Motivation

• Protect Radio Frequency (RF) equipment from external loads
• Built-in RF functionality to receive and block various signals

• Frequency Selective Surfaces (FSS) are used to select what frequency band passes through the radome through use of conductive patches.

Materials and Fabrication

• Copper patches made via etching representing various amounts spacing and patch size

• FSS layers were bonded during cure within the prepreg using autoclave processing

Testing

Application focuses on sandwich structure radomes featuring an FSS within the face sheets.

Test Methods Required for Sandwich Design
• Bending loads
• Tension (ASTM D3039)
• Compression (ASTM D2344)

Results

No reduction in tensile strength.
• Embedded un-etched and etched Pyralux™ compared to composite baseline.
• Failure occurred independent of the embedded layer
• 2 layer samples tested after 8 layer samples exhibited failure near grips

No reduction in compressive strength.
• Failure loads for FSS occurred within standard deviation of baseline composite

Conclusions

For this material and system there was no reduction in tensile or compressive strength. Failure tracked bonding quality.
• Cohesive Bonding (resin/resin)
• Adhesive Bonding (resin/FSS layer)
Baseline, FSS, and Pyralux™ samples failed cohesively representing good bonding

Future Work

Further work requires an in-depth study on FSS layer interaction and the complete sandwich
• Bonding tests (Floating Roller Peel, Shear)
• Sandwich Bending Testing

Acknowledgements

Research was sponsored by the Office of Naval Research under Grant Number N00014-10-1-0325
Mark Mirotznik, CCM Staff, Fineline Circuits, Tencate

Authors: Ray McCauley, Peter Pa, Shridhar Yarlagadda, Michael Keefe