Storage life, HexPly 8552
Where to buy| Item | Value |
|---|---|
| Tack life | 10 days at 73 °F (23 °C) |
| Out life | 30 days at 73 °F (23 °C) |
| Shelf life | 12 months at 0 °F (-18 °C), maximum, from manufacture |
| Resin content, tapes / fabrics | 33–38% / 32–42% |
Hexcel sheet (2020). Out life is the accumulated time at room temperature between removal from the freezer and cure.
Autoclave cure procedure, HexPly 8552
| Step | Instruction |
|---|---|
| 1 | Full vacuum and 15 psig |
| 2 | Heat at 3–5 °F/min to 225 °F |
| 3 | Hold at 225 °F for 30–60 min |
| 4 | Raise pressure to 85–100 psig; vent vacuum at 30 psig |
| 5 | Heat to 350 °F and hold 120 ± 10 min |
| 6 | Cool at 2–5 °F/min to 150 °F and vent |
Hexcel lists alternative cure cycles on request. A repair uses the cycle in the SRM or material specification, usually with a heat blanket and bag rather than an autoclave.
What the FAA handbook says
Prepreg is available as unidirectional tape, woven fabric, continuous rovings and chopped mat; many aerospace prepregs are epoxy and cured at 250 °F or 350 °F, in an autoclave, oven or by heat blanket (p. 7-8). It is stored and bought on a roll in a sealed bag against moisture.
Prepreg is temperature sensitive: too high starts the cure, too cold makes it hard to handle (p. 7-27). Prepregs with 32–35% resin are typically no-bleed systems: bleeding them leaves a resin-starved repair (p. 7-28).
Handling prepreg
| Step | Action | What to do |
|---|---|---|
| 1 | Thaw | Bring the sealed bag to room temperature before opening so moisture does not condense. |
| 2 | Log | Record out time against the out life. |
| 3 | Protect | Cover unprotected sides with parting film; keep clear of dust, oil and vapours. |
| 4 | Cure | Use the SRM cycle; do not bleed a no-bleed system. |
Limits — when NOT to use this
- One system’s numbers.
- Log the clock. Out time is accumulated, not reset by a return to the freezer.
Where to buy
Distributors coming soon.
Sources
- Hexcel HexPly 8552 Product Data Sheet (US units, 2020) — neat resin properties, prepreg physical properties, cure procedure, storage life.
- FAA-H-8083-31B, AMT Handbook — Airframe, Volume 1 (2023), Chapter 7 — prepreg (pp. 7-8, 7-25, 7-27, 7-28).