Core Materials & Sandwich Structures Flashcards
7 cards from real CCT practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 7 Core Materials & Sandwich Structures flashcards as text
What is the standard method for sealing exposed honeycomb core edges to prevent moisture ingress in service?
Answer: Filling edge cells with compatible potting compound or applying a fiberglass edge closure strip
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.
What is the typical cell size designation for standard aerospace-grade Nomex honeycomb, and how is it measured?
Answer: Cell size is the distance between parallel cell walls measured across the flat side
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.
When installing a through-bolt insert in a sandwich panel, what is the correct sequence of operations?
Answer: Drill hole → clean → apply primer → fill with potting compound → cure → drill final hole → install fastener
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.
What phenomenon causes the density of a honeycomb core to increase when the core is curved (bent) around a mold?
Answer: Cell wall compression on the inner radius causing cells to buckle and close slightly
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.
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?
Answer: Core flatwise compressive strength and modulus
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.
What is the purpose of an 'insert doubler' or 'insert plate' added to a sandwich panel at a fastener location?
Answer: To spread the fastener bearing load over a larger area of the face sheet and core, reducing local stress
An insert doubler is a local reinforcement that distributes concentrated fastener loads over a larger panel area, preventing face sheet bearing failure and core crushing at the attachment point.
What is the correct storage condition for unexpanded (block form) or pre-expanded Nomex honeycomb core to maintain its properties before fabrication?
Answer: Store in a dry, controlled-humidity environment per manufacturer specification, typically below 50% RH
Nomex honeycomb should be stored in a dry environment with controlled relative humidity to prevent moisture absorption, which can degrade adhesive bond quality and introduce voids during cure.