As an aircraft or spacecraft ascends, the atmospheric pressure drops. If the internal pressure is not released, a pressure differential develops on the facesheet. With an in-plane load from vehicle acceleration as well, the pressure and in-plane load may cause failure. Vented sandwich structures are strongly preferred since they release the internal pressure; however, special cases still require an unvented design. This paper provides an analysis and test methodology for unvented sandwich structures. Parametric studies of facesheet-core debonding and buckling were conducted via finite element analysis, considering geometric, material, and load parameters. Design curves based on the key nondimensional parameters were tuned to the data from the parametric study, providing a tool to predict facesheet-core debond failure. Examples of how to use the design curves in practical applications are provided.
Impact damage caused by ground vehicles and equipment colliding with the structural components of aircraft is a significant source of damage to commercial aircraft that may go unreported. Most common are blunt impacts from ground maintenance and service vehicles and equipment with attached elastomeric bumpers that protect the aircraft to some degree but may not leave externally visible evidence of an impact. This research examines the types of impact threats to a composite airplane fuselage, impact testing of composite specimens that simulate airplane fuselage specimens, and the visible detectability of the damage. The test program has two distinct aspects: (a) prediction through analysis and (b) small- and large-scale quasistatic indentation testing.
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