A simplified test methodology for crashworthiness evaluation of aircraft seat cushions

Abstract

The main subsystems of an aircraft involved in crashworthiness are the seat cushion, which is part of the seat structure, as well as the restraints, fuselage, and landing gear. A crashworthy structure is designed so that in the event of a crash, it will absorb impact energy in a controlled manner. All energy absorption materials such as honeycombs, polyurethane foams, polymer foams, metallic foams, etc. are being used in aircraft structures, to ensure a safe and survivable trip for passengers, and even in packaging applications for sensitive instruments, equipment, and computers. Polyurethane foams are being used for acoustic purposes, as padding in the finished interior panels of the aircraft, and seat cushions, but they are primarily used in seating applications. The fact that a direct interaction exists between the occupant's body and the seat cushion means that the seat cushion must be ergonomically comfortable in addition to providing safety for passengers. All seat cushions must pass Federal Aviation Administration regulations prior to installation. These regulations require a dynamic sled test of the entire seat system in order to certify it. This traditional testing is also required for replacing old, deteriorated cushions with new buildup cushions, which is time-consuming and costly. Much effort has been taken to obtain reliable modeling in terms of substituting dynamic full-scale sled testing with a cheaper and simpler method of certification. The Advanced General Aviation Transportation Experiments (AGATE) group has proposed a methodology using quasi-static testing instead of fullscale sled testing. In this study, AGATE methodology was validated with experimental results from full-scale sled testing and quasi-static testing. Rate sensitivity of foams was investigated and a criterion using stress-relaxation testing techniques is proposed. This paper addresses full-scale sled testing and quasi-static testing of aircraft seat cushions. This investigation recommends that full-scale sled testing used for seat cushion certification be replaced with quasi-static testing.