SBIR-STTR Award

Sandwich core structures represent a lightweight and structurally efficient approach for composite airframe fabrication. However, the use of sandwich core structures has also presented many challenges, particularly for Navy aircraft that tend to see extensive exposure to salt spray and high humidity environments. In these environments, any defect or damage to the sandwich facesheets allows moisture intrusion into the cells of the honeycomb. Once this process has begun, the result is almost inevitable – corrosion of the metallic components and delamination of the facesheets from the core. Aztex has developed a technology that utilizes a lightweight, closed cell foam as a base. The foam is then reinforced with very small diameter pultruded rods. This technology provides a means to utilize a closed cell foam core with relatively poor mechanical properties and by the addition of Z-Fiber™ rods, create a high strength, damage tolerant core structure with the potential for strengths comparable to aluminum honeycomb. In this program, Aztex proposes to utilize our K-Cor™ product as a basis to develop a replacement core material for aircraft control surfaces, focusing on the F-14. This technology would be applicable to other existing or future aircraft applications.

Benefits:
Aztex has developed a technology that utilizes a lightweight, closed cell foam as a base. The foam is then reinforced with very small diameter pultruded rods. This technology provides a means to utilize a closed cell foam core with relatively poor mechanical properties and by the addition of Z-Fiber™ rods, create a high strength, damage tolerant core structure with the potential for strengths comparable to aluminum honeycomb, excellent damage tolerance and resistance to moisture intrusion. An alternative to conventional honeycomb materials without the inherent problems associated with honeycomb cores has potential applications in both military and commercial aerospace applications. In addition, there are many non-aerospace uses such as railway floor panels, truck bodies, Formula 1 cars, etc. Our research indicates that the market potential for commercial applications for this technology (both aerospace and non-aerospace) exceeds $50M/year.

Keywords:
Sandwich, X-Cor (tm), Damage Tolerance, F-14, Honeycomb, K-Cor (tm), Control Surface, EA-6B

Sandwich core structures represent a lightweight and structurally efficient approach for composite airframe fabrication. However, the use of sandwich core structures has also presented challenges, particularly in high humidity environments. In these environments, any defect or damage to the sandwich facesheets allows moisture intrusion into the cells of the honeycomb. A simple approach to address moisture intrusion of conventional honeycomb materials would be to use closed-cell foam, however, the strength properties of foam cores is limited at best. Aztex has developed a technology that utilizes lightweight, closed cell foam as a base. The foam is reinforced with very small diameter pultruded rods (typically carbon fiber/BMI or epoxy). The rods are used to create a truss network in the foam. This approach can be tailored to the specific applications. Shear and compression strengths can be adjusted as required (locally if necessary) to achieve the desired combination of core weight versus mechanical properties. The purpose of this program will be to develop preliminary design allowables and fabricate and test manufacturing demonstration hardware. We have discussed this program with Lockheed Martin Aerospace (Fort Worth, TX) who have agreed to support this Phase II program for application in the F-35 MLG doors. Aztex X-Cor and K-Cor technology represents a completely new class of core materials. These materials can be produced as completed parts, ready for incorporation into the structure without the additional machining, potting and edge filling steps required with conventional honeycomb. X-Cor and K-Cor also can be designed with shear and compression strengths significantly greater than foam cores. Successful completion of this program will provide preliminary design allowables data for X-Cor/K-Cor and strcutural demonstration components as a first step for incorporation of these materials on F-35/JSF. These materials have essentially unlimited applications on DoD and commerical aerospace platforms, commerical aircraft, ground transportation, military shelters, etc. X-Cor and K-Cor can be used in any application where conventional core materials could be used, but without the moisture intrusion issues of honeycomb or the strength limitations of foam cores.

Keywords:
X-Cor, K-Cor, F-35, Jsf, Main Landing Gear Doors, Core, Sandwich Structure