Composite - Live Class

A: —that's the most common mistake, treating nominal CPT as elastic. It doesn’t grow like that. Run the arithmetic: 32 × 0.125 mm is 4.0 mm, and consolidation reduces, it doesn’t add 0.6 mm. 8552/IM7 cured CPT stays near nominal at 55–60% Vf. ±45 placement doesn’t inflate thickness by 15%. Moisture flashes off. With no shims, the only credible paths are extra plies or a wrong CPT assumption baked into the drawing, both certification issues when the design engineer is gone.

A: —people average CTEs and miss the constraint. The matrix wants to shrink ~50e-6/°C × 160 °C ≈ 0.008, or 0.8%. Fibers pin it. Some relaxes near Tg, but not an order of magnitude. That’s why cool-down cracking shows up even when strength margins look fine.

A: —that’s the trap, chasing the biggest number. Service failures start at BVID, not coupon perfection. CAI exposes delamination growth and fiber microbuckling that pristine compression never sees. Fatigue and cure method aren’t the drivers; damage tolerance is.

A: —assuming glue equals insulation is how fleets get grounded. Carbon is cathodic. 7075 pays the price if the barrier isn’t defined, qualified, and inspectable. A vague dashed line isn’t a material system, and you can’t sign off what you can’t verify.