VARTM process improves missile fabrication
16 Mar 2001
Lockheed Martin Space Systems operations Advanced Technology Centre, working with the structural design engineers from the US Fleet Ballistic Missile (FBM) program, has successfully demonstrated a low-cost, vacuum-assisted resin transfer moulding (VARTM) process to manufacture a large, complex structure integral to the TRIDENT II D5 fleet ballistic missile.
The VARTM project began in 1996 and is one of several independent research and development (IRAD) technology evaluation projects conducted since 1994 to demonstrate advanced material, designs and manufacturing methods and technologies that may significantly reduce the cost of components for future generations of submarine launched ballistic missile (SLBM).
The large structure fabricated to demonstrate the technology was derived from a one-quarter section of the D5 equipment section, consolidating multiple major graphite/epoxy composite parts and forged metal fittings, numerous clips and metallic stiffeners, and thousands of fasteners using integral structural design concepts and VARTM manufacturing methods. The equipment section is said to account for more than half of the total structure cost of the D5 missile.
Compared to traditional aerospace composite fabrication methods, the VARTM process is said to allow integration of parts and can be cured 'out-of-autoclave' as a single component.
The VARTM demonstration article reduced the part count from 61 to one and eliminated more than 376 fasteners. The corresponding manufacturing costs were reduced by approximately 75 percent while maintaining the structure's weight and achieving higher structural efficiency.
The project reportedly demonstrated various infusion techniques to assure uniform resin flow, penetration and distribution, even in complex geometry. Material testing of coupons showed mechanical properties similar to those produced using the conventional autoclave method.
The one-quarter equipment section is one of the largest and most complex composite components ever produced using the VARTM manufacturing method.
'This VARTM demonstration is a major step forward in advancing the producibility of large, complex-shaped, high-performance, integral composite structures,'' commented Allan Chan, manager, FBM Mechanical Product Support.
