“The acoustic benefits are very interesting because they are achieved with very little additional weight to the sandwich construction,” Lowry says. “This offers the potential to reduce weight in the aircraft by replacing some or all of the heavier conventional means of managing sound.”

Today, honeycomb with GillFISTS can be processed in a vacuum bag, autoclave or conventional press. Foam density is a function of the coating formulation and can be tailored over a broad range of densities, Lowry says. Because whole blocks are subject to the process and the foam generates in-situ, the bonding of the facing is relatively unaffected. Also, he says, it is possible to produce machined core parts with GillFISTS and selectively coat sections of the core if a customer has a unique application.

A New Sealant for Foam Cores

3A Composites, a material supplier based in Cham, Switzerland, has more than 50 years of experience manufacturing structural core materials (such as closed cell foams) and balsa products. It recently sought a way to reduce the amount of resin absorbed by foam, which in effect would lower the weight and cost of making composite sandwich parts in resin infusion processes.

Decision-makers in the marine, wind energy, industrial markets and others often prefer PET (polyethylene terephthalate) foam cores because the material is easy to use and can produce composite parts with a high level of consistency, says Philipp Angst, director of product management at 3A Composites Core Materials. “Currently, the major problem with PET is that the resin uptake is higher than comparable polyvinyl chloride (PVC) foam, which limits its cost advantage in infusion applications.”

Motivated to ease the problems associated with resin uptake, 3A Composites began developing technology to give its PET foam, AIREX T92, an advantage over competitive core materials like styrene acrylonitrile (SAN) or PVC. It developed a new surface sealant for PET foam cores called AIREX SealX.

“We can now reduce the resin taken up by the core’s surfaces during infusion processes by about 50 percent,” says Marc Anderson, director of sales and marketing at Baltek Inc., a subsidiary of 3A Composites. “The reduction in resin will reduce overall weight and fabrication costs of the end product – two targets that are very high priorities for our customers.”

Researchers at 3A Composites had to overcome several obstacles to create SealX, including finding the optimal balance between minimum resin uptake and good core-skin adhesion, Angst says. The company says SealX reduces resin uptake in balsa core by approximately 80 percent and composite weight by 35 percent, and it predicts that the new balsa surface sealant could significantly curb the weight and cost of balsa sandwich panels.