CCT Core Materials & Sandwich Structures 2

Question 1

What is the main advantage of end-grain balsa wood core compared to closed-cell foam cores in marine composite applications?

Accepted Answer

Excellent compressive strength and stiffness at relatively low cost

Answer

Higher temperature resistance up to 300°F

Answer

Resistance to water absorption without any sealing

Answer

Lower density than all foam alternatives

Question 2

What foam core type offers the best performance in applications exposed to elevated temperatures above 250°F (121°C)?

Accepted Answer

PMI (polymethacrylimide) foam such as Rohacell

Answer

PVC (polyvinyl chloride) cross-linked foam

Answer

SAN (styrene acrylonitrile) foam

Answer

EPS (expanded polystyrene) foam

Question 3

Which process is used to form flat honeycomb core into a curved shape without cutting and re-bonding?

Accepted Answer

Flex-core expansion or OML machining

Answer

Resin transfer molding

Answer

Wet layup reshaping at room temperature

Answer

Compression molding with matched tooling

Question 4

What structural failure occurs when the core itself fails in shear under out-of-plane loading in a sandwich panel?

Accepted Answer

Core shear failure

Answer

Face sheet delamination

Answer

Panel buckling

Answer

Adhesive peel failure

Question 5

Why must foam core materials be properly vented or perforated before autoclave processing?

Accepted Answer

To prevent trapped air or volatiles from expanding and causing face sheet disbonds or blistering

Answer

To allow resin to flow into the core cells for better bonding

Answer

To reduce the overall weight of the panel by removing foam material

Answer

To allow thermocouple wires to pass through the panel

Question 6

What is the correct terminology for the tapered transition at the edge of a sandwich panel where the core thickness is gradually reduced to zero?

Accepted Answer

Core runout or core ramp

Answer

Ply drop-off

Answer

Scarfed edge

Answer

Edge band

Question 7

What is the minimum recommended film adhesive weight (per square foot) typically used to bond honeycomb core to prepreg face sheets in aerospace applications?

Accepted Answer

0.03 to 0.06 psf (0.15 to 0.30 kg/m²)

Answer

0.01 psf (0.05 kg/m²)

Answer

0.15 psf (0.73 kg/m²)

Answer

0.50 psf (2.44 kg/m²)