Composite Layup Room Readiness Checklist

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13 critical items still open - these are the highest-risk gaps.

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Environment and housekeeping

Temperature and humidity in the layup room are within the process specification limits and recordedCRITICALPositive pressure or filtered air confirmed where the specification requires a controlled areaCRITICALRoom particulate or contamination checks completed per scheduleNo silicone, mold release aerosols or unapproved lubricants in the areaCRITICALFloors, tables and cutting surfaces clean and free of fiber debrisPersonal protective equipment, gloves and garments available and in good condition

Material and kitting

Prepreg lot, certificate of conformance and shelf-life status verified before useCRITICALOut-time tracked and remaining out-life covers layup, bagging and cureCRITICALMaterial allowed to reach room temperature in the sealed bag before opening to prevent condensationCRITICALPly kit matches the ply book: orientation, count and material codeCut plies labeled and stored on the backing paper in the correct sequenceCore, inserts and adhesive films within shelf life and correctly identified

Tooling and release

Tool identified, calibrated or inspected as required and in current revisionCRITICALTool surface free of residue, scratches, dents and previous resin build-upTool vacuum integrity tested or leak checked per scheduleCRITICALRelease agent or film applied per specification and allowed to cureLocating features, dams and caul plates present and secureTool thermocouple ports and vacuum ports are clear and labeled

Layup, debulk and bagging

Ply orientation checked against the laser projector or template for each plyCRITICALBacking paper and any foreign material removed from each ply before the next is placedCRITICALDebulk performed at the frequency and vacuum level the traveler requiresBagging materials are the correct type and temperature rating for the cureBag has sufficient pleats and no bridging at radii or cornersVacuum ports and lines connected, and bag leak-down test is within the allowed rateCRITICALThermocouples attached to coldest and hottest expected locations

Records and handover

Traveler complete, signed and includes material lot, tool and operator traceabilityCRITICALOut-time record updated and unused prepreg returned to cold storage correctly labeledScrap and offcuts segregated and logged by lotDeviations written up and routed to quality before the part goes to cureCRITICALCure cycle record opened and linked to part serial number

Items marked critical should be satisfied before layup begins. Any failed critical item stops work until it is resolved or dispositioned by quality or engineering. Adapt the list to your controlled process specification.

Enforce layup holds in the MES

Optional: discuss how critical checks can become hold points on the work order.

Optional. The tool and every export work without this. No spam.

How to use the checklist

Use it at the start of a shift for the room and at the start of each job for the material, tool and bag. Work through each group in order and tick items as they are confirmed. Items marked critical block the job if they fail. Print the page or export it to PDF to file with the traveler. Many shops split the groups between the technician, the lead and quality; the grouping here makes that easy. Adjust wording and limits to match the controlled process specification that governs your parts.

Treat the critical items as hold points, not reminders.
Record the actual temperature, humidity and leak rate, not just a tick.
Review failures weekly to find recurring causes such as tool wear or consumables.

Why these checks matter

Contamination is a common root cause of bond failures and porosity, which is why silicone and uncontrolled release agents are banned from many composite areas. Temperature and humidity affect tack and moisture pick-up. Out-time and shelf-life limits protect resin flow and cure behavior. A leaking bag lets air into the laminate and creates voids that ultrasonic inspection will later reject. Ply orientation errors are among the costliest, because a part with the wrong angle can pass visual inspection but fail structurally.

Standards and references

Aerospace composite work typically follows customer process specifications and industry practices for prepreg handling, such as those found in the SAE and CMH-17 guidance, plus the quality management requirements of AS9100. The thresholds for room conditions, leak rates and debulk frequency vary by material and program, so this list refers to your specification rather than quoting numbers. Where a customer requires a particular form, use that one and treat this as a supplementary shop-floor aid.

Common mistakes

Teams often tick the room environment from memory instead of reading the instrument. Another common mistake is opening a cold prepreg bag early, which pulls moisture onto the tacky surface and shows up as porosity later. Vacuum checks are sometimes done on the bag but not on the lines and fittings, so a leak in a quick-disconnect goes unseen until the cure. Finally, skipping the debulk or doing it at the wrong vacuum level because of schedule pressure is a known driver of thickness and void problems on thick laminates.

Frequently Asked Questions

What temperature and humidity should a layup room maintain?

It depends on the material and specification. Many aerospace prepreg rooms hold roughly 18 to 24 C and 30% to 65% relative humidity, but you must use the limits in your controlled process specification and record actual readings.

Why must prepreg thaw before the bag is opened?

If the bag is opened while cold, moisture from the room air condenses on the material. That water becomes voids or porosity during cure. Let the sealed bag reach room temperature, often a number of hours depending on roll size, before opening.

How often should the layup tool be leak checked?

Frequency is set by the process specification and tool condition, often at tool acceptance and at defined intervals or after repairs. The bag is leak checked every cure. A tool with a failed leak test should not be used until repaired and retested.

Who should sign the checklist?

Typically the layup technician completes it and the lead or quality inspector verifies the critical items. Follow your quality system's rules for who may sign, and keep the form with the part traveler for traceability.

If you want pre-layup checks and holds enforced in the MES with the results stored against the work order, Netray can scope that integration with your ERP and quality system.

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