HiCAM_GPE-RFI on Auto Insp System__Final 03-31-2025.pdf

CUI

Request For Information (RFI)

For

NASA Langley Research Center (LaRC)

Automated Inspection Systems

March 31, 2025

1.0 Introduction

NASA/Langley Research Center (LaRC) is hereby soliciting information from potential commercial sources for an automated inspection system (AIS) capable of ply-by-ply inspection of carbon fiber reinforced polymer (CFRP) during the automated fiber placement (AFP) aerospace composite manufacturing process.

The National Aeronautics and Space Administration (NASA) LaRC is seeking capability statements from all interested parties, including all socioeconomic categories of Small Businesses and Historically Black Colleges and Universities (HBCU)/Minority Institutions (MI) for the purposes of determining the appropriate level of competition and/or small business subcontracting goals for the Hi-rate Composites for Aircraft Manufacturing (HiCAM) Project. The Government reserves the right to consider a Small, 8(a), Women-owned (WOSB), Service-Disabled Veteran (SD-VOSB), Economically Disadvantaged Women-owned Small Business (EDWOSB) or HUBZone business set-aside based on responses received.

Under the Hi-rate Composites for Aircraft Manufacturing (HiCAM) Project, the National Aeronautics and Space Administration (NASA) /Langley Research Center (LaRC) is hereby soliciting information from potential commercial sources for an automated inspection system (AIS) capable of ply-by-ply inspection of carbon fiber reinforced polymer (CFRP) during the automated fiber placement (AFP) aerospace composite manufacturing process. AFP has traditionally been used for building large acreage structures like wing skins, spars, and fuselages. Through the years, the AFP equipment has improved significantly in terms of meeting high material placement rates, but inspection processes have lagged behind. Some of it is due to the lack of advanced technology in this area while some of it is due to AFP users having different inspection requirements that equipment suppliers have to meet. As a result, significant time is spent on manual/visual inspection of very large parts that significantly slows down the overall rate of the composites aircraft primary structure manufacturing process. In addition, the lack of recorded data limits understanding and improving for the process. The primary goal of the HiCAM project is to demonstrate manufacturing approaches and associated technologies for large composite airframe structures that enable high-rate production (up to 80 aircraft per month) with reduced cost and no weight penalty versus 2020 technologies. The Project will develop and mature affordable high-rate composite manufacturing and assembly technologies, with reduced equipment and tooling costs, enabling a faster, more cost-effective production cycle for lightweight airframe structures. In this regard, NASA has partnered with the United States Aircraft manufacturing industry to define and standardize the inspection requirements for AFP with the goal of identifying a commercially available, or commercially developed, AIS system capable of meeting the standardized inspection requirements. These standardized inspection requirements are defined in the proceeding sections.

AFP Features During the process of standardizing, certain AFP features must be measured. A list of these features is provided in Table 1 and described further in a technical publication [1]. The size and occurrence of AFP defects can vary depending on part geometry, tow width and processing parameters such as placement speed, temperature and compaction load. The AFP features which commonly occur are listed in Table 1 and the AFP subject matter experts from three US aerospace composites manufacturers documented the following assumptions during the development of Table 1:

• Define "Feature" and "Defect": Everything is listed as a "Feature". If it exceeds a processing specification allowance, it becomes a "Defect".

• Define "Tow": Individual strips of prepreg are referred to as "tows" in this document.

• Define T2T and C2C: "Tow-to-tow" (T2T) refers to neighboring tows within one laid up course, "course-to-course" (C2C) refers to neighboring tows between two laid up courses.

• Scope - Material: thermoset, carbon-fiber prepreg

• Scope - AFP: This process of standardization captures layup features relevant to AFP machines laying tow widths from 1/8" up to 1/2"

• Scope - No Aggregated Features: Aggregated features (cumulative gap, splice density, etc.) are out-of-scope. Once individual features can be located and measured, any aggregation is possible through software.

• Scope: Features listed in Table 1 are all features which have been identified as potentially occurring during the AFP process. Column # 2 identifies whether these features are “Key” (by yes/no). All “Key” features are considered critical to be identified, located, and measured by the AIS, because these types of features are common and can lead to performance knockdowns. Other features listed in Column #1 which are indicated as not “Key” in column #2 are features which are not common to all AFP parts but are known to occur. Identification, location, and measurement of these types of features is highly desirable, but not critical. Columns # 5 through #8, rows #2 through #32 are left blank for the responder to populate with the capabilities of their automated inspection system. Examples of potential responses are provided below following Table 1. Note: the respondent should provide a response which explains the capabilities of their respective AIS equipment and algorithms to identify, locate and measure all of the features listed in Table 1 regardless of whether the feature is listed as “Key” or not, as the response will indicate how advanced and/or robust are the capabilities of the subject AIS. Any further communication from NASA and its industry partners after receiving responses listing these capabilities will depend on a ranking of responses and the communicated capabilities of an AIS to detect any and all features listed in Table 1.

Table 1. AFP Features of Interest

It is recommended that any and all responses to this RFI include a copy of Table 1 with columns 5 through 8, and rows 2 through 32 populated by the responder according to the capabilities of their automated inspection system.

Row/ Column # 1 2 3 4 5 6 7 8

1 Feature Key AFP Feature?

Feature Type Feature Dimension to be Measured?

Size Detectable

100% of the time Size Detectable ≥ 90% of time

Size Detectable ≥ 70% of time

Measurement Fidelity

2 Individual Tow Gap Yes Continuous Width (in) 3 Individual Course Gap Yes Continuous Width (in) 4 Individual Tow Overlap Yes Continuous Width (in) 5 Individual Course Overlap Yes Continuous Width (in)

Tow End Location Yes Continuous

-Distance from nominal (in)

Ply Edge Location Yes Continuous

-Distance from nominal (in)

Ply/Course Orientation No Continuous

-Angular offset from nominal in degrees

9 Tow Splice Yes Attribute Presence / Absence

Wrinkles No

Attribute (Continuous)

Presence / Absence:

Length, Depth (Height) (in)

Puckers No Continuous

Presence/Absence:

-Height and length (in)

Twisted Tow Yes

Attribute (Continuous)

Presence/Absence:

-length (in)

Edge Folds No

Attribute (Continuous)

Presence/Absence -Length -% of tow folded over

V Folds (Tow Ends) No

Attribute (Continuous)

Presence/Absence -Length (in) -% of tow folded over

Untacked Tow No

Attribute (Continuous)

Presence/Absence -Length (in) -Untack height(in)

Missing Tow Yes

Attribute (Continuous)

-Presence/Absence Length (in)

Bridging No

Attribute (Continuous)

Presence/Absence -Length (in) -Height (in)

Damaged Tow No

Attribute (Continuous)

-Length of damage (in) -Width of damage (in)

Extra Tow Yes

Attribute (Continuous) -Presence/Absence

Blown Tow No Attribute -Presence/Absence

Whiskers No

Attribute (Continuous)

-Presence/Absence -Length

Stringer No Attribute (Continuous)

-Presence/Absence -Gap widths should still be accurately measured (see Tow Gap and Course Gap, above)

Fuzzball - Surface Yes

Attribute (Continuous)

-Presence/Absence -Size (major diameter) (in)

Fuzzball - Buried Yes

Attribute (Continuous)

-Presence/Absence -Size (major diameter) (in)

Resin Ball - Surface No

Attribute (Continuous)

-Presence/Absence -Size (in)

Resin Ball - Buried No

Attribute (Continuous)

-Presence/Absence -Size (in)

FOD - Films - Surface Yes

Attribute (Continuous)

Presence/Absence -Area (in2) -Shape

FOD - Films - Buried No Attribute (Continuous)

Presence/Absence -Area(in2) -Shape -Ply depth

FOD - Particulate - Surface No

Attribute (Continuous)

Presence/Absence -Particle sizes (in) -Particle count

FOD - Particulate - Buried No Attribute (Continuous)

Presence/Absence -Particle sizes (in) -Particle count -Ply depth (in)

FOD - Liquid - Surface No

Attribute (Continuous)

Presence/Absence -Affected area(in2) -Amount of liquid

FOD - Liquid - Buried No Attribute (Continuous)

Presence/Absence -Affected area(in2) -Amount of liquid -Ply depth (in)

The respondent should provide values for each of these cells in the table based on the experience of detecting and measuring these types of features with their particular AIS device.

In addition to populating as many of the empty cells in Table 1 as possible, the responder should also provide information on the type of testing, or trials, conducted to determine these capabilities. Note that given the state of the art, it is anticipated that most systems will not detect all features in the list. Information shall be provided for cases where features were detected using only flat tooling during AFP, where the features were programmed to occur prior to measuring with the AIS system or were the features allowed to occur naturally on contour, and/or complex contour tooling and parts. Please indicate the material and AFP parameters used during placement and occurrence of these features as well as the speed of the AIS device when detecting the features for which the table values are populated.

Measurement Criteria and examples of AFP Features In addition to populating Table 1 and explaining the procedures utilized to arrive at the values placed in the table, respondents should also be mindful of the following assessment criteria for the various feature types:

• Location of features:

o When detected, features must be located to within at least the following positional accuracy:

o The sequence (ply) in which the feature was found must be correctly reported.

o The particular tow containing the feature, or interface between two tows, must be correctly reported.

o The distance along the tow (or interface), as measured from the tow's add or cut end, must be accurate to within +/- 0.5 in, except for Tow End Location which is a special case (see Assessment criteria for Attribute (Continuous) type features, below).

o It is desirable to provide feature location in (X, Y, Z) coordinates o It is desirable that the measurement system can indicate, for any measured feature, whether it is inside or outside of the engineering edge of part (EEOP or "trim line").

• Assessment criteria for Attribute type features: Minimum desired probability of detection (POD) o An “Attribute” type feature is a feature the detection of which is all that’s measured. (Of course, the location of any detected feature must be reported, as described above.)

o POD 90/95: 90% of the most-difficult-to-detect rejectable features ("defects") are detected with 95% confidence (though see the special case of the “Tow End Location” feature below, in the Assessment criteria for Attribute (Continuous) type features)

• Assessment criteria for Continuous type features:

o A “Continuous” type feature is a feature for which a continuous variable about it must be measured (for example the width of a gap measurement). (Of course, the location of any detected feature must be reported, as described above.)

o The standard measurement system analysis (MSA) metrics will be measured, to be recorded under the heading “Measurement Fidelity” in Table 1:

o Bias: How accurate is the measurement system? The average of differences between measured values and the true values o Linearity: A measure of the consistency of Bias over the range of the measured parameter. At least measure multiple features which span 130% of the likely range of sizes.

o Variance: How repeatable is the measurement system? Gage R&R standard deviation. The standard deviation of repeated measurements of the same feature with one sensor, and possibly also repeated measurements of the same feature with multiple sensors.

o Measurement Density: The spacing of successive measurements of a Feature type, in inches, shall be recorded. It is desirable that measurements be made at least every inch, or perhaps 1.5 inches, along the layup direction.

o Measurement Distribution: For continuous Feature types measured over large areas (e.g. gaps and overlaps), the measurement locations should show a fairly uniform distribution (i.e. avoid islands of missing measurements, and high-density clumps of measurements) o Layup or Inspection Speed: The speed at which layup (or inspection if separate from layup) occurred, in inches-per-minute, shall be reported in the discussion section of the response- following the Table values.

• Assessment criteria for Attribute (Continuous) type features:

o An “Attribute (Continuous)” type feature is a feature for which the authors’ prime concern is its detection, but for which measurement of a continuous variable about it (for example its length) would also be useful. (Of course, the location of any detected feature must be reported, as described above.)

o Both detection and measurement of these features is valuable, but due to their natures, and the natures of different types of inspection systems, it is understood that sometimes these features may be detectable but not measurable. In general, measurement of these features should conform to the Assessment criteria for Continuous type features immediately above.

However, adjustments should be made where it makes sense. For example, a measurement density of 1.0 in may be too coarse to be useful for sizing fuzzballs.

o For Attribute (i.e., “detection”) purposes, the “Tow End Location” Feature is a special case. Since all tow ends (adds and cuts) for a sequence can be anticipated from that sequence’s programming, tow ends (or at least the locations where tow ends should be) must be detected 99% of the time.

An example of how to populate Table 1 as a part of the response to this request for information on automated inspection of AFP features is provided for the “Key” feature listed in Table 1 in column #1, row #2: “Individual Tow Gap”. Tow Gap features commonly occur during AFP of complex-contour parts in convergence zones. Again, a tow gap feature is only considered a defect when the size, and/or location exceeds the manufacturer’s specification allowance. Both a computer aided design (CAD) image as well as a digital photo of an actual tow gap are shown in Figure 1, taken from the cited publication [1].

Figure 1. CAD image (left) and photo (right) of an overlap/gap feature (from [1]).

The digital photo example was obtained from the first ply down on top of the tool to aid in visibility. Gap and Overlap features of a placed tow should be identifiable by the inspection system regardless of the ply location in the laminate stack. As indicated in Table 1, an “Individual Tow Gap” is a key feature and a continuous type feature. In addition to the AIS being capable of identifying the occurrence and location of an “Individual Tow Gap” the principal attribute of such a feature is its width, as indicated in column #4, row #2. Column#5 of this row requests the response of the width of the feature which the AIS can detect 99% of the time. Columns #6 and #7 request the width of the tow gap which the AIS can detect ≥90% and ≥70% of the time, respectively. These values are requested in order to gauge the probability of detection (POD) of this feature type. It is expected that the tow gap width the inspection system can detect 99% of the time will be slightly larger than the widths that the system can detect ≥90% and ≥70% of the time. In addition to the capability of detecting the occurrence of tow gaps, it is also critical to understand the AIS’s capability to measure and report the actual width of the tow gap feature. This capability aids in the decision-making as to whether the tow gap feature exceeds the specification and must thereby be treated as a defect that must be corrected. Therefore, Column #8 requests the respondent to indicate how accurately and repeatably the width can be measured. For Example:

Row/ Column # 1 2 3 4 5 6 7 8

1 Feature Key AFP Feature?

Feature Type Feature Dimension to be Measured?

Size Detectable

100% of the time Size Detectable ≥ 90% of time

Size Detectable ≥ 70% of time

Measurement Fidelity

2 Individual Tow Gap Yes Continuous Width (in) 0.016 0.013 0.010

Layup Inspection Speed: 1200ipm Bias:+0.002" Linearity: - 0.003"@0.012" gap, +0.003 @ 0.030" , +0.006" @ 0.060" Variance:Gage R&R 1σ = 0.005" Measurement Density: 1 measurement per inch Measurement Distribution: [Plot showing spatial distribution of measured points]

Figure 2. Example of populated Features Table for continuous-type feature “Individual Tow Gap”

The example values presented in Figure 2 are by no means meant as target values but simply to serve as example of the format of data desired that be provided as information describing the capabilities of the AIS from each individual company respondent.

Table 1 Row #12 is an “Attribute (Continuous)” type feature: a twisted tow. Figure 3 shows examples of a twisted tow

Figure 3. Twisted Tow Feature: CAD image (left) and by digital photograph (right).

For “Attribute (Continuous)” type features, the primary concern is that they be detected.

Measurement of the feature size is also valuable, but may or may not be achievable. Figure 4 shows an example of how Table 1 might be filled out to capture inspection system capabilities for twisted tows.

Figure 4. Example of populated Features Table for Attribute (Continuous)-type feature

“Twisted Tow”

In the example shown in Figure 4, not all “Measurement Fidelity” parameters were determined, and the data entered into the table reflects that. If not every parameter is measured, it is still better to report what is known rather than nothing at all. If the AIS is not capable of measuring an “Attribute (Continuous)” type feature, note that fact in the “Measurement Fidelity” column. Again, as with the “Individual Tow Gap” example above, the values shown in Figure 4 are not target value, just examples.

For “Attribute” type features, Bias, Linearity, and Variance will obviously be left blank (or marked as “N/A”) in Column #8.

Closing Remarks The comprehensive list of AFP features discussed in [1] provides a standardized approach to identifying the type and attributes of features and defects commonly experienced during production of aircraft primary structure utilizing the AFP process. NASA and the U.S.

aerospace industry are currently working with US commercial AFP equipment suppliers to address the automated inspection for these features with some success. Currently no AFP equipment supplier is meeting the measurement criteria for all of these features. Therefore, the purpose of this RFI is to collect information from the world-wide aerospace industrial base which informs NASA and our industry partners of the capabilities of existing, or “in-development” AIS with the intention of identifying commercial entities for possible future collaboration.

The extent and accuracy of information provided back to NASA addressing the detection and measurement capability for each of the features identified in Table 1 will significantly enhance NASA’s ability to identify potential partners to develop the AIS technology in the near future. Respondents are encouraged to contact NASA for additional queries.

References

1. Harik, R., Saidy, C., Williams, S., Gurdal, Z., and Brian W. Grimsley;

“AUTOMATED FIBER PLACEMENT DEFECT IDENTITY CARDS: CAUSE,

ANTICIPATION, EXISTENCE, SIGNIFICANCE, AND PROGRESSION,” SAMPE

Conference and Exposition, Long Beach, CA, NASA Report #: NF1676L-29045;

(2018); Link to Publication:

https://ntrs.nasa.gov/api/citations/20200002536/downloads/20200002536.pdf

No solicitation exists; therefore, do not request a copy of the solicitation. If a solicitation is released, it will be synopsized on SAM.gov. Interested firms are responsible for monitoring this website for the release of any solicitation or synopsis.

All responses shall be submitted electronically via email to NASA LaRC Point of Contact (POC) Brian Grimsley, brian.grimsley@nasa.gov, no later than April 30, 2025, at 11:59PM (EST). Please reference: AFP Automated Inspection System in any response.

This synopsis is for information and planning purposes only and is not to be construed as a commitment by the Government nor will the Government pay for information solicited.

Respondents will not be notified of the results of the evaluation.

https://ntrs.nasa.gov/api/citations/20200002536/downloads/20200002536.pdf