Without Boundaries

Composite Materials

When custom coater/laminator Lamart Corp. was chosen by NASA to develop a material for use as the “envelope” of an unmanned space vehicle, Philip Faria, manager of process engineering, and Lee Smith, project manager, recalled the philosophy of company founder Walter Hirsh: “To be truly successful, a company has to challenge itself to find the limits of its capabilities and then create processes and equipment to exceed the old boundaries.”

“Simple but effective,” says Faria, and certainly appropriate for this project.

The unmanned space vehicle, called an Aerobot, will be flown around Titan, a moon of Saturn. The Aerobot will be a lighter-than-air blimp that will fly at a much lower altitude than a satellite during a mission expected to last for up to six months. Lamart is working with NASA on the project at NASA’s Jet Propulsion Laboratory (JPL) in Pasadena, CA.

Taking on the Tough jobs
Difficult projects are nothing new for Lamart. During the Vietnam War, Lamart was awarded a major contract from the government to laminate silk fabric to film for a container bag used for mortar shell propellant. The company also worked on flame-retardant aircraft insulation film and developed a special film-laminated sailcloth used by windsurfers and yachts competing in the America’s Cup races.

Lamart also has worked with NASA in the past, developing a heat-reflective component in America’s first space suit. In recent years, Lamart has placed greater and greater emphasis on applications involving ultra-light composite materials. Applications include the production of millions of square yards of product in the wire, cable, graphic arts, aerospace, and converting industries.

Even with Lamart’s long history of converting ultra-thin-gauge films, the challenges of the Titan project are unique. Unlike typical assignments that call for laminating films with gauges ranging upward from 0.00025 in., Lamart now is working with gauges of 0.00008 in. downward in thickness.

To point out the difficulties of the Titan project, Faria and Smith report this “blimp-like craft” must travel folded within a capsule for about seven years through hostile space, then drop through an atmosphere at an incredible rate of speed, deploy itself and inflate while falling, and not leak after all of this stress. And by the way, the laminate will need to operate at temperatures low enough to liquefy methane!

How It’s Done
With these requirements in mind, Lamart first had to look at transporting the web through the coater without stress (the equipment is proprietary and has been modified in-house). Next, the company had to apply the coating in a way that would ensure the coat weight could be controlled accurately and would be free of pinholes.

Transporting the coated web through a dryer follows, with the film actually floating on an air current for a period of time. This makes it important to gain control of air flow and heat within the dryer.

In dealing with ultra-thin-gauge films so often over the years, Lamart has designed dryers to control both air flow and heat, as well as avoid excessive flutter and distortion of the films. During the lamination phase of the work, Smith and Faria explain, the films should not be stressed any more than necessary. Low-temperature adhesives were specified to minimize thermal expansion of the materials.

Nip pressures were controlled accurately to avoid web distortion, and dwell time was maximized to allow for maximum adhesive flow.

One other element that makes the process so challenging is that the film composite is six layers thick, which requires multiple passes through the equipment. This means any unseen defects or stress in the initial pass becomes magnified in subsequent passes.

Some Special Help
Helping Lamart process the ultra-thin-gauge films for this project is some very specialized equipment, including corona treaters from Pillar Technologies and specialty rubber rolls and compounds from ABBA Rubber that help reduce static. Specialty coating rollers are provided by Interflex Laser Engravers and Passaic Engraving Co.

In order to obtain adequate strength to form a lightweight inflatable, Lamart had to laminate a fabric to the multi-layer film composite. The challenge here was to find a fabric with the right combination of fibers that adhesives would bond to, yet could remain flexible within specific parameters.

JPL tested the entire laminate using a Gelbo Tester from IDM Instruments, a device that twists the construction while immersed in liquid nitrogen. The mode of failure is delamination, or cracks through the composite, which would result in gas leakage and deflation of the inflatable.

According to Faria and Smith, Lamart continues to work on improving the flex performance of the Titan envelope material. To this end, it will employ exotic fabrics made with ultra-fine yarns to improve the strength of the composite. These are fibers generally used for heavier applications, such as ballistic armor, sailcloth, and other areas.

Alternate candidates for films and adhesives still are being considered, but Lamart says remaining work will focus on optimizing the details of the adhesive quantity, processing, and fabric finishing.

Moving On and Out
Following completion of this test program, Lamart will work with a subcontractor, Global Solutions and Scientific Learning (GSSL), Tillamook, OR, to test candidate seam bonding adhesives and techniques and to produce Aerobot for a test flight on Earth.

When Walter Hirsh talked about exceeding old boundaries, he could not have known just how far his company would go. Taking on the Titan project meant boundaries of time (Aerobot is not expected to reach its destination for at least seven years), boundaries of space, and boundaries of technology, every one a challenge for Lamart to meet—and exceed.



CONVERTER INFO:
Lamart Corp.

Box 1648
Clifton, NJ 07015
973/772-6262; lamartcorp.com

SUPPLIER INFO:
Pillar Technologies—pillartech.com
ABBA Rubber Intl.—abbarubber.com
Interflex Laser Engravers—laserengrave.com
Passaic Engraving Co.—passaicengraving.com
IDM Instruments— idminstruments.com.au



Subscribe to PFFC's EClips Newsletter