Sourcing Aerospace Composite Parts and Panels
To buy composite parts well, specify the part category, the material and process specs, the NDI acceptance level and the coupon tests, because the fabricator creates the material properties during cure. Aerospace Sourcing matches your request to qualified composite fabricators, flows down those requirements, checks cure and material records and delivers one quote and one cert package.
What aerospace composites sourcing covers
It covers any part where the material is made at the same time as the part: laminates, bonded assemblies, sandwich panels and the tools used to cure them. Because the fabricator creates the material properties in its own oven or autoclave, buying composites is closer to buying a special process than buying a machined part.
Typical requests:
- Structural and secondary panels, including honeycomb sandwich panels for spacecraft and launch vehicle decks
- Brackets, clips, stiffeners and tubes in carbon or glass fiber
- Fairings, radomes, covers and closeouts
- Layup tools, bond fixtures, trim and drill jigs
- Repairs to damaged parts, either at the fabricator or in the field
- Coupons and test panels for allowables work or process qualification
Decide what the part is before you buy it
Classify the part as primary structure, secondary structure, non structural, tooling or prototype, and put that on the request. That one word sets which material controls, cure records, inspections and coupons a supplier must carry, and therefore most of the price.
| Category | What buyers usually require |
|---|---|
| Primary or flight structure | Qualified material on an approved list, program process specs, full cure records, ultrasonic inspection to an acceptance class, coupons per cure, AS9102 first article |
| Secondary structure, fairings and closeouts | Specified material and process spec, cure records, NDI to a defined method, reduced coupon testing |
| Non structural and GSE | Material and fiber callout, dimensional report, visual inspection, flammability or outgassing data where relevant |
| Tooling | Tool material, service temperature, vacuum integrity, dimensional verification at the stated condition |
On certified aircraft, FAA Advisory Circular 20-107B describes an acceptable, not the only, means of showing compliance for composite structure, and AC 21-26A covers quality control for manufacturing composite structures. Space programs usually work from their own specs, but many borrow the same discipline.
Material systems, storage and out-time
Specify the material by specification, not just by fiber type, and require proof that it was stored and handled within its limits. Two prepregs with the same fiber can behave very differently because the resin system governs cure temperature, service temperature and moisture behavior.
What to ask for:
- The material specification and, where your program has one, the approved product list or qualified material source
- Batch certs with manufacture date and the shelf life at frozen storage
- Freezer temperature records for the storage period
- Out-time logs per roll, and ideally per ply kit, showing the time out of the freezer is within the material data sheet limit at layup and at cure
- Thaw practice that keeps rolls sealed until they reach room temperature, so moisture does not condense on the material
Expired or over out-time material is a common first article finding, and it is difficult to recover from after cure. The engineering reasons, including how out-time leads to porosity, are explained on our composites fabrication reference page.
Choosing a cure route: autoclave, out of autoclave or oven
Autoclave cure gives the most consistent laminates and remains the norm for primary structure. Out of autoclave and oven cures cost less in equipment and suit large parts, provided the resin is formulated for it and the supplier controls bagging and out-time closely.
| Route | Why a buyer picks it | What it costs you in risk |
|---|---|---|
| Autoclave prepreg | Lowest porosity, best repeatability, most existing qualification data | Part size limited by the autoclave, higher hourly cost, fewer shops with large vessels |
| Out of autoclave prepreg (vacuum bag only) | Large parts, lower equipment cost, more potential suppliers | Very sensitive to out-time and bag leaks, needs resins designed for low pressure |
| Oven cure of wet layup or infusion | Tooling, prototypes, non structural parts and GSE | Lower and more variable fiber volume, less suited to flight structure |
Do not let a supplier switch routes on its own. Changing from autoclave to out of autoclave is a material and process change, and on qualified parts it needs engineering approval.
Design allowables and CMH-17
Your design values must come from data generated on the same material and process the supplier will use. That is why material and process substitutions are not a purchasing decision.
CMH-17, the Composite Materials Handbook, is the reference most programs use for how composite property data is generated and reduced into allowables. Volume 1 covers test planning, sampling, data reduction and statistics, Volume 2 holds statistically based property data for polymer matrix materials, and Volume 3 covers design, analysis and manufacturing guidance. When a supplier says a laminate is equivalent, ask whether the equivalence was shown with data under a plan your engineers accept. A supplier that cannot discuss this is unlikely to be the right source for structure.
Tooling is part of the quote
Expect tooling to be a line item on any new composite part, and decide early who owns it. The tool sets the shape and surface of the part and, on high temperature cures, much of its accuracy.
- Who owns it. If you pay for the tool, say that it is your property, how it is identified and stored, and that it moves with the work if you change suppliers.
- Tool material. Invar is common for high temperature carbon cures because its expansion is close to the laminate. Composite tools suit prototypes and moderate rates. Aluminum is cheaper but expands far more than carbon, which matters at cure temperature.
- Verification. Ask how the tool will be inspected before first use and how often after, and whether it is vacuum tested.
- Size. Large tools may be machined at a different shop than the one that lays up the part.
See our pages on controlled expansion alloys for Invar and large part machining for big tool bodies.
NDI: ultrasonic, tap testing and thermography
Require ultrasonic inspection for structural laminates, and name both the method and the acceptance criteria, usually by reference to your process spec. Without an acceptance class on the PO, the inspection proves very little.
| Method | What it finds | Standard reference |
|---|---|---|
| Ultrasonic, pulse echo or through transmission | Delaminations, porosity, inclusions in flat laminates and sandwich panels | ASTM E2580 covers ultrasonic testing of flat composite panels and sandwich core panels used in aerospace, to acceptance criteria set in the purchase order or contract |
| Flash thermography | Delaminations, disbonds, voids, inclusions and porosity, including in repair patches | ASTM E2582 covers infrared flash thermography of composite panels and repair patches used in aerospace |
| Tap testing | Disbonds and near surface voids in thin skins and sandwich structure | Usually set by the program process spec or repair manual; operator dependent, best as a screen |
Ask which zones need full coverage and which can be sampled, and require scan maps or images rather than a pass or fail stamp for primary structure. Our nondestructive testing reference compares methods in more depth.
Test coupons and which ASTM methods to call out
Coupons are how you verify the material you were not there to see cured. Specify whether they are needed per part, per lot or per cure load, how they are made, and the limits they must meet.
| Test | ASTM method | What it tells the buyer |
|---|---|---|
| Fiber, resin and void content | D3171 | Whether consolidation was good. Void content is the common acceptance number |
| Short beam strength | D2344 | A quick screen of cure and interlaminar quality |
| Tensile strength and modulus | D3039 | In plane tensile strength, modulus and Poisson's ratio of the laminate |
| Flexural strength and modulus | D7264 | Long beam flexural behavior in three or four point loading |
D7264 uses a long span, 32 to 1 span to thickness, while D2344 uses a short beam, so the two are not interchangeable. Traveler panels cured alongside the part are more representative than coupons cut from a separate panel cured another day. Ask for the test lab's identity and the raw data, not just a summary.
Honeycomb sandwich panels and potted inserts
For sandwich panels, specify the core, the facesheets, the adhesive and how every insert is installed and proven. Most sandwich panel problems are at the inserts and the edges, not in the middle of the panel.
- Core. Name material, cell size, density and ribbon direction. Aluminum and aramid paper cores behave differently in moisture, galvanic contact and machining.
- Bond. Film adhesive, surface preparation and cure all need records like a laminate cure.
- Inserts. Potted inserts are set in a drilled cavity filled with potting compound, usually epoxy. Load capacity depends on the potting quality and the strength of the core and skins, so pull out testing on representative samples is normal. ESA's insert design handbook, ECSS-E-HB-32-22A, is a common reference for insert design and testing on space panels.
- Edges and closeouts. Say how edges are sealed or closed out, and whether the core must be vented for launch depressurization.
Ask for insert locations to be verified after potting, since a shifted insert is a common reason a panel will not mount.
Outgassing for composites on space hardware
For anything inside a spacecraft or a vacuum test, require ASTM E595 data for the resin, adhesive, potting compound and any sealant or paint in the part. ASTM E595 measures total mass loss and collected volatile condensable material in vacuum at 125 C for 24 hours.
The levels historically used to screen spacecraft materials are 1.0 percent total mass loss and 0.10 percent collected volatile condensable material, and NASA keeps a public database of tested materials. Your contamination control plan may set tighter limits or require a vacuum bakeout of finished panels, which should be on the PO because it adds a step and a schedule hold. Passing E595 is a screen, not a guarantee of cleanliness. Our spacecraft and satellites reference covers contamination in context.
Repairs and the structural repair manual
Repair a composite part only to an approved repair: the structural repair manual (SRM) for the aircraft or vehicle, a program repair spec, or a specific engineering disposition. A repair outside those documents is a design change.
When sourcing a repair, send:
- The part number, serial number and the damage description, with photos and NDI results if you have them
- The SRM chapter or repair document that applies, or a statement that engineering disposition is needed
- Whether the part can travel to the repair shop or the work must be done on site
- Material and adhesive requirements for the repair, which may differ from the original laminate
- Inspection after repair, often ultrasonic or thermography of the patch
For civil aircraft, repairs are also governed by who may perform them, so tell us the aircraft's certification basis. Our aviation and MRO reference covers the repair side in more detail.
What drives composite cost and lead time
Material availability, tooling and the level of inspection usually set composite cost and schedule more than the layup. We do not publish prices or promise lead times, but these drivers show up in every quote:
- Material. Qualified prepregs are often made to order with minimum buys, and shelf life means suppliers rarely hold stock for a specific spec.
- Tooling. New tools must be designed, built and proven before the first part. Repeat orders on existing tools move faster.
- Cure route and size. Autoclave time is shared and scheduled. Very large parts limit the number of capable shops.
- Ply count and complexity. Ply drops, cores and inserts add hand labor and inspection points.
- Inspection and coupons. Full coverage ultrasonic and per cure coupon testing add days, especially at an outside lab.
- Trim, drill and assembly. Composite drilling needs dedicated tooling and edge sealing.
- Paperwork. Cure records, out-time logs and first article packages take real time to compile and check.
What to put on a composites RFQ
Send the drawing with the material and process specs, and state the part category. A complete request includes:
- Drawing and revision, ply table and any 3D model or flat patterns
- Part category: primary, secondary, non structural, tooling or prototype
- Material specification and approved product list, and whether substitutes are allowed
- Process specification for layup, cure and bonding, including cure route
- NDI method, acceptance class and coverage
- Coupon requirements, with ASTM methods and limits
- Core, adhesive and insert requirements for sandwich panels
- Outgassing limits and bakeout for space hardware
- Tooling ownership and whether tools exist
- Quantity, need date and export classification of the part and data
Our aerospace RFQ checklist covers the fields every request needs, and our AS9102 first article guide covers what the first part's report should contain.
How Aerospace Sourcing handles composites requests
We do not lay up parts ourselves. We match the request to composite fabricators whose materials, cure equipment and inspection fit the job, flow down your material, process and inspection requirements, and coordinate any outside steps such as tooling, NDI or coupon testing.
- One quote, one lead time, one point of contact and one purchase order across every shop involved
- Material certs, out-time logs, cure records and coupon results checked before shipment
- A certificate of conformance with every order, and other certs when the request requires them
Every supplier signs a flow down NDA before seeing your drawings, and controlled data moves only by secure transfer to US persons, as described on our confidentiality page and controlled programs page. Launch vehicle buyers will find more on our launch providers page, and spacecraft builders on our satellite manufacturers page.
Request a composites quote
Use the composites request form. It is preset for composites, so it asks for the material spec, cure route, NDI and coupon requirements, which are the details that decide which fabricators can quote. A person replies within one business day, and rush requests are prioritized.
Questions
Should I require autoclave cure on every flight part?
Not automatically. Autoclave cure gives the most consistent laminates and has the most qualification data, so it remains the default for primary structure. Out of autoclave prepregs can produce good parts and suit large components, but only with resins designed for low pressure and tight control of out-time and bagging. What matters is that the cure route matches the data behind your allowables, and that the supplier cannot change it without approval.
What records prove a composite part was made correctly?
Material certs with batch and manufacture date, freezer storage records, out-time logs, the cure record with part or tool thermocouple traces plus vacuum and pressure, NDI results with scan maps for structure, coupon test reports, a dimensional report and, for a new part, an AS9102 first article. Every order we deliver includes a certificate of conformance, and the other records are flowed down when your request requires them.
Which coupon tests should I ask for?
Constituent content by ASTM D3171 and short beam strength by ASTM D2344 are common process control checks, because they show whether the laminate consolidated and cured properly. Tensile testing by ASTM D3039 and flexural testing by ASTM D7264 are used when you need in plane or flexural properties verified. Your process spec should set which tests, how often and the acceptance limits.
Is tap testing enough for a sandwich panel?
It is useful as a screen for disbonds and near surface voids, especially in thin skins, but it depends on the operator and does not give a permanent record. For flight structure, most programs also require ultrasonic inspection or thermography to a defined acceptance level. Use tap testing where your spec or repair manual allows it, and ask for maps of what was found.
Do composite parts for satellites need outgassing data?
Yes, for every organic material in the part: resin, adhesive, potting compound, sealant and coating. ASTM E595 is the usual test, and the levels historically used to screen spacecraft materials are 1.0 percent total mass loss and 0.10 percent collected volatile condensable material. Your contamination control plan may be stricter or require a vacuum bakeout of the finished part, so include it on the purchase order.
Who pays for and owns composite tooling?
That is a commercial decision, so settle it in the quote. If you pay for the tool, the purchase order should state that it is your property, how it is marked, how it is stored and maintained, and that it can be moved if you change suppliers. Tooling is often the longest item on a first order, so knowing whether tools already exist changes the lead time a lot.
Related
Sources
- Wichita State NIAR: about CMH-17
- FAA: AC 20-107B Composite Aircraft Structure
- FAA: AC 21-26A Quality Control for the Manufacture of Composite Structures
- ASTM D3039 tensile properties of polymer matrix composites
- ASTM D7264 flexural properties of polymer matrix composites
- ASTM D3171-22 constituent content of composite materials
- Instron: ASTM D2344 short beam strength testing
- ASTM E2580 ultrasonic testing of flat panel composites and sandwich core
- ASTM E2582 infrared flash thermography of composite panels and repair patches
- NASA GSFC: outgassing database user guide (ASTM E595 screening levels)
- Politecnico di Milano thesis: insert allowables using ECSS-E-HB-32-22A
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