NetComposites
Thermwood

New Reinforced Foam Core material

29 November 2001

At the US Fall SAMPE in Washington Aztex and Sikorsky gave a joint paper on their program to produce a lightweight, more damage tolerant alternative to Nomex® honeycomb. The development program has targeted the US Army’s RAH-66 Comanche helicopter.

The new core material is a reinforced foam core that uses thin diameter pultruded pins inserted into a lightweight foam carrier for structural performance. The pins are arranged in a truss configuration for structural integrity. The pins are inserted into the foam using a highly automated process which leads inherently to a low cost product with very little scrap. In production, which will start early in 2002, the core material will be sold as finished core assemblies/details Ramped edges, formed contour, local densification, etc.) as opposed to flat sheet stock. This will be possible because a simple, completely automated process is used to fabricate the new core material. The process will utilize 3-D engineering electronic data generated during the part design by the customer. This data is converted into NC machine code that fully defines the core features. This approach eliminates operator sensitivity and variability typically associated with honeycomb core details. In addition automation allows for easy tailoring of individual core details to meet specific engineering requirements.

This simple fabrication approach gives the composite engineer many degrees of freedom to design an optimal low cost core structure. By varying pin materials, pin diameters, pin lengths, pin angles, pin density and foam materials the design engineer can create the optimal core product for any given design without the constraints of traditional honeycomb or foam materials. Sandwich structures from this new material can be processed utilizing traditional composite fabrication processes (fabric and tape hand lay-up) as well as newer low cost processes such as fiber placement. In addition initial development work has indicated that the new core material can also be successfully processed using resin transfer molding, (RTM) and vacuum assisted (VARTM) processing.

Sikorsky Aircraft have been evaluating this material for rotorcraft applications over the last 2 years under a cooperative agreement with the Aviation Applied Technology Directorate (ATTD), US Army Aviation and Missile Command titled “Rotary Wing Structures Technology Demonstration (RWSTD) program”. The work so far has developed material properties and producibility guidelines for the insertion of this new material into aircraft applications such as the Army’s RAH-66, Comanche helicopter.

In addition to demonstrating mechanical equivalency to Nomex materials at least 10% weight savings have been shown with improved damage tolerance. For further Information contact Tony Bonnington President Aztex Inc