, performance and safety of the dry fiber/infusion approach.
Arguably the most advanced use of dry fibers and infusion is in the wings of next generation airliners such as the Bombardier CSeries and Irkut MS21 aircraft shown below. These aircraft, serving 120 to 200 passengers, are the newest in commercial aviation and have leveraged the latest advances in composite materials, processes and production methods available today. The CSeries has passed ground structural tests and is expected to make its first flight mid 2013, with the MC21 to follow about a year later.
How about your company – is this technology being considered and for what applications? What are the benefits, tradeoffs, concerns and issues associated with the use of these processes? Let us know what you think.