CCT Core Materials & Sandwich Structures 3

Question 1

What is the standard method for sealing exposed honeycomb core edges to prevent moisture ingress in service?

Accepted Answer

Filling edge cells with compatible potting compound or applying a fiberglass edge closure strip

Answer

Exposed honeycomb edge cells must be filled with potting compound or closed with a fiberglass closure strip to prevent moisture migration into the core, which can cause freeze-thaw damage and corrosion.

Question 2

What is the typical cell size designation for standard aerospace-grade Nomex honeycomb, and how is it measured?

Accepted Answer

Cell size is the distance between parallel cell walls measured across the flat side

Answer

Honeycomb cell size is specified as the inside dimension measured across the flat face of a hexagonal cell (e.g., 1/8 inch, 3/16 inch), affecting core density and mechanical properties.

Question 3

When installing a through-bolt insert in a sandwich panel, what is the correct sequence of operations?

Accepted Answer

Drill hole → clean → apply primer → fill with potting compound → cure → drill final hole → install fastener

Answer

The correct sequence ensures the potting compound fully fills the core cells and cures before the final hole is drilled to the fastener diameter, giving maximum pull-out strength.

Question 4

What phenomenon causes the density of a honeycomb core to increase when the core is curved (bent) around a mold?

Accepted Answer

Cell wall compression on the inner radius causing cells to buckle and close slightly

Answer

When honeycomb is bent, the cells on the inner radius are compressed and the outer cells expand, effectively increasing the number of cell walls per unit volume on the inner radius and increasing local density.

Question 5

Which core material property is most critical to evaluate when designing a sandwich panel for compressive out-of-plane loads such as bearing on a floor panel?

Accepted Answer

Core flatwise compressive strength and modulus

Answer

Flatwise compressive strength and modulus resist crushing loads applied perpendicular to the face sheets, which is the primary load case for floor panels and compression-loaded structures.

CCT - Certified Composite Technician Practice Test

CCT - Certified Composite Technician Practice Test

CCT Core Materials & Sandwich Structures 3