FATIGUE BEHAVIOR OF STITCHED STIFFENEDCOMPOSITE PANEL WITH IMPACT DAMAGE

摘要

Textile structural composites with through-the-thickness reinforcement arepromising materials for aircraft structural applications. In this work, the compressive fatiguebehavior of stitched, stiffened panels with clearly visible impact damage (CVFD) on the flangehas been studied experimentally. The panels having two blade stiffeners are composed of 3501-6epoxy resin and AS4-3k plain weave fabrics stitched with Kevlar 2790 yarn. The panels wereimpacted at the flange area before fatigue tests. These impacted panels were tested in constantamplitude compression fatigue loading and modified Transport Wing Standard Test (TWIST)spectrum fatigue loading. In all constant fatigue tests, cracks emanated from the impact site andpropagated towards the stiffener. The stiffener stopped the crack for most of the panel’s fatiguelife. Once the crack penetrated the stiffener, the panel failed within a few cycles. However, underspectrum fatigue loading, the panels could suddenly crash without visible sign of damageevolution.