AIRCRAFT ENGINE FRAGMENT BARRIERS

SRI International is performing research under contract to FAA to protect critical aircraft components against fragments resulting from uncontained failure of a turbine engine. The following reports in PDF format are available from this research:

• "Lightweight Fragment Barriers for Commercial Aircraft" presented at the 18th International Symposium on Ballistics, San Antonio, Texas (November 1999) [680 Kb]. The ballistic resistance of woven high-strength polymer fabrics to aircraft engine fragments was evaluated. Gas gun tests were performed to determine the relative effectiveness of Kevlar, Spectra, and Zylon and the effect on ballistic performance of fragment sharpness, fabric gripping conditions, and fabric areal density. A computational fabric model was constructed based on yarn geometry and properties and weave configuration. The model was implemented in LS-DYNA3D to simulate impact tests and elucidate the effect of yarn density and fabric gripping conditions. Full-scale tests on an aircraft fuselage section showed that a few plies of Zylon fabric glued to the insulation package within the fuselage wall.

• "Full-Scale Tests of Lightweight Fragment Barriers on Commercial Aircraft", SRI Semiannual Report No.6 to FAA, (July 1999) [600Kb]. SRI performed full-scale fabric barrier tests on an aircraft fuselage at the Navy Air Warfare Center in China Lake, CA. The tests examined the effects of polymer material, number of plies, location of the fabric within the fuselage wall, and gripping arrangements.

• "Improved Barriers to Turbine Engine Fragments: Interim Report I," DOT/FAA/AR-99/8, I, (June 1999) [10.0 Mb]. The ballistic performance of various barriers of Zylon (polybenzoxazole, PBO) fabric was measured in gas gun tests using fragment simulating projectiles. Failure mechanisms and effects of multiple fabric plies and gripping mode were investigated. Absorbed kinetic energy appears to increase linearly with fabric areal density. It was found that a layer of fabric glued to the interior wall panel absorbed considerable energy at very low added weight. To assist in model development, quasi-static penetration tests were performed with a tensile machine in conjunction with a video camera to elucidate the phenomenology and evolution of fabric failure. Tensile properties of Zylon yarn were measured at several strain rates. The framework of a fabric model was constructed and simple impacts were simulated to demonstrate efficacy.
• "Improved Barriers to Turbine Engine Fragments: Interim Report II," DOT/FAA/AR-99/8, II, (May 1999) [1.2 Mb]. Several numerical problems were solved associated with modeling the crimped geometry and interaction of woven yarns. The model behaved properly in simple simulations of single yarn response to axial and transverse loads. Laboratory and field site tests were performed to provide data for developing and validating the computational model. The ballistic response of fabrics to fragment impact was evaluated, the phenomenology of fabric deformation and failure was elucidated in quasi-static penetration tests, and the tensile properties of yarns and fibers were measured. Three high-strength polymer materials were examined: PBO (Zylon), aramid (Kevlar), and polyethylene (Spectra).