Japanese supplier Nippi is looking to reduce the cost of making carbon-fiber composite parts by half, with the anticipated upgrade or successor to the U.S. manufacturer’s 777 a possible early application of this new process.
By eliminating fasteners in complex pieces, Nippi estimates it can also reduce the mass of the parts by 10%.
The company’s process is a form of vacuum-assisted resin transfer molding (Vartm), which Nippi, like other composites makers, is developing as a replacement for the traditional method of using autoclaves to infuse and cure the resin of composites. Also like other manufacturers, it cannot apply the technology and get it certified until an airframe builder, such as Boeing or, chooses it for a new program.
A Nippi executive says the best immediate prospect is a 777 upgrade or successor. Boeing has not launched such a program, but says it is studying the launch of a new widebody around the end of the decade. Separately, Vartm parts already are going into production for Mitsubishi Aircraft’sregional jet with airframe builder supplying fixed tail surfaces made of Vartm composite.
After five years of development, Nippi says it can make the Vartm parts at 30% less cost than parts cured in an autoclave and is offering the process on that basis, says the executive.
Development work is continuing with the aim of reducing by 50% the cost of autoclave composites, with the focuses on making inspections cheaper. Inspection can be done with ultrasound or X-rays, but because of the difficulty of looking into corners, the sensor must be operated manually near joints.
The parts are formed by laying carbon fiber in a tool and sucking in the resin. The tool with wet carbon fiber then goes into an unpressurized oven for a day to cure the resin. Even for complex shapes this is done in one step; there is no partial curing of components before assembly and final curing because the tool can be quite complex in shape. That also means fasteners can be eliminated. The tool and part can be of any size, according to Nippi managers.
Like other Vartm processes, Nippi’s aims to cut costs by eliminating the purchase and maintenance expense of an autoclave and by reducing energy consumption. Materials are a little cheaper, too, one executive says.
Autoclaves use pressure to force resin into the fibers as well as applying the heat needed for curing. A challenge with Vartm is to get the resin thoroughly and evenly infused among the fibers, but Nippi says it is not experiencing this issue.
The company on Oct. 9 displayed a full-scale sample of a Vartm flap at the Japan International Aerospace Exhibition, along with a sample of a Vartm spoiler part that also featured another technology, a foam core. The foam-core concept resembles a surfboard, with the load-bearing material—the carbon fiber composite—held apart by foam, which provides only a little contribution to strength.
A weight reduction of 23% is claimed, but the cost is a little higher. Conventionally, a honeycomb material is used as a spacer in such parts.
The foam-core process is still under development.