WFIRST-IC-SPEC-0068_-.pdf

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National Aeronautics and Space Administration

Goddard Space Flight Center Greenbelt, Maryland

WFIRST-IC-SPEC-0068, Revision -

Wide Field Infrared Survey Telescope (WFIRST), Code 448

Process Specification for Composite Laminate Fabrication

GSFC WFIRST CMO

July 10, 2019

Released

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Destination Country(s): USA ONLY—Export Not Authorized End User: USA Export Commodity Control Number: 9E515.a License/Exemption/Exception Number: N/A

These items are controlled and authorized by the U.S. government for export only to the country of ultimate destination for use by the end-user herein identified.

They may not be resold, transferred, or otherwise be disposed of, to any other country or to any person other than the authorized end-user or consignee(s), either in their original form or after being incorporated into other items, without first obtaining approval from the U.S. government or as otherwise authorized by U.S. law and regulations.

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Process Spec for Comp Lam Fab WFIRST-IC-SPEC-0068, Revision -ii

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Process Specification for Composite Laminate Fabrication

Review/Signature/Approval Page

Prepared by:

Wes Alexander

Approving Signature Authority:

Wes Alexander

Electronic Approval available on-line at: https://ipdtdms.gsfc.nasa.gov iii

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Preface This document is a Wide Field Infrared Survey Telescope (WFIRST) Configuration Management (CM)-controlled document. Changes to this document require prior approval of the applicable Signature Authority or designee. Proposed changes shall be submitted to the WFIRST CM Office (CMO), along with supportive material justifying the proposed change.

In this document, a requirement is identified by “shall,” a good practice by “should,” permission by “may” or “can,” expectation by “will,” and descriptive material by “is.”

Questions or comments concerning this document should be addressed to:

WFIRST Configuration Management Office Mail Stop 448 Goddard Space Flight Center Greenbelt, Maryland 20771 iv

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Change History Log

Revision Effective Date Description of Changes (Reference the Signature Authority Approval Date)

Revision - July 9, 2019 This was approved by the WFIRST Signature Authority via WFIRST-SCoRe-0187 on the effective date shown.

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Table of TBDs/TBRs/TBSs [optional]

Item No. Location Summary Individual/ Organization

Actionee

Due Date vi

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Table of Contents

1 INTRODUCTION

1.1 Purpose

1.2 Scope

1.3 Related Documentation

1.3.1 Applicable Documents [and Forms]

1.3.2 Reference Documents

2 REQUIREMENTS

2.1 Equipment

2.1.1 Autoclaves and Ovens

2.1.2 Work Area

2.1.3 Tools and Fixtures

2.1.4 Contamination Control

2.1.5 Contamination Control Measures

2.1.6 Environmental Controls

2.1.7 Shop Aids and Expendable Materials

2.1.8 Material Handling and Packaging

2.1.8.1 Shelf life and Out Time of Limit Life Materials

2.1.9 Prepreg, Film, and Foam Adhesives

2.1.10 Traceability

2.1.11 Operator and Inspector Training

2.1.12 Process Readiness

2.1.13 Cyanate Ester Resin Processing Precautions

2.1.14 Resin Systems within a Laminate

2.1.15 Layup of Laminate Parts

2.1.15.1 Prepreg Layup Requirements

2.1.15.2 Bleed Schedule Determination

2.1.15.3 Laminate Compaction

2.1.16 Preparation for Cure

2.1.17 Laminate Cure Requirements

2.1.17.1 Cyanate Ester Laminate Cure Cycle

2.1.17.2 Vacuum Ports

2.1.18 Cured Part Handling

2.2 Post Processing Inspection for Laminate Parts

2.2.1 Limits of Acceptability

2.2.2 Part Dimension

2.2.3 Laminate Physical and Mechanical Property Test Requirements

2.2.3.1 Fiber and Void Volume Fraction

2.2.3.2 Laminate Flatwise Tension

2.2.3.3 Laminate Short Beam Shear Strength

3 QUALITY ASSURANCE PROVISIONS AND TEST METHODS

3.1 Prepreg Traceability

3.2 Classification of Tests

3.3 Testing of Production Hardware

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3.4 General Requirements

3.5 Laminate Physical and Mechanical Property Testing

3.5.1 Testing Sampling Requirements for Laminate Parts

3.5.2 Witness Laminate for Laminate Physical and Mechanical Property Testing

3.5.3 Fiber Volume Fraction, Void Volume Fraction, and Density

3.5.4 Laminate Flatwise Tension Strength

3.5.5 Laminate Flexure Strength

3.5.6 Laminate Short Beam Shear Strength

3.5.7 Ply Number and Orientation

3.5.8 Carbamate Testing

The test method of carbamate testing shall be approved by WFIRST

3.5.9 Thermal Strain Measurement

3.6 Non Destructive Testing of Laminate Parts

3.6.1 General

3.6.2 Bake-out/Drying after NDE

3.6.3 Permissible Methods for NDE of Laminate Parts

3.7 Retest

4 PREPARARATION FOR DELIVERY

4.1 Certification Data Requirements

4.2 Identification and Marking

4.3 Packaging

5 NOTES

APPENDIX A ABBREVIATIONS AND ACRONYMS

List of Figures Figure 1. Humidity and Temperature Chart

List of Tables Table 1. Limits for Laminate Parts Table 2. Laminate Fiber Volume fraction Requirements Table 3. Laminate Flatwise Tension Strength requirements Table 4. Laminate Short Beam Shear Strength Requirements Table 5. Laminate Process Control Sampling Requirements

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1 INTRODUCTION

1.1 Purpose

This specification establishes the requirements for composite laminate fabrication for the Wide Field Infrared Survey Telescope (WFIRST). The contractor is responsible for the all requirements within this specification WFIRST-IC-SPEC-0068

1.2 Scope

This specification describes requirements and sets limits of acceptance for fabrication of laminate composite material details and assembled structures for the WFIRST.

1.3 Related Documentation

The latest versions of all documents below should be used. WFIRST documents can be obtained from URL: https://ipdtdms.WFIRST.nasa.gov.

1.3.1 Applicable Documents [and Forms]

The following documents are referenced within this document and are directly applicable or contain policies or other directive matters that are binding for the contents of this document. In the event of conflict between an Applicable Document and the content of this document, the applicable Signature Authority has the final authority for conflict resolution.

In case of conflicting requirements between the requirements of this specification and those noted on the engineering drawing, the drawing’s requirements shall govern

Document Number Title WFIRST-IC-SPEC-0046 Instrument Carrier Flight Structure Fabrication Specification WFIRST-IC-SPEC-0032 Non-Destructive Examination Requirements and Defect

Acceptance Criteria for Non Metallics WFIRST-IC-SPEC-0017 Materials Specification, Preimpregnated Tape WFIRST-SYS-PLAN-0051 WFIRST Contamination Control Plan NAS-410 NAS Certification and Qualification of Nondestructive Test

Personnel

1.3.2 Reference Documents

The following documents are referenced herein and amplify or clarify the information presented in this document. These documents are not binding on the content of this document.

Document Number Title MIL-HDBK-793 Nondestructive Testing Techniques for Structural Composites ASTM E1316 Standard Terminology for Nondestructive Examinations ASTM C 393 Standard Test Method for Flexural Properties of Sandwich

Constructions ASTM D 790 Standard Test Methods for Flexural Properties of Unreinforced and

Reinforced Plastics and Electrical Insulating Material ASTM D 792 Standard Test Method for Density and Specific Gravity (Relative

Density) of Plastics by Displacement

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Document Number Title ASTM D 2344 Standard Test Method for Short-Beam Strength of Polymer Matrix

Composite Materials and Their Laminates ASTM D 3171 Standard Test Methods for Constituent Content of Composite

Materials ASTM D 7291 Standard Test Method for Through-Thickness “Flatwise” Tensile

Strength and Elastic Modulus of a Fiber-Reinforced Polymer Matrix Composite Material

NAS 410 NAS Certification and Qualification of Nondestructive Test Personnel MIL-PRF-131 Barrier Materials, Watervaporproof, Greaseproof, Flexible, Heat-

Sealable

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2 REQUIREMENTS

2.1 Equipment

2.1.1 Autoclaves and Ovens

All processing equipment, such as autoclaves, curing ovens, temperature and pressure recording devices, physical and mechanical test equipment, shall be in a ready-to-use condition and shall be within their current calibration and preventive maintenance cycles. The autoclaves and ovens shall have adequate capacity to properly process the parts, and shall have control equipment capable of maintaining the parts within the temperatures and pressures specified in this specification and the applicable drawing.

Equipment such as autoclaves and ovens shall be demonstrated to meet the requirements of this specification by fabricating test panels prior to use for qualification or flight hardware.

Equipment such as autoclaves and ovens shall be demonstrated to meet the requirements of this specification by fabricating test panels prior to use for qualification or flight hardware.

2.1.2 Work Area

All composite processing work must be performed in environmentally controlled, contamination free areas that meet the temperature and humidity conditions specified in Figure 1. Work areas must be separated from and free of contamination from other shop areas (e.g., through air-handling systems, or adjoining work areas that produce contaminants). The work areas must be visibly clean and free of visible airborne particles, dust and machining residue. Potential contamination sources include silicones, oils and plasticizers. Prior to first use, or if significant facility changes are made, the area shall be checked for cleanliness by Quality Assurance. Work tables and work-in-process shall be covered with a non-contaminating sheet if delays of several hours are anticipated prior to resuming work. The uncured materials shall only be opened and set in environmentally controlled areas that meet manufactures requirements and ISIM requirements. Un-cured materials shall not be moved into controlled areas unless sealed in non-contaminating material or under vacuum.

2.1.3 Tools and Fixtures

All tools, fixtures, and work surfaces shall be kept clean and free from dust, oil, greases, and other surface contaminants. Tooling and fixtures shall be capable of withstanding the temperature and pressure environments during the cure cycle without distortion or other adverse effect on the parts being processed. Tooling and fixtures shall be designed to minimize deformation due to thermal gradients or other thermal effects during the cure, and shall be capable of distributing pressure uniformly over the parts being processed.

2.1.4 Contamination Control

Contamination control is a critical aspect of the fabrication of composite parts and assemblies and must be observed at all times during the process. It applies to materials storage and handling prepreg layup and cure, , bond surface preparation, adhesive bonding, tooling, facility and environmental control, handling, packaging and storage of fabricated parts, and all other steps in the fabrication and assembly process. All laminates and laminate parts shall be delivered

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cleanable to Level 300A per WFIRST-SYS-PLAN-0051. Section 2.1.5 provides a list of common sources of contamination and the measures necessary to prevent them.

2.1.5 Contamination Control Measures

All personnel working with, handling or inspecting composites shall comply with the following precautions:

• Wear protective clean, non-contaminating smocks or coveralls in controlled area

• No hand creams, hair oil, makeup, or similar contaminants in controlled area

• Wear non-contaminating gloves are required in the following situations:

1. In controlled area

2. During bonding operations

3. After parts have been cleaned

• Enter clean room or controlled area through proper entrance.

• Do not circumvent any processes, including cleaning.

• Observe good personal hygiene.

• Do not wear protective clothing outside work area

• Do not use silicone aerosols or other forms of silicone in areas where laminate bonding tools and materials are present or where bonding operations will take place.

• Isolate laminating, bonding and assembly areas from other contamination producing operations and processes. Maintain area cleanliness.

• Use clean containers/materials to store cleaned core, fittings and other parts.

• Cover parts with non-contaminating material during extended breaks.

• Use non-contaminating wipes, Texwipe 609 or equivalent, for wiping cleaned surfaces

2.1.6 Environmental Controls

The areas used for layup of laminates shall be controlled for temperature and humidity per Fig.1, and shall comply with the limits specified by manufacturer.

Records of temperature and humidity in the controlled areas shall be kept during the time that parts are being processed. Temperature and humidity data shall be recorded in the manufacturing planning for the parts being processed.

2.1.7 Shop Aids and Expendable Materials

Non-contaminating gloves are required for layup, surface preparation, assembly, bonding, material handling, and other operations involving the flight materials or materials that will contact the flight materials. Nitrile or powder free latex gloves are required for operations other than acetone wiping. For acetone wiping, polyethylene gloves shall be worn. Acetone will dissolve nitrile or latex gloves and contaminate the surface.

Non-contaminating wipes, Texwipe 609 or equivalent, shall be used for cleaning and wiping operations.

Flashbreaker tapes shall be of the non-contaminating, silicone free adhesive type.

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All expendable materials, which are used in operations involving the flight materials or with materials that will, contact the flight materials, shall be reviewed and approved by the Materials Engineering Branch (MEB) prior to use.

2.1.8 Material Handling and Packaging

Proper handling of the prepreg and adhesive materials is of the utmost importance to prevent excessive outgassing during cure and to ensure the required mechanical properties are achieved in the fabricated parts. It is critically important to prevent the prepreg and adhesive materials from being exposed to moisture.

Material shall be protected from handling damage at all times. Laminates shall be wrapped in protective material, such as non-contaminating plastic film, during storage. Laminates and other parts shall be well supported and shall not be stacked unless previously wrapped or covered in protective material. Laminates shall be transported using appropriate non-contaminating backing materials, to prevent bending and cracking during transport. An acceptable method is cardboard separated from the laminate by non-contaminating plastic film.

Laminates and other composite parts shall be labeled to maintain traceability to the original raw material and cure process. If a permanent label or marking are used, the label material, marking method, and location shall be per the appropriate engineering drawing.

Material shall be protected from knocks, kicks, dropped objects, and other potential damage.

Any material that is subjected to any percussive, excessive bending or dropping event shall be tagged for NDE inspection

2.1.8.1 Shelf life and Out Time of Limit Life Materials

Shelf life materials used in assemblies, including pre-impregnated tape and fabric, paste adhesive, and other limited life materials shall be within their shelf life (time at storage temperature) as defined by the applicable material or procurement specification, and shall be within the manufacturers out time (time at room temperature) limits. The shelf life and out times of these materials shall be tracked in an out time log and their status checked prior to use. The materials shall be within their specified shelf life and out time up to the time of cure.

Shelf life requirements shall be reviewed and approved by the MEB.

Re-qualification of shelf life materials after expiration of shelf life or out time is subject to the approval of the MEB.

2.1.9 Prepreg, Film, and Foam Adhesives

Prepreg, film, and foam adhesives materials shall be packaged in a contamination free, moisture proof bagging material per the requirements of specification MIL-PRF-131. The package shall be tightly sealed to prevent moisture entrapment and, when possible, a packet of non-contaminating desiccant shall be placed inside the package.

All frozen prepregs and adhesives shall be brought to room temperature in an area meeting the temperature and relative humidity requirements of Figure 1 before opening the sealed package.

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The moisture proof package shall not be opened at any time, including when initially received from the supplier, before the material has reached room temperature. These precautions are necessary to prevent moisture contamination in the prepreg and adhesive materials. The outer surface of the package shall be free of moisture condensation before opening the package. If condensation is present, the material shall remain unopened until all condensation has disappeared. If the prepreg or adhesive materials will not be used within 48 hours after reaching room temperature, it is recommended that the materials shall be repackaged and returned to the freezer. If the material will not be used for a period greater than several hours, it is recommended that the material be covered with a non-contaminating material to prevent contamination.

Prior to returning unused material to the freezer, the moisture proof package shall be purged with dry gas, if possible, and tightly sealed with flashbreaker (or equivalent) tape or heat sealed. A log sheet recording the material out-time shall be maintained for each roll or container of prepreg and adhesive material.

2.1.10 Traceability

Traceability information shall be maintained and shall be recorded on the manufacturing traveler for all materials and parts that become part of the fabricated assembly

2.1.11 Operator and Inspector Training

Operators and inspectors involved in fabrication and testing of parts controlled by this specification shall be qualified by a formalized training program and experience in the specific skills required. In addition, operators and inspectors shall be qualified to perform special processes, including prepreg layup, adhesive mixing and bonding, potting, and chemical surface preparation, through process-specific training. Inspectors performing NDE testing shall be Level II or Level III certified per NAS 410.

2.1.12 Process Readiness

All critical processes used for fabrication of flight hardware shall have demonstrated a complete process readiness, including a demonstration of capability to meet the stated engineering requirements through inspection and acceptance testing. This includes but is not limited to:

1. equipment readiness

2. process and procedure documentation, including manufacturing planning/travelers and standard processes, as designed versus as built

3. tooling

4. facilities

5. test methods

6. training of operators and inspections

7. destructive evaluation, including sectioning and microscopic examination, of specific parts, including laminates and structural shapes

8. results of demonstration testing as approved by the MEB

Process readiness for flight hardware fabrication shall be demonstrated via a formal review unless otherwise specified in the statement of work. The detailed manufacturing instructions and other process readiness information as defined above shall be reviewed by the WFIRST MEB and designated Engineering and Quality Assurance personnel

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2.1.13 Cyanate Ester Resin Processing Precautions

The performance of cyanate ester materials is adversely affected by moisture and/or metal catalysts. Such negative effects include difficulty in subsequent bonding operations or blisters or ply separations within the laminate. Precautions are especially critical for the release or peel ply and resin bleeder layers utilized during laminate cure. It is therefore critical that the process materials utilized in fabricating cyanate ester resin laminates be carefully selected to have low moisture absorbing characteristics. Materials used in processing of cyanate ester laminates shall be reviewed and approved by the MEB. Use of graphite/epoxy slip sheets shall be prohibited.

Release ply and peel ply materials with release materials containing metal catalysts may also react with the cyanate ester resin. Nylon peel ply or bleeder materials are not permitted when processing cyanate ester materials. Polyester peel plies have also been shown to absorb moisture but at a lower level. If polyester materials are used in the processing of cyanate ester resins, precautions shall be made to sufficiently dry out the materials prior to contact with uncured cyanate ester resin prepreg. This can be accomplished by baking the materials a minimum of one of the following:

• four hours at 150 °F (66°C)

• two hours at 250°F (121°C)

• one hour at 350 °F (177°C) within one week of layup. Following bakeout, the processing materials shall be protected from absorbing moisture by packaging in aluminized polyester or other non-contaminating non-porous material and remaining sealed until use. If there is any indication or concern that the processing materials may have absorbed moisture, the bakeout process shall be repeated.

To ensure that moisture has been sufficiently removed from the uncured cyanate ester laminate and process materials, the laminate shall be held under vacuum for 8 hours minimum prior to application of heat.

2.1.14 Resin Systems within a Laminate

Unless specified on the engineering drawing, for laminates with multiple material types, the resin system for each material shall be the same for all materials in the laminate.

2.1.15 Layup of Laminate Parts

2.1.15.1 Prepreg Layup Requirements

Tools shall be inspected prior to use for dents, scratches or surface imperfections. Any significant defects shall be repaired prior to tool use.

Mold release Frekote 700-NC is approved for use after proper application. Application of mold release shall be performed in an area that is environmentally isolated from the area(s) used for composite layup. The mold release shall be completely cured prior to use.

Prepreg shall be handled per 2.1.8. Non-contaminating gloves per 2.1.7 shall be worn at all times when handling prepreg.

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For flat laminates, a layer of Teflon release cloth shall be used between the layup table and the laminate. Silicone treated cloth is not permitted. For other parts such as angles, channels, and other structural shapes, either a layer of Teflon release cloth or non-contaminating flashbreaker tape shall be used between the tool and the laminated part.

Care shall be taken to prevent release paper, tapes, or any other foreign materials from being incorporated into the laminate.

Joints between pieces of a ply shall be kept a minimum of 1 inch away from similar joints in other plies that have the same ply angle. If ply joints need to be staggered at less than 1 inch because of scrap or configuration prior approval will be required by WFIRST MEB. No ply joints shall be parallel and directly up on top of another within 2 ply stacks in a lay-up. Ply stacks are defined on each drawing.

Wrinkles and air entrapment shall be minimized during the layup. It is recommended to debulk each ply or to carefully roll the material with a non-contaminating roller or similar device, taking care not to damage the material.

Prepreg splices shall be minimized. Where the drawing states the fabric ply angle as 0/90, either 0 degree or 90 degree orientation of the material relative to the 0 degree reference axis is permissible.

2.1.15.2 Bleed Schedule Determination

Bleed schedule, i.e. number and type of bleeder material to be used for laminate cure, is to be verified for each lot of prepreg material and/or layup configuration prior to fabrication of flight or qualification laminates. This determination must verify that the laminate fiber volume will meet the requirements specified herein.

2.1.15.3 Laminate Compaction

During layup, the first ply of the laminate, followed by the laminate layup every three plies, shall be compacted by application of vacuum and/or pressure. More frequent compaction may be required to achieve the requirements of this specification, depending on part size, shape, and number of plies. It is recommended that vacuum of 20 inches Hg minimum or total pressure of 100 psi maximum be held for a minimum of 5 minutes for each compaction step. It is permissible to heat the tool to 100 degrees F maximum to facilitate layup.

2.1.16 Preparation for Cure

The laminate shall be held under vacuum for 8 hours minimum prior to application of heat.

2.1.17 Laminate Cure Requirements

Prior to processing of flight or qualification laminates, at least one temperature profile run with the same tooling and monitoring configuration shall be performed to verify that the specified cure requirements will be met.

2.1.17.1 Cyanate Ester Laminate Cure Cycle

The cure cycle for 954-6 prepreg is based on Hexcel’s HPC-4 cure cycle and results in a degree of cure from 80% to 85%. The cycle is:

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1. Apply 22-28 in. Hg vacuum to a vacuum bag and 50 psig positive pressure in an autoclave

2. Ramp 1ºF to 4ºF per minute to 265ºF ±5ºF

3. Hold at 265ºF ± 5ºF for 190 minutes to 205 minutes

4. Release pressure and vent vacuum

5. Cool down at 5ºF per minute maximum to 140ºF or less, remove part

2.1.17.2 Vacuum Ports

Vacuum gauges shall be placed and connected such that they measure the vacuum applied to the part though-out the cure cycle and such that they detect any variations in apparent vacuum due to bag failure, breather crushing, or other effects.

A minimum of two vacuum ports shall be used. Additional vacuum ports shall be used as required to ensure proper compaction, depending on the size of the part(s) being cured.

A vacuum leak check shall be performed prior to application of heat.

2.1.18 Cured Part Handling

Cured laminated parts shall be stored in protective containers that rigidly protect the part.

Composite parts may be fragile and are easily damaged. Care shall be taken to avoid contact with sharp edges of parts that could cause part damage or personnel injury. Cured tubes and laminate face-sheets shall be handled and stored so that they remain flat within approximately 1 inch per 24 inches of span.

2.2 Post Processing Inspection for Laminate Parts

Laminated parts shall be 100% visually inspected and shall show no signs of fractured fibers, delaminated plies, missing or loose fibers, or dents. Surface scratches or gouges shall not be greater than 0.5 inch long, 0.05 inch wide and one ply thickness deep. There shall be no scratches or gouges in laminates or detail parts penetrating the surface resin layer within 2 inches of areas where parts will subsequently be bonded. There shall be no wrinkles greater than 0.003 inches in height or depth. There shall be no visual evidence of foreign material inclusions such as dirt or metallic shavings exceeding a dimension of 0.125 inch in length, with no more than one such inclusion in six linear inches of composite. Delaminated or poorly consolidated areas shall be cause for rejection of the laminated part.

2.2.1 Limits of Acceptability

Each fabricated laminate, or as applicable, representative laminate, as defined in 3.5.1, shall be tested and meet the requirements specified in Table 1. Sampling requirements for laminate testing are specified in paragraph 3.5.1.

Table 1. Limits for Laminate Parts

Characteristics Limits Test Paragraph

Comment

Ply Orientation Per Engineering Drawing 3.5.7 On actual laminate of part

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Characteristics Limits Test Paragraph

Comment

Fiber Volume Fraction % Void Volume Fraction %

FV 60 ± 3% VC < 2% 2.3.3 On actual laminate or part and witness laminate, if applicable

Density Report 2.3.3 On actual laminate or part and witness laminate, if applicable

Visual Appearance Pass/ Fail 2.2 On Actual laminate or part per 3.7.3

Non- Destructive Evaluation

WFIRST-IC-SPEC-0032

Type I II

On actual laminate or part per 3.7.3

Flat wise Tension Testing

Table TBD

Short Beam Shear Table TBD X,Z Laminate 0° Thermal Strain

Cool down Strain (X- ) from 293 to 170K =TBD ± 10 ppm

Laminate 90°Thermal Strain

Cool down Strain (Y- Direction) from 293 to 170K =TBD ± 10 ppm

2.2.2 Part Dimension

The Parts shall be measured and shall meet the requirements of the engineering drawing.

2.2.3 Laminate Physical and Mechanical Property Test Requirements

2.2.3.1 Fiber and Void Volume Fraction

Each fabricated laminate, or as applicable, representative laminate, as defined in 4.5.1, shall be tested and meet the requirements specified in Table 2. Sampling requirements for laminate testing are specified in paragraph 4.5.1.

Table 2. Laminate Fiber Volume fraction Requirements

Laminate Type Material Specification

Fiber Volume Fraction%

Void Volume Fraction %

M55J/954-6 Unidirectional Tape

WFIRST-IC-SPEC-

0017-01

60 ± 3 <2%

T300 Tape WFIRST-IC-SPEC- 0017-02

60 ± 3 <2%

T300 Fabric TBD TBD <2%

2.2.3.2 Laminate Flatwise Tension

Laminate flatwise tension strength shall be measured on each fabricated laminate or witness laminate, as applicable. The requirements shall be per Table 3 after conditioning laminate billets from 293K to 170K 5cycles (TBR).

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Table 3. Laminate Flatwise Tension Strength requirements

Laminate Type Material Specification Flatwise tension Strength Minimum Average, psi

M55J/954-6 Unidirectional Tape

WFIRST-IC-SPEC-

0017-01

TBA

T300 Tape WFIRST-IC-SPEC- 0017-02

TBA

T300 Fabric TBD TBD

2.2.3.3 Laminate Short Beam Shear Strength

Laminate short beam shear strength shall be measured on each witness laminate, as applicable.

Laminate flexure strength shall meet the requirements of Table 4.

Table 4. Laminate Short Beam Shear Strength Requirements

Laminate Type Material Specification Short Beam Shear Strength Requirement Minimum Average.

Ksi

M55J/954-6 Unidirectional Tape

WFIRST-IC-SPEC-

0017-01

TBA

T300 Tape WFIRST-IC-SPEC- 0017-02

TBA

T300 Fabric TBD TBD

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3 QUALITY ASSURANCE PROVISIONS AND TEST METHODS

Unless otherwise specified herein or in the contract or purchase order, the material supplier is responsible for the performance of all inspection and testing specified herein. Individual and average data results shall be reported. Unless otherwise specified herein, the average result must meet the specified limit(s). The test methods specified herein shall be used unless specifically pre-approved by WFIRST.

Testing shall be performed at room temperature (75±5°F) and less than 80% relative humidity unless otherwise specified herein or in the applicable test specification. Test equipment used shall be calibrated in accordance with the applicable test specifications.

3.1 Prepreg Traceability

Materials and process history information is required with each part fabricated to this specification. This information shall include, but not be limited to, the following:

a. Identification of the prepreg used, including the vendor lot number and the vendor roll number.

b. Prepreg vendor certification data on the prepreg lot

c. Part processing parameters including dates, times, layup area temperature and humidity data, and cure/bonding cycle conditions, including strip chart or computer data records for temperature, pressure and vacuum.

3.2 Classification of Tests

Inspection and acceptance testing shall be performed on both process development and production laminated parts. Inspection shall consist of the visual inspection of in-process hardware and the visual inspection and non-destructive testing of completed hardware.

Acceptance testing shall be conducted on the fabricated hardware or samples representing the completed hardware as defined herein.

3.3 Testing of Production Hardware

Non-destructive testing shall be performed on all process development and flight parts and assemblies.

Destructive testing shall be performed on process control samples as defined herein. If unacceptable test results are obtained within a lot of fabricated parts, the production parts fabricated since the last acceptable production lot shall be quarantined and subject to Re-inspection. The cause of the defect(s) and the required corrective action shall be determined.

The corrective action shall include testing as required to ensure that the defect will not reoccur and, if applicable, the testing necessary to ensure that the quarantined parts are not affected by the observed defect.

3.4 General Requirements

Mechanical property testing shall be performed at room temperature unless otherwise specified in this specification.

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For mechanical property testing, photographs shall be taken to document the test configuration and failure modes of all specimens. Photograph filenames shall include identification by specimen ID. Test reports shall include the information specified in the referenced test specifications and any information specified herein. Test reports shall be included in the end item data package.

3.5 Laminate Physical and Mechanical Property Testing

3.5.1 Testing Sampling Requirements for Laminate Parts

Sampling requirements for laminated parts shall be per Table 5. The sampling requirements apply to samples with valid test result. Sufficient spare coupons shall be fabricated to ensure to the required number of valid test results are obtained. For cures with multiple laminates of the same or similar parts, it is permissible to perform process control testing other than fiber and void volume fraction on a minimum of one set of samples for each type of part, bleed (bagging) scheme, material lot, and vacuum bag configuration. Vacuum bag configurations defined as all vacuum bags connected to a source that would be compromised if seal is lost on one of the vacuum bags. Material lot includes all rolls of material from a material lot. The intent is to assure that the process control specimens accurately represent the configuration being represented. The process control samples shall be from either a fabricated part or a witness laminate as defined in Table 5.

For parts where a blank laminated part is fabricated, the process control testing requirements may apply to the blank.

Types of parts are defined as follows:

1) Face-sheet laminate with specific layup/number of plies

2) Thick fabric laminate of specific layup/number of plies

3) L-clip of specific layup/number of plies

4) Other parts such as gussets with specific layup/number of plies

The default requirement is fiber and void volume fraction testing for a minimum of one representative sample for each fabricated part or blank (as defined by part or blank part drawing number) per vacuum bag configuration. For cures involving multiple parts with the same configuration, it is recommended that correlation between fiber and void volume and another measurable parameter, such as part thickness, be developed to ensure consistency within the lot.

It should be shown that the allowable range of the measured parameter (i.e. thickness) is sufficient to ensure that all other characteristics of the part, including dimensions and physical properties, are met. Alternate sampling for process control testing requires prior approval of the

MEB.

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Table 5. Laminate Process Control Sampling Requirements

Fabricated Part representing lay-up

Fiber Volume Fraction, Void Volume Fraction, density

Laminate Flatwise Tension Strength

Laminate Flexure Strength

Laminate Short Beam Shear Strength

3 *Note 1 3 *Note 1 3 *Note 1 3 *Note 1 3 *Note 1 3 *Note 1 3 *Note 1 3 *Note 1 3 *Note 1 3 *Note 1 3 *Note 1 3 *Note 1 3 *Note 1 3 *Note 1 3 *Note 1

* 1 Note: These are minimum test specimen numbers

3.5.2 Witness Laminate for Laminate Physical and Mechanical Property Testing Samples from a witness laminate may be used in place of samples cut from the fabricated part for parts made from fabric prepreg material, including the following:

a) Structural shapes, other than flat laminates, such as angle clips and tubes

b) Thick fabric laminates with thickness greater than 0.10 inch Applicability of the witness laminate for different part types is defined in Table 5.

3.5.3 Fiber Volume Fraction, Void Volume Fraction, and Density Fiber volume fraction and void volume fraction for cured laminates shall be determined per ASTM D 3171. Two samples minimum are required per tested configuration. The reported values shall be an average of samples taken at a specific location. The size of the samples shall be 1 gram minimum (per ASTM D 3171) unless an alternate sample size has been demonstrated to produce consistent results. Density of the laminate shall be measured per ASTM D 792.

Laminate density is a reference value and shall be calculated whenever fiber volume fraction is measured. It is recommended that samples be taken in appropriate area(s) of the laminate, i.e.

sufficiently far from the cured edge, such that edge effects do not affect the results.

3.5.4 Laminate Flatwise Tension Strength

Laminate flatwise tension shall be performed using ASTM D7291, with additional details of specimen configuration and testing provided by WFIRST. The laminate shall be bonded to the test blocks using an appropriate adhesive. It is recommended that a room temperature cure adhesive with high peel strength, such as EA9309.3 or 9309.2 with 5 mil bond beads, Care shall be taken to align the loading blocks with respect to each other and to the laminate during bonding.

Specimen failure should not occur in the laminate-to-load block bonds. Care shall be taken to minimize bending and edge effects that will decrease the strength of the specimen. Test machine crosshead rate shall be .05 inches per minute or as specified by WFIRST. Failure mode of the specimen shall be described in the test report.

3.5.5 Laminate Flexure Strength

Laminate flexure testing shall be performed per ASTM D 790, with additional details of specimen configuration and testing provided by WFIRST. Failure mode of the specimen shall be described in the test report.

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3.5.6 Laminate Short Beam Shear Strength

Laminate short beam shear strength testing shall be performed per ASTM D 2344. Failure mode of the specimen shall be described in the test report.

3.5.7 Ply Number and Orientation

The number and orientation of plies in laminated parts shall be verified to meet the requirements of the engineering drawing. Verification shall be performed either by sectioning and microscopic inspection, or by in-process inspection with independent verification.

3.5.8 Carbamate Testing

The test method of carbamate testing shall be approved by WFIRST.

3.5.9 Thermal Strain Measurement

The test method of thermal Strain measurement shall be approved by WFIRST.

3.6 Non Destructive Testing of Laminate Parts

3.6.1 General

The methods used for non-destructive testing shall be consistent with the requirements WFIRST- IC-SPEC-0032. The test methods shall be capable of detecting the defects specified in WFIRST- IC-SPEC-0032 or, as applicable, Section 3 of this document. The following methods are recommended. Alternate methods will be considered per the provisions of WFIRST-IC-SPEC- 0032.

3.6.2 Bake-out/Drying after NDE

Laminates and assemblies must be baked out if water-coupled C-scan NDT is performed.

For laminates, the minimum bake-out after water-coupled C-scan shall be 2 hours at 185 +10/-0 °F (85 +6/-0 °C

For local A-scan NDT using water couplant, laminate surfaces shall be dried after testing prior to final cleaning. Acceptable drying methods are:

a) Blow dry using bottled, clean dry nitrogen

b) Oven dry at 150 °F (66 °C) for 2 hours minimum

3.6.3 Permissible Methods for NDE of Laminate Parts

The default method for NDE inspection of laminated parts is NDT per WFIRST-IC-SPEC-0032, as applicable on the finished part after machining.

For laminated parts where the part is machined from a blank laminate or structural shape, an alternate method of NDE inspection may be performed with prior approval of the MEB. This alternate method consists of both of the following:

a) NDE inspection of the blank laminate or structural shape per WFIRST- IC-SPEC-0032 prior to final machining of detail part.

b) Complete visual inspection of the part after final machining using 3x minimum magnification and an isopropyl alcohol wipe to highlight delaminations.

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The specific plan for implementation of the alternate method shall be submitted for approval.

3.7 Retest

If the test results do not comply with the requirements of Section 3, the material may be retested using the original number of samples. If the second set of tests does not meet the specified requirements, the item shall be considered discrepant and shall be processed through MRB.

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4 PREPARARATION FOR DELIVERY

4.1 Certification Data Requirements

Certification data substantiating that the material meets the requirements of this specification shall be supplied with the material. The end item data package logbook shall show the lot and batch numbers and the date of manufacture for material traceability, material certification data, test data, configuration verification data, and other information as required to verify that the fabricated part(s) meet the requirements of this specification.

The supplier shall submit three copies of the end item data package, with all required production test results, including average and individual values for each specimen, to demonstrate that the material submitted for approval meets the requirements of this specification. One copy shall be submitted with the shipment, one copy sent to the WFIRST Product Assurance Department, and one copy sent to the WFIRST MEB. If WFIRST is not the direct procuring activity, a copy shall also be sent to the Quality Control Department of the procuring activity.

4.2 Identification and Marking

The drawing and serial numbers of the part(s) or panel(s) shall be indicated on each part or panel or their container as specified on the engineering drawing. Drawing and serial numbers shall be re-marked, as required, to preserve a previous marking that has become obscured or obliterated.

4.3 Packaging

Parts and panels shall be handled, transported and stored in such a manner that they shall remain capable of meeting the requirements of this specification. Parts and panels shall be provided with protective covering at all times except as necessary for fabrication or inspection processes.

Panels and parts shall be transported or stored only in a protective container and shall be removed from the container only as necessary for fabrication and inspection processes.

Unprotected structures should be placed flush against a clean flat surface. The part or panel assembly shall be suitably packaged to prevent any contamination or damage in transport or storage. Panels shall be supported and protected in a structural crate such that transportation loads and environments have no deleterious effects on the assembly and detail panels.

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5 NOTES

Figure 1. Humidity and Temperature Chart

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Appendix A Abbreviations and Acronyms

Abbreviation/ Acronym

DEFINITION

NDE Non-Destructive Inspection TBA To be assessed TBD To Be Determined TBR To Be Revised TBS To Be Scheduled WFIRST Wide Field Infrared Survey Telescope

2.1.18 Cured Part Handling

3.7 Retest