Core Materials & Sandwich Structures Flashcards
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Read the first 7 Core Materials & Sandwich Structures flashcards as text
What is the primary structural purpose of core material in a sandwich composite panel?
Answer: Separate face sheets to increase bending stiffness with minimal weight gain
Core material separates the face sheets, dramatically increasing bending stiffness (I-beam effect) while adding very little weight.
Which core material is most commonly used in aerospace structural sandwich panels due to its high strength-to-weight ratio and fire resistance?
Answer: Nomex aramid honeycomb
Nomex aramid honeycomb offers excellent strength-to-weight ratio, fire resistance, and low moisture absorption, making it the preferred aerospace core.
What is the term for the failure mode in a sandwich panel where the face sheet buckles locally due to insufficient core support?
Answer: Face sheet wrinkling
Face sheet wrinkling is a local buckling mode caused by inadequate core density or thickness failing to support the compressive face sheet.
What is the 'ribbon direction' of honeycomb core, and why does it matter?
Answer: The direction in which cells are aligned and bonded; it has the highest shear modulus
The ribbon direction (L-direction) is where honeycomb cell bonds run, giving the highest shear modulus and strength, so orientation must match design loads.
What is the purpose of 'potting compound' used around inserts in composite sandwich panels?
Answer: To locally fill and solidify the core to distribute insert loads and prevent crushing
Potting compound fills the core cells around hardware inserts to distribute fastener loads over a larger area and prevent honeycomb crushing under pull-out forces.
Which non-destructive testing (NDT) method is most commonly used to detect disbonds between the face sheet and core in a sandwich structure?
Answer: Coin tap testing or ultrasonic through-transmission
Coin tap testing and ultrasonic through-transmission testing are the standard methods for detecting face-to-core disbonds, with tap testing being the simplest field technique.
When splicing honeycomb core panels edge-to-edge, what material is typically used to fill the joint and restore continuity?
Answer: Syntactic foam or potting compound filled into the gap
Syntactic foam or potting compound is used to fill core splice gaps, providing a smooth, solid transition that prevents stress concentrations and moisture trapping.