Boron/epoxy tapes

Boron-Epoxy Prepreg Tape (Courtesy of General Dynamics)... 

Key boron/tungsten iiber reinforced epoxy tapes are used in the aerospace market in selected applications on the F-14 and F-15 fighters, the B-1 bomber, the Blackhawk series Sea Stallion... 

Boron fibers have also been used in the form of epoxy prepreg tapes in which the filaments are carefully aligned and tensioned to provide a one-fllament-thick tape. Generally, these tapes are composed of 65-70 percent filaments in the epoxy resin matrix. The longitudinal flexural modulus of boron-epoxy laminates made in this way is about 27 X 10 psi, and the flexural strength is 280,000 psi. Boron fibers have also been applied to reinforce epoxy novolacs, phenolics, and polyimides in laminate construction. 

Applications. Boron fibers are used as unidirectional reinforcement for epoxy composites in the form of preimpregnated tape. The material is used extensively, mostly in fixed and rotary wing military aircrafts for horizontal and vertical stabilizers, mdders, longerons, wing doublers, and rotors. They are also used in sporting goods. Another application is as reinforcement for metal matrix composites, in the form of an array of fibers pressed between metal foils, the metal being aluminum in most applications. 

It is not necessary to dwell on the properties of boron that make it attractive, especially in prepreg tape form, for both filament-wound and laid-up structures. Table III compares boron with both S-glass and Thomel 5-S in epoxy composite form. The numbers shown are typical for uniaxial specimens at about 60 vol % fiber. Specific points worthy of mention for their merit, or lack thereof, are... 

Fibre production began in 1972 at 100000 Ib/annum with plans to increase as the market develops. Large price reductions for the fibre were timed by Du Pont to coincide with the 1972 Farnborough air show bringing epoxy pre-preg fabric for instance down to 20-30 per lb, and projected costs are expected to be lower than for carbon and boron fibres. It has been reported that the fibre will be availaWe as collimated tape, chopped fibre, yams, rovings and as woven fabric. ... 

These adhesives consist of a polymerizable liquid matrix and large volume fractions -of electrically insulating thermally conductive filler. Typical matrix materials are epoxies, silicones, urethanes, and acrylates, although solvent-based systems, hot-melt adhesives, and pressure-sensitive adhesive tapes are also available. Aluminum oxide, boron nitride, zinc oxide, and increasingly aluminum nitride are used as fillers for these types of adhesives. The filler loading can be as high as 70 - 80 wt %, and the fillers raise the thermal conductivity of the base matrix from 0.17-0.3 up to about... 

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