Composite Aerospace Structures Questions and Answers

Answer: C

Extension-bending coupling makes an unsymmetric laminate distort as it cools and again as it is loaded, neither of which a skin holding an aerodynamic contour can tolerate. Symmetry is essentially mandatory for such a part.

Answer: D

A composite is essentially elastic to failure, so the peak predicted by an elastic analysis is what the joint actually sees. Edge distance and hole quality both matter a great deal, the latter because drilling can delaminate the laminate at the exit face.

Answer: A

Correct answer: It principally reduces the fibre-dominated tensile strength

This is the false statement. Moisture and heat act on the polymer matrix, so what they degrade are the matrix-dominated properties - compression, in-plane and interlaminar shear, and bearing. Longitudinal tensile strength, carried by the fibres, is largely unaffected, which is why the hot-wet case rarely governs a tension-critical member.

Answer: B

Correct answer: Magnetic particle inspection

Magnetic particle inspection relies on a magnetic field leaking at a discontinuity, so it works only on ferromagnetic materials. Carbon composite is not ferromagnetic and the method detects nothing. The other three are all standard: ultrasonic inspection for delaminations, thermography for larger areas, and tap testing as a quick manual check.

Answer: C

Carbon is conductive and noble relative to aluminium, so with any moisture present the aluminium corrodes preferentially. A glass fibre interleaf or sealant is required, and titanium fasteners alone address only the fastener interface.

Answer: D

Correct answer: Composite structures are heavier than metal ones

This is not true and would not be a reason for testing in any case - composite structures are chosen precisely because they are lighter. The genuine reasons are the other three: failure modes that resist first-principles prediction, properties that vary with process and environment, and impact damage effects that can only be established empirically.

Answer: A

Correct answer: It occurs at ply interfaces

Delamination is the separation of adjacent plies, occurring at the resin-rich interface between them where no fibre crosses. Fibres are not broken, which is why the damage can be extensive without any surface indication. It arises under interlaminar tension or shear, and impact is the commonest cause - not tension in the plane of the laminate.

Answer: B

An external patch is quicker and needs less process control, but the load path steps out and back, producing bending and a concentration at the patch edge. Scarfing tapers the transition through the thickness and is used where structural efficiency matters.

Answer: C

Each ply's stiffness is rotated into the laminate coordinate system and integrated through the thickness, producing the A, B and D matrices. It assumes a perfect bond and plane sections remaining plane, and it says nothing about interlaminar stresses.

Answer: D

Maximum stress checks each direction independently, whereas Tsai-Wu combines them into one quadratic that accounts for interaction between the stress components. It fits data better but does not identify which mode caused failure.