WFIRST-IC-SPEC-0017A.pdf

Effective Date: July 12, 2019 Expiration Date: July 12, 2024

CHECK https://ipdtdms.gsfc.nasa.gov

TO VERIFY THAT THIS IS THE CORRECT VERSION PRIOR TO USE.

National Aeronautics and Space Administration

Goddard Space Flight Center Greenbelt, Maryland

WFIRST-SPEC-16491, Revision A

Wide Field Infrared Survey Telescope (WFIRST), Code 448

Material Specification, 954-6 Preimpregnated Tape

GSFC WFIRST CMO

July 12, 2019

Released https://ipdtdms.gsfc.nasa.gov/

Material Spec, 954-6 Preimpregnated Tape WFIRST-SPEC-16491, Revision A ii

Material Specification, 954-6 Preimpregnated Tape

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

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

Change History Log

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

Revision - April 9, 2019 Initial release per WFIRST-CIR-09549 Revision A July 12, 2019 This was approved by the WFIRST Signature Authority via WFIRST-SCoRe-0217 on the effective date shown.

v

Table of TBDs/TBRs/TBSs [optional]

Item No. Location Summary Individual/ Organization

Actionee

Due Date vi

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

1.4 Document Precedence

2 REQUIREMENTS

2.1 General

2.1.1 Resin

2.1.2 Reinforcement Fiber Requirements

2.1.2.1 Unidirectional Tape, (-01, material)

2.1.2.2 Unidirectional Tape, (-02 material)

2.1.2.3 Fiber Certification Data

2.2 Uncured Material Properties

2.2.1 Physical Property Testing

2.2.2 Differential Scanning Calorimetry

2.2.3 IR Analysis

2.3 Cured Material Properties

2.4 Workmanship Requirements

2.4.1 Appearance

2.4.2 Unidirectional Tape Workmanship Requirements

2.4.2.1 Gaps

2.4.2.2 Splices

2.4.2.3 Fiber Straightness

2.4.2.4 Fiber Balls

2.4.2.5 Prepreg Pucker

2.4.2.6 Width

2.4.3 Tack

2.4.4 Liners

2.4.5 Out Time

2.4.6 Shelf Life

2.5 Nonconforming Material

2.6 Material Handling

3 QUALITY ASSURANCE PROVISIONS AND TEST METHODS

3.1 Sampling

3.1.1 Prepreg Lot/Batch

3.1.2 Fiber Lot

3.1.3 Deleted

3.1.4 Resin Batch

3.1.5 Uncured Material Physical Property Test Sampling

3.1.6 Mechanical Property Test Sampling

3.2 Physical Property Test Methods

vii

3.2.1 Fiber Areal Weight and Resin Content

3.2.2 Fiber Volume Fraction and Void Content

3.2.3 Volatile Content

3.2.4 Resin Flow

3.2.5 Gel Time

3.2.6 Glass Transition Temperature

3.2.7 Cured Ply Thickness

3.2.8 Prepreg Visual Tests

3.2.8.1 Evaluation for Puckers

3.2.9 Tack

3.2.10 Thickness Variability

3.3 Mechanical Property Test Methods

3.3.1 Tensile Testing

3.3.2 Compression Testing

3.3.3 Short Beam Shear Testing

3.4 Retest

3.5 Requalification After Expiration of Shelf Life

4 PREPARATION FOR DELIVERY

4.1 Certification Data Requirements

4.2 Packaging

4.3 Temperature Monitoring

4.4 Material Identification Labeling

5 NOTES

5.1 Intended Use

5.2 Ordering Data

5.3 Sources of Supply

APPENDIX A ABBREVIATIONS AND ACRONYMS

List of Figures Figure 1. Prepreg Handling and Processing Area Environment Figure 2. Prepreg Variability Measurement

List of Tables Table 1. Uncured Material Properties, Class-01, M55JB/954-6 Tape (Net Resin System) Table 2. Uncured Material Properties, Class-02, T300/954-6 Tape (net Resin System) Table 3. Cured, Unidirectional Tape Laminate Property Requirements for Purchase Acceptance

Classification -01 Table 4. Cured Unidirectional Tape Laminate Property Requirements for Purchase Acceptance

Classification-02 Table 5. Mechanical Property Sampling Plan

1 INTRODUCTION

1.1 Purpose

This Specification (SPEC) defines those requirements necessary to procure, test, and qualify material used on WFIRST.

1.2 Scope

This specification describes the requirements and sets limits of acceptance for adhesive bonding of composite material, metallic details and assembled structures for the Instrument Carrier (IC) Structure

1.3 Related Documentation

The latest versions of all documents below should be used. WFIRST documents can be obtained from URL: https://ipdtdms.gsfc.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 WFIRST Project Configuration Change Board (CCB) has the final authority for conflict resolution.

Document Number Title MIL-T-29586 Military Specification, Thermosetting Polymer Matrix, Unidirectional Carbon Fiber Reinforced Prepreg Tape (Widths up to 60 inches), General Specification For (30-APR-1991)

MIL-PRF-131 Barrier Materials, Water vapor proof, Greaseproof, Flexible, Heat- Sealable

ASTM C 61 Standard Test Method for Constituent Content of Composite Prepreg by Soxhlet Extraction

ASTM D 695 Standard Test Method for Compressive Properties of Rigid Plastics ASTM D 2344 Standard Test Method for Short-Beam Strength of Polymer Matrix

Composite Materials and Their Laminates ASTM D 2734 Standard Test Methods for Void Content of Reinforced Plastics ASTM D 3039 Standard Test Method for Tensile Properties of Polymer Matrix

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

Materials ASTM D 3529 Standard Test Method for Matrix Solids Content and Matrix Content of Composite Prepreg ASTM D 3530 Standard Test Method for Volatiles Content of Composite Material

Prepreg ASTM D 3531 Standard Method for Resin Flow of Carbon Fiber-Epoxy Prepreg ASTM D 3532 Standard Method for Gel Time of Carbon Fiber-Epoxy Prepreg SACMA SRM-1 Compressive Properties of Oriented Fiber-Resin Composites

Document Number Title SACMA SRM-8 Apparent Interlaminar Shear Strength of Oriented Fiber-Resin

Composites by the Short-Beam Method ASTM E1640 Standard Method for Glass Transition Temperature by Dynamic

Mechanical Analysis

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 None

1.4 Document Precedence

In the event of a conflict between this specification, the engineering drawing, and any other specification cited herein, the requirements of this specification shall prevail.

2 REQUIREMENTS

2.1 General

2.1.1 Resin

The resin shall be a cyanate ester polymer capable of meeting the requirements of this specification when reinforced with carbon filaments, designated as Hexcel 954-6, as specified in Tables 1 through 11.

2.1.2 Reinforcement Fiber Requirements

The fiber shall be a high stiffness carbon fiber capable of meeting the requirements of this specification when impregnated and processed with the resin specified herein. It shall include controlled surface treatment (sizing) to facilitate bonding to the resin. The reinforced fibers shall have the following characteristics

2.1.2.1 Unidirectional Tape, (-01, material).

Fiber type: M55JB (manufacturer: Toray) Tow Size: 6000 (6K) Twist: None

2.1.2.2 Unidirectional Tape, (-02 material).

Fiber Type: T300 (manufacturer Cytec) or T300B (manufacturer Toray) Tow Size: 3000 (3K) Twist: Cytec T300: never twisted; Toray T300B: untwisted

2.1.2.3 Fiber Certification Data.

Fiber certification data shall be provided as part of the material certification data package. The fiber certification data shall include fiber lot mean and, if available, standard deviation for fiber strength and modulus.

2.2 Uncured Material Properties

2.2.1 Physical Property Testing

Required physical property testing for the uncured prepreg materials are specified in Tables 1 and 2.

Table 1. Uncured Material Properties, Class-01, M55JB/954-6 Tape (Net Resin System)

Property (Room Temp.)

Requirements of Class A material

(Notes 1 & 2)

Requirements of Class B material

(Notes 1 & 2)

Number of Samples Test Paragraph

Fiber Areal Weight (gm/m2) 81.5±3 81.5± 3 Note 3 3.2.1

Resin Content (weight %) 31.5±1 31.5± 2 Note 3 3.2.1

Volatile Content (weight %) 2 Maximum 2 maximum 3 3.2.3 Resin Flow @100psi, 121°C

(percent) 8 to 18 8 to 18 3 3.2.4

Requirements of Class A material

(Notes 1 & 2)

Requirements of Class B material

(Notes 1 & 2)

Number of Samples Test Paragraph

Resin Gel Time @ 121°C (minutes) 10 to 35 10 to 35 3 3.2.5

Tack Pass Pass 3 3.2.9

Fiber Strength and Modulus Report Report NA NA Thickness Variability (inches)

(max. thickness – min.

thickness)

.0003 or less 0.0003 or less across the web 3.2.10

Notes:

1) See sampling plan, Paragraph 3.1, for required rolls to be tested.

2) Requirement applies to average test values.

3) 3 tests across the web at the beginning and end of a roll.

Table 2. Uncured Material Properties, Class-02, T300/954-6 Tape (net Resin System)

Requirements of Class A material

(Notes 1&2)

Requirements of Class B material

(Notes 1 & 2)

Number of Samples Test Paragraph

Fiber Areal Weight (gm/m2) 75.5± 2 75.5 ± 2 Note 3 3.2.1

Resin Content (weight %) 33± 1 33± 2 Note 3 3.2.1

Volatile Content (weight %) 2 Maximum 2 maximum 3 3.2.3 Resin Flow @100psi, 121°C

(percent) 8 to 18 8 to 18 3 3.2.4

Resin Gel Time @ 121°C (minutes) 10 to 35 10 to 35 3 3.2.5

Tack Pass Pass 3 3.2.9

Fiber Strength and Modulus Report Report report NA Thickness Variability (inches)

(max. thickness – min.

thickness)

.0003 or less 0.0003 or less across the web 3.2.10

Notes:

1) See sampling plan, Paragraph 3.1, for required rolls to be tested.

2) Requirement applies to average test values.

3) 3 tests across the web at the beginning and end of a roll.

2.2.2 Differential Scanning Calorimetry

Differential Scanning Calorimetry (DSC) analysis shall be performed and shall be reviewed for consistency with previously qualified lots. DSC analysis shall be retained on file and available for review by the purchaser upon request.

Note: Specific ramp rate @20°C/min from room temperature to 400° C.

2.2.3 IR Analysis

An IR scan shall be performed on resin used in the prepreg and shall be reviewed for consistency with previously qualified lots. IR scan traces shall be retained on file and available for review by the purchaser upon request.

2.3 Cured Material Properties

Required physical and mechanical property testing for the cured prepreg material is specified in Table 3 for unidirectional tape (-01), and Table 4 Unidirectional T300 (-02).

Table 3. Cured, Unidirectional Tape Laminate Property Requirements for Purchase Acceptance Classification -01

Property (Room Temp.) Requirement Number of

Samples Test Paragraph

0° Tensile Modulus Avg. Value, Minimum (psi) Single Value, Minimum (psi)

36.7x106 33x106 5 3.3.1

0° Tensile Strength Avg. Value, Minimum (psi) Single Value, Minimum (psi)

240x103 204x103 5 3.3.1

0° Compressive Modulus Avg. Value, Minimum (psi) Single Value, Minimum (psi)

33.7x106 30.3x106 5 3.3.2

0° Compressive Strength Avg. Value, Minimum (psi) Single Value, Minimum (psi)

102x103 86.7x103 5 3.3.2

0° Short-Beam Shear Strength Avg. Value, Minimum (psi) Single Value, Minimum (psi)

9.0x103 8.5x103 5 3.3.3

Glass Transition Temperature, (°C) (Report) 2 3.2.6

Cured Ply Thickness (mils) @60% Fiber Volume

2.8±0.3

Ten Measurements per each SBS panel 3.2.7

Notes:

1) See sampling plan, Paragraph 3.1, for required rolls to be tested.

2) All properties except short-beam shear strength shall be normalized to 60% fiber volume.

3) Cure I.A.W Hexcel cure cycle HSP-C4 (per 3.1.6) with final hold temperature 265±100F for 190 to 205 minutes.

Table 4. Cured Unidirectional Tape Laminate Property Requirements for Purchase

Acceptance Classification-02

Property (Room Temp.) Requirement Number of

Samples Test Paragraph

0° Tensile Modulus Avg. Value, Minimum (psi) Single Value, Minimum (psi)

18.5x106 17.5x106 5 3.3.1

0° Tensile Strength Avg. Value, Minimum (psi) Single Value, Minimum (psi)

250x103 230x103 5 3.3.1

0° Compressive Modulus Avg. Value, Minimum (psi) Single Value, Minimum (psi)

18.0x106 17.0x106 5 3.3.2

0° Compressive Strength Avg. Value, Minimum (psi) Single Value, Minimum (psi)

180x103 170x103 5 3.3.2

0° Short-Beam Shear Strength Avg. Value, Minimum (psi) Single Value, Minimum (psi)

10x103 9.5x103 5 3.3.3

Glass Transition Temperature, (°C) (Report) 2 3.2.6

Cured Ply Thickness (mils) @60% Fiber Volume (Report)

Ten Measurements per each SBS panel 3.2.7

Notes:

1) See sampling plan, Paragraph 3.1, for required rolls to be tested.

2) All properties except short-beam shear strength shall be normalized to 60% fiber volume.

3) Cure I.A.W Hexcel cure cycle HSP-C4 (per 3.1.6) with final hold temperature 265±100F for 190 to 205 minutes.

2.4 Workmanship Requirements

2.4.1 Appearance

The material shall be visually uniform in quality and condition. The material shall be uniformly wetted, with no resin-starved areas, resin-rich areas, particles of uncured resin, or dry and boardy areas (areas where resin has advanced beyond B-stage). It shall be free of dirt and other foreign material. The prepreg material shall not contain crimps, puckers or folded sections in the as-rolled condition.

2.4.2 Unidirectional Tape Workmanship Requirements

2.4.2.1 Gaps.

Gaps between fibers shall be no greater than .032 inches wide and 10 inches long. Gaps caused by breaks in individual tows shall not exceed .12 inches in length. No more than two such gaps are permitted per square foot of material.

2.4.2.2 Splices

Minimum spacing between fiber splices shall be 3 inches.

2.4.2.3 Fiber Straightness

Fibers shall be straight and collimated within .03 inches per linear foot of material.

2.4.2.4 Fiber Balls

Fiber balls, which do not distort fibers, do not cause tow separation, and are pressed flat, are acceptable provided that the maximum accumulated area of fiber balls does not exceed 1.5 in2 in any 1 ft2 of material. Fiber balls must not increase the material thickness more than 10%. Other types of fiber balls are not allowed.

2.4.2.5 Prepreg Pucker.

Puckers (catenary) in the unrolled condition shall be tested per Paragraph 3.2.8.1.

2.4.2.6 Width

Width of the material shall be 12±0.10 inches. The prepreg shall be flush with the edge of the liner.

2.4.3 Tack

Tack shall be tested per paragraph 3.2.9.

2.4.4 Liners

Liners (i.e. backing paper) shall not alter the physical, chemical or mechanical properties of the prepreg. Liners shall be easily removable at ambient temperature. No removal of prepreg resin by the liner is permitted, and only minimal transfer of liner release agent is allowed. The following liner materials are permitted:

a) Manufacturer: Loparex Base paper: 60# clay coat Release: Silicone release Release levels: 18C/20D

b) Manufacturer: Wausau-Mosinee (Rhinelander) Base paper: 78# clay coat (4.7 mil) Release: Silicone release Release levels: A1030/B430

c) Manufacturer: Loparex Base paper: 74#, BL C2S9670/9695

d) Manufacturer: Gascogne Identification: ISD67

Use of any other liner materials must be reviewed and approved by the GSFC Materials Engineering Branch prior to use.

2.4.5 Out Time

Cumulative Out time of the material at room temperature shall be 14 days minimum. The material shall meet all requirements of this specification through the duration of the out time.

2.4.6 Shelf Life

Shelf Life of the material when stored at 0°F and below shall be 6 months from date of manufacture. The material shall meet all requirements of this specification through the duration of the shelf life.

2.5 Nonconforming Material

A roll condition log shall be provided with each roll of material. The roll condition log shall list the type, location and longitudinal length of each defect and shall allow the purchaser to locate defects from the start of the roll to an accuracy of ±3 feet.

Defective areas shall be clearly marked along the edge of the material at the beginning and end of the defective area. Use a single marker for point defects. Mark continuous defect areas every 2 feet. Multiple tow defects closer to each other than 3 feet shall be considered as a continuous defect length.

Defective areas shall not be included in the net purchased weight of the material. The total defective length per roll shall not exceed 15% of the total roll length.

2.6 Material Handling

Proper handling of the prepreg material is essential to prevent excessive outgassing and to ensure adequate material properties. Prevention of exposure of the material to moisture is particularly important.

The prepreg material shall be packaged in a clean, water vapor proof bagging material per MIL- PRF-131 or equivalent. The bagging shall be heat sealed to prevent moisture entrapment.

Desiccant of sufficient size shall be placed inside the bagging with the prepreg material at all times.

A log sheet shall be maintained with each roll of material. The log sheet shall record the date, out time and ambient temperature and humidity for each time the roll is removed from the freezer.

The log sheet shall be retained by the fabricator.

Prepreg shall be used in an environment that meets the requirements of Figure 1. The sealed package shall not be opened at any time, including incoming inspection, before the material has reached room temperature. This is to prevent moisture from condensing on the prepreg material.

The time for a roll to come to room temperature is 8 hours minimum. The outside of the package shall be checked for condensation and shall not be opened if moisture is present on the bagging material.

If the material will not be used within 24 hours after reaching room temperature, the prepreg material shall be repackaged / resealed and returned to the freezer.

Prior to returning the prepreg material to the freezer, excess air shall be removed and the package shall be sealed.

Figure 1. Prepreg Handling and Processing Area Environment

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. The test methods specified herein shall be used unless specifically pre-approved by the purchaser.

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 Sampling

Each lot of material, as defined below, shall be tested with the sampling as defined below. If the purchased quantity exceeds the limits of the supplier for a single fiber lot or resin batch, the specified testing shall be performed on each lot as required.

3.1.1 Prepreg Lot/Batch

A lot shall consist of all rolls of prepreg material produced by one supplier, at one plant and on the same production line, from the same lot of fiber or fabric and the same resin batch.

3.1.2 Fiber Lot

A fiber lot shall consist of fiber produced in a single production run, made from a single batch of raw materials and the same surface treatment. Blending of up to 3 lots of Toray or Cytec certified fiber of the same type and tow size shall be allowed. All fibers shall have the same surface treatment.

3.1.3 Deleted

3.1.4 Resin Batch

A resin batch shall consist of resin mixed at the same time in the same mixer, with traceability to individual chemical lots. Resin bending of up to 15% of other 954-6 resin batches is allowed.

All 954-6 resins shall be chemically similar and shall not compromise the shelf life of the master blend.

3.1.5 Uncured Material Physical Property Test Sampling

Each roll in the lot shall be tested for resin content and fiber areal weight. The first and last rolls in the lot shall also be tested for volatile content, gel time, and resin flow.

3.1.6 Mechanical Property Test Sampling

The sampling plan for mechanical properties is specified in Table 5. Cure I.A.W Hexcel cure cycle HSP-C4 with final hold temperature 265±10F for 190 to 205 minutes. Hexcel can use the following cure cycle for HSP-C4

1.) Place vacuum-bagged lay-up in autoclave and close autoclave 2.) Apply minimum vacuum of 22 inches Hg 3.) Pressurize autoclave to 90-110 psig before temperature ramp, vent bag when pressure reaches 20 psig

4.) Heat part at a rate of 1 to 40F per minute to 255-2750F 5.) Hold part at 255-2750F for 190-205 minutes 6.) Cool part at a rate of 50F per minute maximum to below 1400F 7.) When part cools to below 1400F, pressure may be vented and part removed.

*Note: Vacuum may not reach 22 inches Hg in Hexcel Salt Lake where 20 inches Hg is an attainable reading

Table 5. Mechanical Property Sampling Plan

Number of Rolls in Lot Number of Rolls in Lot to be Sampled 1-5 First 6-15 First and Last 16+ First and Last + every tenth roll

3.2 Physical Property Test Methods

3.2.1 Fiber Areal Weight and Resin Content

Fiber areal weight and resin content shall be tested per ASTM C 613, the method in MIL-T- 29586, paragraph 4.7.1.2, or ASTM D 3529 (ASTM D 3776-96 for fabric). For Hexcel supplied prepreg, the fiber areal weight and resin content shall be tested per HSP-R4, rev. 2.

3.2.2 Fiber Volume Fraction and Void Content

Fiber volume fraction and void content for cured test laminates shall be determined per ASTM D 3171 and ASTM D 2734. A microwave assisted digestion method for removing resin is acceptable.

3.2.3 Volatile Content

Volatile content shall be tested per ASTM D 3530 or approved equivalent.

3.2.4 Resin Flow

Resin Flow shall be tested per ASTM D 3531 or approved equivalent.

3.2.5 Gel Time

Gel time shall be determined per ASTM D 3532 or approved equivalent, such as the Fisher- Johns method in MIL-T-29586, paragraph 4.7.1.3.1.

3.2.6 Glass Transition Temperature

Tg shall be tested in accordance with Hexcel Flex Test Method, HSP-T2 with the exception of ramp rate which shall be 5°C/min

3.2.7 Cured Ply Thickness

The cured ply thickness shall be determined for each mechanical test laminate, as follows: Using a single 0.25-inch diameter-ball-face micrometer capable of reading to .0001 inch, perform a minimum of 10 measurements over the surface of the laminate. Measurements should be taken at least 1.0 inches inboard of an unfinished edge on a laminate. Calculate the ply thickness as the average thickness of the specimen divided by the number of plies.

3.2.8 Prepreg Visual Tests

The prepreg shall be visually inspected to ensure conformance with Paragraph 3.4. Puckers shall be examined per the following paragraph.

3.2.8.1 Evaluation for Puckers.

After one freezer cycle (<10 ̊ F for 8 hours minimum), lay prepreg flat on table with backing paper next to table. Freezer cycle shall be timed and a tag shall be placed on sample with time/date in freezer. Puckered areas (out of plane condition) shall not exceed 0.1 inches width x

0.2 inches length x 0.020 inches high. No more than 20 puckered areas per square foot prepreg allowed after 15 minutes.

An alternative evaluation method may be used subject to GSFC approval.

Puckers exceeding .12 inches in height and exceeding an accumulated area of 2 square inches per square foot of material shall be cause for rejection.

3.2.9 Tack

Tack shall be verified as follows:

Cut two 1 by 3 inch prepreg samples, with fibers parallel to the 1-inch dimension, leaving the liner on. Apply one piece of material (with liner side up) to a clean piece of austenitic corrosion resistant steel with a commercial 2D finish or a 125 RMS finish. Apply light pressure with a roller to flatten the material, and then remove the liner. Apply the second piece of prepreg over the first piece. Apply light pressure with a roller, and then remove the liner. Place the test plate such that the 3-inch dimension of the prepreg is oriented vertically. The material must adhere completely for 30 minutes minimum at a temperature of 75±5°F and >80%relative humidity.

• This test is only required for one spool per lot

3.2.10 Thickness Variability

Thickness of an uncured lamina specimen shall be measured for variability (uniformity) as follows:

Lay-up 2-inch by 3-inch specimens with 11 plies. Orient plies in specimens such that the fiber tows stack top of each other from ply to ply (worst-on-worst thickness variation condition). The two-inch dimension shall be parallel to the fiber direction. The 3-inch dimension shall be perpendicular to the fiber direction and across the tape width.

Vacuum compact each ply for a minimum 5 minutes at 18 inches Hg or more.

Use a height gage (accurate to 0.5 mils or better) with a 1/16-inch-diameter contacting foot to measure the thickness continuously across width of the specimen within a 0.25 inch border from the specimen edges, as the height gage is passed four times across the specimen in even passes.

Record the maximum and minimum thickness measurements. Calculate the difference between the maximum and minimum thickness for comparison with requirement.

Refer to Figure 2 for specimen measurement.

This test is required for one spool per lot.

3.3 Mechanical Property Test Methods

Testing for fiber volume fraction (per 3.2.2) and void volume fraction testing (per 3.2.2) shall be performed on all mechanical test laminates. Thickness and width measurements shall be performed for each mechanical test specimen. Allowable void volume for test laminates shall be less than 2.0%. The cure cycle utilized to cure the test laminates shall be reported as part of the certification data package.

3.3.1 Tensile Testing

Tensile strength and modulus shall be tested per ASTM D 3039. The modulus shall be determined based on a linear fit of strain data between 0.1 percent and 0.2 percent strain.

3.3.2 Compression Testing

Compression strength and modulus shall be tested per ASTM D 695, modified method, or SACMA SRM-1. The modulus shall be determined based on a linear fit of strain data between

0.01 percent and 0.1 percent strain. Hexcel shall use a compression thickness of .08 ± .01 thickness

3.3.3 Short Beam Shear Testing

Short beam shear strength shall be tested per SACMA SRM-8 or ASTM D 2344. The thickness of the test laminate shall be 0.080 ± 0.010 inches.

3.4 Retest

If the lot or roll test results do not comply with the requirements of Section 3, the roll shall be retested using the original number of samples. If the second set of tests does not meet the specified requirements, the roll shall be rejected. If other testing (i.e., mechanical property testing) has been performed on the rejected roll, such testing shall be repeated using samples from an adjacent roll. The second failure to comply shall be cause for rejection of the lot.

3.5 Requalification After Expiration of Shelf Life

This section applies to flight hardware made with prepreg in this specification.

Material that has exceeded the shelf life requirement of Section 3 may be requalified for a maximum of 6 months beyond the original shelf life or for a total life of one year from date of original certification. The testing required to recertify the material shall be the following:

a. Resin flow

b. Resin gel time

c. 00 short beam shear at room temperature

d. Other tests as specified by engineering and quality functions

For all recertification tests, the number of samples and test conditions shall be the same as the original certification tests.

Figure 2. Prepreg Variability Measurement

¼” Typical 2 Places

¼” Typical 2 Places

Measurement Region

Fiber Direction

2”

3”

Measurement Pass Number

4 PREPARATION 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 certificate shall show the lot and batch numbers and the date of manufacture for material traceability.

The supplier shall submit two copies of 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.

4.2 Packaging

All material shall be packaged in such a manner as to prevent damage during shipment.

The material shall be supplied on non-contaminating rolls, which support the material and prevent direct contact with the material. Each roll shall be supported within its shipping container such that it will not be damaged by its own weight, by the weight of dry ice, temperature recorders, or any other material inside the container during shipment or storage. A sealed inner bag of non-contaminating material shall be used inside the outer bag for shipment.

The roll shall be packaged with sufficient dry ice to ensure that the material will remain below 0°C until receipt by the purchaser.

The maximum weight of unidirectional material on each roll shall be 35 pounds. The maximum weight of fabric material shall be 35 pounds or 50 linear yards. Minimum continuous length of prepreg allowed in any roll is 50 feet.

The supplier shall not ship the prepreg over weekends or holidays without permission of the purchaser.

4.3 Temperature Monitoring

Two (2) temperature recorders are required per shipment.

4.4 Material Identification Labeling

Each roll of material shall be labeled with the following information:

a) Manufacturer's name and address

b) Manufacturer's designation

c) Purchase Order Number

d) Spec number per this specification

e) Material width, nominal material thickness

f) Length of material on roll

g) Fiber type

h) Lot / Batch number

i) Date of impregnation

j) Roll number

k) "CAUTION: Temperature Sensitive Material Store Below 0°F (-18°C)"

5 NOTES

5.1 Intended Use

These materials are intended for use in the fabrication of spacecraft structures where high strength/weight and stiffness as well as low outgassing are required, and resin will not be bled out of the material during cure.

5.2 Ordering Data

Purchase orders for this material should include the following:

a) Title, number and date of this specification

b) Spec number required

c) Quantity required

5.3 Sources of Supply

Hexcel Composites, Inc.

P.O. Box 18748 Salt Lake City, Utah, 84118-0748 Telephone: (801) 508-8371 Fax: (801) 503-8103

Appendix A Abbreviations and Acronyms

Abbreviation/ Acronym

DEFINITION

GSFC Goddard Space Flight Center TBD To Be Determined TBR To Be Revised TBS To Be Scheduled SPEC Specification IC Instrument Carrier CCB Configuration Change Board PSI Pounds per square inch PSIG Pounds per square inch gauge Hg Mercury ASTM American Society for Testing Materials RMS Root mean square SACMA-SRM Suppliers of Advanced Composite Materials Association-SACMA recommended method

1.4 Document Precedence