Material Selection & Properties Flashcards
7 cards from real AM practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 7 Material Selection & Properties flashcards as text
What is exfoliation corrosion and on which aircraft structure type is it most commonly found?
Answer: Layered delamination corrosion in high-strength aluminum extrusions and rolled products
Exfoliation corrosion progresses along grain boundaries parallel to the surface in wrought aluminum products, causing leaf-like delamination visible as blistering.
Which fiber type used in composite aircraft structures offers the highest stiffness (elastic modulus) per unit weight?
Answer: Carbon (graphite) fiber
Carbon fiber has the highest specific stiffness (modulus-to-density ratio) of common aerospace reinforcing fibers, making it preferred for stiffness-critical structures.
What does 'passivation' of stainless steel components involve?
Answer: Immersing in nitric or citric acid solution to remove free iron and enhance the chromium oxide layer
Passivation removes surface iron contamination with an acid bath, allowing chromium to form a dense, continuous oxide layer that resists corrosion.
When specifying a substitute material for an aircraft structural repair, what document governs acceptable substitutions?
Answer: The manufacturer's Structural Repair Manual (SRM) or an approved engineering order
Material substitutions must be authorized by the manufacturer's SRM or an approved engineering order; unapproved substitutions can compromise structural integrity.
What is the primary purpose of anodizing aluminum aircraft parts?
Answer: Create a hard, corrosion-resistant oxide layer and improve paint adhesion
Anodizing electrochemically grows a thick aluminum oxide layer that resists corrosion, improves wear resistance, and provides an excellent base for paint or primers.
Which material defect is described as a thin flat separation or weakness in the interior of a metal, usually aligned with the grain flow?
Answer: Lamination
Laminations are planar discontinuities in wrought metals caused by the rolling or forging of subsurface inclusions or gas pockets into thin, elongated flaws.
Why must composite repair patches typically be tapered (scarfed or stepped) rather than having abrupt edges?
Answer: To distribute load transfer gradually and minimize stress concentrations at patch boundaries
Tapered or stepped patch edges distribute the shear load transfer over a length rather than concentrating it at a single discontinuity, preventing edge delamination.