Composite NDT: Choosing UT, Thermography or Shearography

Choose an examination around the composite structure and the decision

Choosing NDT for a composite component starts with its construction and the question that must be answered. A solid laminate, an adhesive joint and a sandwich panel can present different inspection problems, even when all three are called carbon fiber parts. Ask whether the purpose is to investigate a reported event, examine a manufacturing concern, support a repair assessment or establish an agreed baseline. That purpose determines which evidence is useful.

This guide is for U.S. quality teams, inspection buyers and technical coordinators preparing that discussion. It compares ultrasonic testing, active thermography and shearography at the level of method selection and evidence planning. The sample brief is hypothetical. Examination settings, applied loads, acceptance limits and repair decisions belong to the responsible technical authorities and the applicable instructions, rather than a general purchasing article.

Identify the construction before comparing equipment

Start with the controlled part identification, drawing revision and available construction information. Record whether the relevant region is a laminate, a bonded assembly or a sandwich structure, and identify the interfaces that matter. Include accessible surfaces, curvature, transitions, coatings and known repair history where relevant. If information is unavailable, record the gap and ask the technical owner how it affects the proposed examination.

Avoid substituting a material trade name for a construction description. An inspector may need more than a statement that the part is composite to assess a proposed technique. Conversely, do not send confidential design information to every prospective bidder without authorization. Prepare a suitable initial brief, identify the information needed for technical review and use the owner's approved sharing process for the detailed package.

Define the condition at inspection. A manufacturing examination before assembly may have access that an in-service examination cannot reproduce. A repair configuration may differ from the original region. Make those differences explicit when a supplier refers to previous experience or an earlier demonstration. Experience on a similar material is useful background, but the buyer still needs a clear explanation of the relevance to this particular construction and task.

Write separate questions for detection, characterization and disposition

Detection asks whether a relevant response can be identified under the examination conditions. Characterization asks what can be established about that response. Engineering disposition asks what the finding means for the component and what action is authorized. These questions are connected, but they should not collapse into a request for a single green or red result without a defined basis.

For example, locating an area that differs from its surroundings is not automatically equivalent to measuring a disbond's physical boundary. An image may support a follow-up examination without supporting a final repair decision. Require the proposed report to distinguish observations, interpretations, limitations and conclusions. The responsible reviewer should be able to see which evidence supports each conclusion and which uncertainty remains unresolved.

Ask who owns the decision when the result is ambiguous or outside the agreed scope. A technician should have a route to escalate an unexpected condition rather than improvise a new acceptance rule. The buyer should also know whether further examination requires a variation to the purchase order. Agreeing those arrangements before mobilization reduces the pressure to turn an incomplete result into a definitive answer simply to close a job.

Ultrasonic testing: ask what the acoustic examination demonstrates

Ultrasonic techniques use acoustic responses to investigate the component. For a composite application, the technical proposal should explain the intended examination arrangement, relevant interfaces, coverage and output. The buyer's role is to obtain evidence that the arrangement addresses the required task, rather than selecting a probe solely from a catalog or assuming that a technique used on a metal weld transfers directly to a laminate.

Oak Ridge National Laboratory's publication on ultrasonic inspection of composite materials provides a research reference on phased-array inspection in this field. Its application to a procurement discussion is a request for the supplier's own supporting evidence for the proposed component. A research result or a phased-array label does not establish universal superiority for every composite geometry, discontinuity or access condition.

Ask what the recorded data allows a reviewer to revisit. A coverage image, a selected signal and a complete retained examination dataset can support different levels of review. Specify the necessary location references and any regions not evaluated as planned. If comparison with a previous survey is required, agree how the two examinations will be related and how differences in configuration or coverage will be communicated.

Thermography: distinguish the thermal response from the underlying condition

Active thermography examines a thermal response following an appropriate excitation. The useful result depends on the construction and the question being investigated. NASA's study of composite sandwich structures, published in 2014, discusses flash thermography for face-sheet impact damage and face-sheet-to-core disbond, along with limitations in investigating the core. The study also used CT to investigate and corroborate findings. It is a specific research example, not a current approval for every sandwich panel.

For a service proposal, ask the technical owner to define the permitted excitation and the conditions under which the examination is to be performed. The supplier should identify the resulting records, relevant restrictions and evidence supporting the proposed interpretation. Do not translate a general description of rapid coverage into a guaranteed project duration or assume that every thermal contrast has the same physical cause.

Include environmental and surface conditions in the feasibility discussion when they matter to the proposed method. Ask how the examiner will document conditions that prevent a useful result and what happens if part of the planned area cannot be evaluated. Those questions are more valuable to a buyer than asking for an unsupported universal depth or minimum defect size. The appropriate capability statement must be tied to the actual application.

Shearography: review the loading arrangement as part of the examination

NASA White Sands' shearography overview describes comparing observations of a surface before and under an applied load or stress to identify differences associated with underlying conditions. The overview lists several kinds of excitation. It does not provide a universal loading instruction for an aircraft panel, pressure vessel or other customer's component.

A useful quotation should therefore identify who approves the examination arrangement and how the permitted loading conditions will be established. The buyer must not treat the excitation as a harmless accessory to the camera. Its suitability is part of the technical review. Ask what evidence supports the interpretation for the relevant construction and how normal structural features will be distinguished from conditions requiring investigation.

Clarify whether the proposed output is a screening result, a characterization result or part of a broader examination sequence. Request records sufficient to relate the observed response to the component and the agreed examination conditions. If the team expects a final dimensional boundary or a serviceability conclusion, have the supplier state explicitly whether the proposed work can support that requirement and what additional evidence would be needed.

Compare the three methods without creating a universal ranking

A useful comparison keeps the decision criteria consistent. Ask each supplier to address the same construction, suspected condition, access arrangement, required regions and reporting question. Compare what each proposal can demonstrate and what remains outside its supported scope. The best fit may involve complementary examinations, but a second method should have a defined purpose rather than being added merely to make the package appear more comprehensive.

The following table is an editorial discussion aid. It summarizes questions to ask, not an approved technique-selection chart or a statement of guaranteed detection capability. The responsible technical authority must decide which methods and procedures are appropriate for the actual component.

Do not compare the best advertised capability of one configuration with the fastest advertised coverage of another. Ask for a complete proposed workflow for your part. Include preparation, access, acquisition, interpretation, review and reporting in the comparison. A method that is convenient to deploy may still be unsuitable for the required conclusion, while a technically useful method may need additional arrangements that belong in the schedule and cost.

Use representative evidence before a difficult production assignment

When the application requires a demonstration, agree the specimen or component population with the responsible authority. Record how the items represent the construction, geometry, relevant conditions and access constraints. Distinguish naturally occurring findings from manufactured features and document how any reference condition was established. A well-labeled demonstration is more useful than a collection of attractive images with uncertain provenance.

Include the questions the demonstration must resolve. The team may need evidence about coverage at a transition, the interpretation of a particular interface or the usability of the final reporting package. Give each question an owner and an agreed way to record the outcome. If the demonstration leaves a question unresolved, carry it into the next review rather than treating attendance at the demonstration as proof that the capability was accepted.

Keep the demonstration configuration linked to the proposed work. Changes in component construction, technique, equipment, software or access should be reviewed for their effect on the evidence. The review need not assume every change invalidates everything; it should establish which conclusions remain supported and which need further work. That is a more usable approach than either ignoring changes or demanding a completely new qualification without considering their significance.

Give disagreements between methods a review route

If two examinations produce different observations, first confirm that they concern the same physical region and condition. Check the location references, examination dates, component configuration and recorded limitations. Different methods observe different responses, so a disagreement should become a technical review question rather than an automatic reason to discard whichever result is inconvenient. The reviewer needs the original evidence from both examinations to assess the issue.

Agree how the final record will describe an unresolved difference. It may require additional information, a different authorized examination or an engineering decision about the available evidence. Record the actual disposition and its authority. Avoid combining two uncertain findings into an apparently certain conclusion through an informal majority vote. The commercial scope should allow the inspection provider to report an unresolved issue honestly, with a clear route for obtaining the next instruction.

A hypothetical brief for an impacted sandwich panel

Imagine a maintenance coordinator receiving a report that a removable composite sandwich panel was struck during handling. The coordinator has the component identifier and a photograph but does not yet have an authorized inspection instruction for the event. The immediate purchasing task is to obtain the appropriate technical direction and a scoped examination proposal, not to select a method from the appearance of the photograph alone.

The coordinator gathers the event description, affected location, available construction information, previous repair records and access conditions. The responsible engineering or maintenance authority identifies the applicable instructions and decision route. Prospective inspection providers are then asked to explain how they would perform the authorized scope, what records they will deliver and how they will report any area that cannot be evaluated as required.

Suppose an initial examination identifies an area needing further investigation. The report should connect the observation to its location and examination conditions, without presenting an unsupported repair boundary. The responsible authority determines the next action under the applicable process. This fictional sequence demonstrates how to preserve responsibilities and evidence; it does not establish that any particular combination of methods is sufficient for a real damaged panel.

Keep aircraft requirements and general industrial guidance distinct

The FAA's AC 20-107B record describes guidance concerning composite aircraft structure and identifies design, manufacturing and maintenance considerations. The FAA states that the advisory circular provides an acceptable means of showing compliance within its scope and is not itself mandatory or regulatory. Reading the circular does not create an inspection or repair authorization for a specific aircraft.

For aviation work, identify the actual maintenance instructions, engineering direction and approval responsibilities applicable to the component and operator. For other industries, identify the corresponding owner and contractual requirements. Do not copy an aircraft example into a wind-energy or marine work order and assume that its acceptance basis transfers. A relevant example can help frame questions without becoming the governing instruction.

Make the report usable by the person who must act on it

Agree the reporting structure before fieldwork. Include the component and revision identity, examined regions, relevant configuration records, observations, limitations and the basis for the conclusions the examiner is authorized to make. Link photographs and data to identifiable locations. If multiple methods are used, preserve their separate findings and explain how they relate instead of merging them into one image that hides the source of each observation.

Ask a receiving reviewer to use a sample package to locate a reported area and understand what was examined. Confirm how any later revision will be issued and how the superseded report will be identified. Our inspection report buyer review guide and report amendment guide provide practical handover questions. A clear record can reduce avoidable clarification without claiming to improve the underlying detection capability.

Prepare an RFQ that invites a useful technical answer

Include the component location, available access, controlled references, intended decision, work window and required deliverables in the request for quotation. Identify which technical issues must be resolved before an examination can be scheduled. Ask bidders to separate their assumptions and exclusions from the committed scope. If the part must travel to a laboratory, assign packaging, transport, condition checks and return responsibilities explicitly.

Compare actual quoted costs using the free inspection quote planner after the technical scopes have been aligned. Keep unknown items visible instead of entering a convenient zero. A commercial comparison should help the buyer understand the offer, while the technical authority determines whether it addresses the examination need. The planner does not supply composite inspection rates or approve a method.

When the brief is ready, browse inspection providers or submit a scoped inspection request. Ask for evidence of the relevant personnel qualifications and application experience, and confirm current availability directly. A directory profile is a starting point for that assessment. The most useful supplier response is one that explains the supported task, the evidence it will produce and the limits that the decision-maker must understand.

Sources and editorial scope

Primary sources checked October 31, 2026: ORNL ultrasonic composite inspection publication, NASA sandwich-structure NDE study, NASA White Sands shearography overview, and FAA AC 20-107B record. These established sources are not presented as new product launches. The comparison questions and fictional panel example are original editorial planning aids.