Composite Aerospace Structures Questions and Answers

Answer: C

Correct answer: It cannot compute the in-plane stiffness of a laminate

Computing the in-plane stiffness is exactly what classical laminate theory does best - the A matrix is its principal output and it is reliable. The other three are genuine limitations: no free-edge interlaminar stresses, an assumed perfect bond between plies, and plane stress in each ply, the last of which is the source of the first.

Answer: D

Choosing the layup determines the material's properties, so the designer creates the material and the part in one act. That freedom is the source of both the weight saving and the added complexity in analysis, manufacture, inspection and repair.

Answer: A

Where a large area must be held stiff at minimum weight, separating thin composite faces with a light core is extremely efficient. Concentrated axial loads and hard points are better carried by solid laminate or by metal fittings.

Answer: B

A thermoplastic softens on heating rather than curing irreversibly, which allows welding, reforming and rapid processing. Higher processing temperatures and greater melt viscosity are the trade, along with a shorter service history in primary structure.

Answer: C

A fuselage barrel needs a very large pressure vessel, and the capital and cycle costs are considerable. Vacuum-bag-only materials aim for comparable void content without the vessel, though matching autoclave quality remains demanding.

Answer: D

The faces give \( 2 \times 0.001 \times 1560 = 3.12 \) and the core \( 0.020 \times 50 = 1.0 \), totalling \( 4.12 \) kg/m\( ^2 \). The core adds a quarter of the mass while multiplying the bending stiffness many times over.

Answer: A

Both are true and the second explains the first. Fusion bonding avoids both fasteners and adhesives, which is a significant attraction, though the higher processing temperatures and limited service history have slowed adoption in primary structure.

Answer: B

Correct answer: 1 and 2 only

Statements 1 and 2 are correct: separating thin stiff faces with a light core raises the second moment of area enormously for little added weight, and the core is a small fraction of the mass. Statement 3 is wrong - a sandwich is poor at taking a concentrated axial load, since the core cannot carry it and the faces will wrinkle or the core crush, so hard points need a solid laminate insert.

Answer: C

Correct answer: Autoclave-cured parts are structurally inferior

Autoclave cure produces the best consolidation and the lowest void content available, so the parts are the standard against which others are judged, not inferior to them. The reasons for pursuing out-of-autoclave routes are all practical: the capital cost of the vessel, the cycle time it imposes on throughput, and the impossibility of building a pressure vessel large enough for the largest parts.

Answer: D

Yield, buckling, crippling, fatigue, fracture, delamination and joint failure each carry their own allowable, and the lowest governs. Identifying which that is for every member, and demonstrating a positive margin against it, is the whole of the discipline.