Novel shield designs to protect aircraft against engine fragments An EU initiative investigated new design concepts to protect future aircraft from damage caused by engine component failure. Transport and Mobility Industrial Technologies © kropic, Thinkstock Composite materials are providing a much better strength-to-weight ratio compared to conventional materials, and are widely used in producing many aircraft components. With EU funding, the IMPTEST (Impact test campaign) project aimed at developing protective shields made of polymer composites to protect aircraft from small fragments detached from rotating parts. Project partners studied and tested the impact phenomena of the shielding materials. They used three different impactors at various velocities to determine the ballistic limit velocity for the penetration of metallic shields and three different composite shield concepts. Two design concepts were then selected, followed by a study on the influence that an impact angle has on them. Fibre bundles were tested at ranges from 40 to 120 degrees Celsius. Results were used in impact simulations to study the influence of temperature. Scientists used high-speed photography to document the impact responses of all specimens. They also employed fractographic methods and 3D scanning of the deformed shape after impact to characterise the damage caused to the specimens. Overall, findings reveal that the composite shields with polymer fibres had a penetration threshold velocity per unit weight which was two to three times higher than conventional metal shields. These shields facilitate the use of open rotor engines mounted on rear aircraft fuselage, with the reduced weight contributing to declines in fuel consumption and harmful emissions. Composite shields with glass fibres and metal shields had a similar performance. Shields with ultra-high molecular weight polyethylene fibres performed better than those with aramid fibres. IMPTEST's validated lightweight polymer composite shields will serve as a basis for current and future aircraft development. Such innovative technology is necessary for delivering advanced engine technologies such as the open rotor architecture that can cut fuel emissions and carbon dioxide emissions. Keywords Engine fragments, IMPTEST, protective shields, polymer composite shields
