CCT Core Materials & Sandwich Structures

Question 1

What is the primary structural purpose of core material in a sandwich composite panel?

Accepted Answer

Separate face sheets to increase bending stiffness with minimal weight gain

Answer

Increase panel weight for stability

Answer

Provide electrical conductivity between face sheets

Answer

Replace adhesive film between plies

Question 2

Which core material is most commonly used in aerospace structural sandwich panels due to its high strength-to-weight ratio and fire resistance?

Accepted Answer

Nomex aramid honeycomb

Answer

End-grain balsa wood

Answer

PVC closed-cell foam

Answer

Aluminum honeycomb with polyester face sheets

Question 3

What is the term for the failure mode in a sandwich panel where the face sheet buckles locally due to insufficient core support?

Accepted Answer

Face sheet wrinkling

Answer

Delamination

Answer

Core shear failure

Answer

Interlaminar tension failure

Question 4

What is the 'ribbon direction' of honeycomb core, and why does it matter?

Accepted Answer

The direction in which cells are aligned and bonded; it has the highest shear modulus

Answer

The direction perpendicular to cell walls; it has no structural significance

Answer

The direction of resin flow during infusion; it determines permeability

Answer

The direction of autoclave pressure application; it governs cure quality

Question 5

What is the purpose of 'potting compound' used around inserts in composite sandwich panels?

Accepted Answer

To locally fill and solidify the core to distribute insert loads and prevent crushing

Answer

To seal panel edges from moisture ingress

Answer

To bond face sheets to the core during secondary bonding

Answer

To provide electrical grounding for the panel

Question 6

Which non-destructive testing (NDT) method is most commonly used to detect disbonds between the face sheet and core in a sandwich structure?

Accepted Answer

Coin tap testing or ultrasonic through-transmission

Answer

Radiography (X-ray)

Answer

Eddy current inspection

Answer

Dye penetrant inspection

Question 7

When splicing honeycomb core panels edge-to-edge, what material is typically used to fill the joint and restore continuity?

Accepted Answer

Syntactic foam or potting compound filled into the gap

Answer

Dry woven fiberglass tape

Answer

Film adhesive strips only

Answer

Additional layers of prepreg