JEC COMPOSITES MAGAZINE - Issue #73 - June 2012 - 67

Fig. 2: Example of a front-mounted radome for a jet (left), example of a radome (right)

integrity. Applying unidirectional reinforcement tape to fabricate these parts without wrinkles is difficult and time consuming. The new material could allow for more efficient and uniform formation of these parts.

The ability of this discontinuous unitape to form complex parts has drawn the attention of Tom Campbell, applications engineer at Fiberforge, Inc., a Colorado-based technology company that has developed a patented manufacturing process for continuous fibre-reinforced thermoplastic parts. As a leader in thermoplastic advanced composites, this company delivers costeffective solutions for manufacturing high-performance products. It offers manufacturing equipment, production of composite parts and engineering services to meet their client’s needs. Tom Campbell is evaluating a thermoplastic version of the material for possible use in aerospace applications. Fiberforge sees significant potential in the DiscoTape process in forming complex parts from thermoplastic composites. The possibility of discontinuous forming behaviour in a nearly continuous material is very intriguing and the company looks forward to exploring the possibilities and bounds of this new material format. n
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tures must be as close to transparent as possible in allowing radar frequencies to penetrate the structure. A study on the formability and transmissivity of glass DiscoTape, applicable for use in radome manufacture, was completed. Test specimens of discontinuous glass prepreg unitape were formed and Pepin Associates contracted with Radant Technologies of Stow, Massachusetts to measure the electrical properties of these specimens. The team has shown that discontinuity does not always affect transmissivity of the radar signal. It was found that the discontinuity may interfere with the signal at X-band frequencies, depending on material perforation.. In the event the material causes signal loss, the length of unitape segments can be altered easily, allowing the fabricator to “tune” the material as needed. The research showed no appreciable effect on the material transparency for the Q-band frequency. These results are promising because radome shapes are as variable as the aircraft on which they are mounted. The photo in Figure 2 shows an example of a front-mounted radome for military jets (left). Figure 2 (right) shows a more blunt radome, which might be mounted to the underbelly of an aircraft.

It has the potential to be used on many other structures ranging from wind blades to medical imaging equipment to structures for aircraft and rotorcraft. Pepin Associates is seeking to evaluate applications for hard-to-form parts and structures commonly made with continuous unitape. The part shown in Figure 3 is the secondary structure of a modern military rotorcraft, formed with carbon fibre DiscoTape. The forming capabilities of this material should provide a significant manufacturing advantage in terms of time savings and reduction of scrap material versus the use of continuous unitape. There is more development work to be done, but the initial results are very promising.

Technological challenge
Forming such complex curvatures as these with continuous, unidirectional tape is a challenge due to wrinkling of the material. Wrinkles can degrade both the radar signal and radome structural

Fig. 3: Small fairing formed in a vacuum chamber using 3 plies of DiscoTape™ discontinuous unidirectional tape (IM7/8552). The three-ply flat lay-up was preformed in this chamber in less than 30 seconds

No73 June 2012

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JEC COMPOSITES MAGAZINE - Issue #73 - June 2012

Table of Contents for the Digital Edition of JEC COMPOSITES MAGAZINE - Issue #73 - June 2012