SEDL / STP / STP1383-EB / STP14505S

Parametric Study of Three-Stringer Panel Compression-After-lmpact Strength

Rousseau, CQ
Principal engineer and senior engineering specialist, Bell Helicopter Textron Inc., Fort Worth, TX

Baker, DJ
Research scientist, USA ARL/VTD, NASA Langley Research Center, Hampton, VA

Hethcock, JD
Principal engineer and senior engineering specialist, Bell Helicopter Textron Inc., Fort Worth, TX

Pages: 33    Published: Jan 2001

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Abstract

Damage tolerance requirements for integrally stiffened composite wing skins are typically met using design allowables generated by testing impact-damaged subcomponents, such as three-stringer stiffened panels. To improve these structures, it is necessary to evaluate the critical design parameters associated with three-stringer stiffened-panel compressive behavior. During recent research and development programs, four structural parameters were identified as sources for strength variation: (a) material system, (b) stringer configuration, (c) skin layup, and (d) form of axial reinforcement (tape versus pultruded carbon rods). The relative effects of these parameters on damage resistance and damage tolerance were evaluated numerically and experimentally. Material system and geometric configuration had the largest influence on damage resistance; location and extent of the damage zone influenced the sublaminate buckling behavior, failure initiation site, and compressive ultimate strength. A practical global-local modeling technique captured observed experimental behavior and has the potential to identify critical damage sites and estimate failure loads prior to testing. More careful consideration should be given to accurate simulation of boundary conditions in numerical and experimental studies.