U.
S. Department of Transportation Federal Aviation Administration Advisory Circular Subject: Repairs and Alterations to Composite and Bonded Aircraft Structure Date: 7/23/16 AC No: 43-214A Initiated by: AFS-300 Change:
1 PURPOSE. This advisory circular (AC) provides information and guidance concerning an acceptable means, but not the only means, of demonstrating compliance with the requirements of Title 14 of the Code of Federal Regulations (14 CFR) parts 21, 23, 25, 26, 27, 29, 31, 33, 35, 43, 91, 121, 125, 129 (U.S.-registered airplanes), 133, 135, 137, and 145 regarding procedures and facilities for repairs and alterations of structures consisting of adhesively-bonded (including metal bond) and fiber-reinforced materials
(e.g., carbon, aramid, and glass-reinforced polymeric materials mentioned in the current edition of AC 20-107, Composite Aircraft Structure). The information in this AC is applicable to repairs and alterations of bonded and composite structures, whether it is a damaged part that can be removed from the airplane for repairs, or repairs and alterations on the aircraft itself. Examples include repair patches, on-wing bonded repairs, and fabrication and bonding of replacement parts. The Federal Aviation Administration (FAA) will consider any other method of compliance that the applicant elects to present.
This AC uses mandatory terms such as “must” only in the sense of ensuring the applicability of these particular methods of compliance when using the acceptable means of compliance (AMC) described herein. This AC does not change regulatory requirements and does not authorize changes in, or deviations from, regulatory requirements.
2 DEFINITIONS.
1. Batch. In general, a quantity of material formed during the same process or in one continuous process and having identical characteristics throughout, using a discrete quantity of material with commonality of raw materials and process history.
2. B-Stage. An intermediate stage in the reaction of certain thermosetting resins, in which the material (plastic and fusible) softens when heated, but may not entirely dissolve or fuse. This stage helps facilitate handling and processing.
The resin in an uncured, pre-impregnated (prepreg) material is usually in this stage.
3. Composite. A combination of two or more materials (reinforcing elements, fillers, and composite matrix binder), differing in form or composition on a macroscale. The constituents retain their identities, that is, they do not dissolve or otherwise merge completely into one another, although they act in
2 concert. Normally, the components can be physically identified and exhibit an interface between one another.
4. Critical Structure. A load-bearing structure/element whose integrity is essential in maintaining the overall flight safety of the aircraft. This definition was adopted because there are differences in the definitions of primary structure, secondary structure, and Principal Structural Elements (PSE) when considering the different categories of aircraft. For example, for transport category airplanes, the critical structures are defined as PSE, and must be defined by the design approval holder (DAH).
5. Debulk. Compacting of an uncured laminate under vacuum and/or moderate heat and pressure (i.e., non-curing conditions) to remove air, to ensure seating on the tool, and to prevent wrinkles.
6. Design Approval Holder (DAH). A person who has been issued a type design approval by the FAA and who controls the design and quality of the product or article. Approval may take the form of a type certificate (TC), Supplemental Type Certificate (STC), Parts Manufacturer Approval (PMA), or Technical Standard Order Authorization (TSOA).
7. Maintenance Organization (MO). Persons performing a repair or alteration under parts 121 and 135, or repair stations certificated under part 145. As used in this AC, this term includes Maintenance Repair Organizations (MRO), certificated repair stations (CRS), and operators’ maintenance facilities.
8. Out Life. The cumulative length of time a material may be out of freezer storage, prior to curing, and still maintain the required processability characteristics and mechanical properties. Also known as a limit on the amount of accumulated out time before further action needs to be taken to ensure the raw material is still usable (also known as work life).
9. Out Time. The cumulative length of time a material spends out of freezer storage.
10. Production Approval Holder (PAH). A person who has been issued a production approval by the FAA, and who controls the manufacturing and quality of the product or article. Approval may take the form of a Production Certificate (PC), PMA, or TSOA.
11. Production Approval Holder (PAH)-Approved Supplier. A supplier that has been approved for direct shipment under a PAH’s PC or foreign equivalent, also known as an approved vendor. The PAH maintains a list of approved suppliers, which may be called the Approved Supplier List (ASL) or the Approved Vendor List (AVL). The PAH is responsible for ongoing oversight of its approved suppliers in support of its PC.
12. Qualified Material. A raw material that has been qualified in accordance with the requirements of a particular material specification. In general, each specification has an associated Qualified Products List (QPL) that identifies the raw materials that have been qualified to that specification. Qualification of a material to a particular specification does not necessarily mean it is
3 approved for use, unless that specification is called out on a drawing or other document.
13. Shelf Life. The length of time a raw material may be in storage under specific conditions and still meet the requirements of the applicable material specification, also known as storage life.
14. Shipment. An order of raw material received by a purchaser. A shipment of prepreg may include rolls of raw material from more than one batch and more than one lot. A shipment of resins or adhesives may include resins or adhesives from one or more batches and more than one lot.
3 RELATED READING MATERIAL (current editions).
3.1 FAA ACs:
• AC 00-56, Voluntary Industry Distributor Accreditation Program.
• AC 20-107, Composite Aircraft Structure.
• AC 21-26, Quality System for the Manufacture of Composite Structures.
• AC 21-47, Submittal of Data to an ACO, a DER or an ODA for a Major Repair or a Major Alteration.
• AC 23-20, Acceptance Guidance on Material Procurement and Process Specifications for Polymer Matrix Composite Systems.
• AC 43.13-1, Acceptable Methods, Techniques, and Practices—Aircraft Inspection and Repair.
• AC 43.13-2, Acceptable Methods, Techniques, and Practices—Aircraft Alterations.
• AC 43-210, Standardized Procedures for Requesting Field Approval of Data, Major Alterations, and Repairs.
• AC 65-31, Training, Qualification, and Certification of Nondestructive Inspection Personnel.
• AC 65-33, Development of Training/Qualification Programs for Composite Maintenance Technicians.
• AC 120-77, Maintenance and Alteration Data.
3.2 SAE Documents:
3.2.1 Procedures.
• SAE ARP4916, Masking and Cleaning of Epoxy and Polyester Matrix Thermosetting Composite Materials.
• SAE ARP4977, Drying of Thermosetting Composite Materials.
• SAE ARP4991, Core Restoration of Thermosetting Composite Components.
• SAE ARP5089, Composite Repair Ndt/Ndi Handbook.
• SAE ARP5143, Vacuum Bagging of Thermosetting Composite Repairs.
• SAE ARP5144, Heat Application for Thermosetting Resin Curing.
• SAE ARP5256, Mixing Resins, Adhesives and Potting Compounds.
• SAE ARP5319, Impregnation of Dry Fabric and Ply Lay-Up.
• SAE AIR5431, Repair Tooling.
3.2.2 Training.
• SAE AIR4938, Composite and Bonded Structure Technician/Specialist: Training Document.
• SAE AIR5278, Composite and Bonded Structure Engineers: Training Document.
• SAE AIR5279, Composite and Bonded Structure Inspector: Training Document.
• SAE AIR5719, Teaching Points for an Awareness Class on “Critical Issues in Composite Maintenance and Repair.”
3.2.3 Nondestructive Inspection (NDI) Standards.
• SAE ARP5605, Solid Composite Laminate Ndi Reference Standards.
• SAE ARP5606, Composite Honeycomb Ndi Reference Standards.
3.2.4 Other. SAE AIR5416, Maintenance Life Cycle Cost Model.
3.3 FAA Orders and Policy Statements:
• FAA Order 8300.16, Major Repair and Alteration Data Approval.
• FAA Order 8900.1, Flight Standards Information Management System (FSIMS) Volume 3, Chapter 67, Section 1, Evaluating the Size Limits for Bonded Repairs.
• PS-ACE100-2001-006, Static Strength Substantiation of Composite Airplane Structure, dated 12/21/2001.
• PS-ACE100-2002-006, Material Qualification and Equivalency for Polymer Matrix Composite Material Systems, dated 9/15/2003.
• PS-ACE100-2004-10030, Substantiation of Secondary Composite Structures, dated 4/19/2005.
• PS-AIR-20-130-01, Bonded Repair Size Limits, dated 11/24/14.
3.4 Other Documents:
• ASTM D3878, Standard Terminology for Composite Materials.
• Composite Materials Handbook-17 (CMH-17).
• Major Repair and Alteration Data Approval (Job Aid).
• SAE AIR4844, Composites and Metal Bonding Glossary.
4 BACKGROUND. This AC provides information on repairs and alterations to composite and bonded aircraft structure, and on facilities, equipment, and inspection processes that an MO with the appropriate ratings must have to perform repairs and alterations on such structures. These guidelines supplement the procedures in the DAH’s Structural Repair Manuals (SRM). In addition, the MO must perform all major repairs and alterations using data approved by the FAA Administrator. The word “composites,” as used in this AC, does not imply a relationship with a CRS Airframe Class 1 or Class 2 composite construction rating. Also, operations under parts 91, 121, 125, 129 (U.S.-registered airplanes), 133, 135, and 137, and repair stations certificated under part 145, must comply with part 43, § 43.13.
5 ENGINEERING DATA AND PROCEDURES.
5.1 Source of Data.
5.1.1 MO Responsibilities. The MO must accomplish repairs or alterations to composite and bonded aircraft structure in accordance with part 43; part 121, § 121.379; part 129, §§ 129.14 and 129.107; part 135, § 135.437; and part 145. It is incumbent upon the MO to work closely with the DAH of the particular product and the FAA, when necessary, to determine what specific data may be necessary to support the repair or alteration. The DAH’s maintenance manual and SRM contain much of the information needed for maintenance, repairs, and alterations.
5.1.2 FAA Approval. Data for major repairs and alterations must be approved by the FAA (or its designee). FAA approval is also required for major changes to technical data that were previously FAA approved. Minor repairs and alterations, and minor changes to previously approved data, do not require FAA approval. Certain documents associated with the instructions for continued airworthiness (ICA), such as the Aircraft Maintenance Manual (AMM), are acceptable to the Administrator. However, the Airworthiness Limitations section of the ICA is FAA approved. For part 25 airplanes, the SRM and Service Bulletins (SB) are typically approved by the FAA. Where this AC mentions “approved or acceptable data,” refer to AC 120-77 for guidance on which term applies.
5.1.3 Approved Data. The MO must use data approved by the FAA when performing major repairs or alterations. In the event that the DAH’s repair or alteration data are deficient with regard to specific information, techniques, or repair or alteration methods, or if the damage repaired or altered exceeds that covered by the DAH’s repair or alteration data, the MO must obtain FAA-approved data for the major repair or alteration. A simple concurrence by the DAH does not constitute FAA approval. In addition, FAA approval of data is limited to the repair or alteration specified in that data. While an MO can use previously approved data to develop data, the FAA must approve data for a major repair or alteration. Refer to ACs 21-47, 43-210, and 120-77 for additional information.
5.2 Data Requirements and Compliance. Each MO must have and maintain data required to define the materials, configuration, and accomplishment procedures for the repairs or alterations it performs. Data must include the drawings and specifications that define the repair or alteration, including required dimensions, materials, and processes necessary to achieve structural strength and other design properties (e.g., transmissivity, lightning strike protection, and flammability). The data must be approved by or acceptable to the FAA, as appropriate (refer to AC 120-77). MOs must perform and document the inspections and tests required to determine compliance with applicable airworthiness requirements and the approved repair or alteration data.
5.3 Data for Repairs or Alterations Not in Compliance with the DAH’s Manuals. For repairs or alterations other than those defined in the DAH manuals (e.g., AMM or SRM), the following data containing the information indicated must be available and used by the MOs when purchasing and receiving materials, fabricating repairs or alterations, and installing the repairs or alterations. Proprietary information for the substantiation might not be in the MO’s possession, but is retained by the DAH.
5.3.1 Drawings. Engineering drawings must define the following:
1. Materials. A part whose failure could adversely affect safety must be fabricated from (and repaired or altered by) materials that meet approved specifications that ensure that they have the strength and other properties assumed in the design data. Other materials used in the process of repair or alteration (e.g., vacuum bag and breather cloth) may be called out by material manufacturer’s designation;
2. A method and/or illustration of the number of plies and proper stacking orientation/sequence (for composites);
3. Fabrication and processing procedures (may be called out by fabrication and in-production process specification);
4. Shape;
5. Dimensions and tolerances;
6. Location and attachment to existing structure; and
7. Protective coating and sealant.
5.3.2 Substantiation Documentation. FAA-approved or accepted data, as required,
(e.g., engineering reports, analyses, and other data) must show that the repaired or altered structure complies with applicable type certification and airworthiness regulations.
Repairs or alterations to fatigue critical baseline structure (FCBS) and fatigue critical alteration structure (FCAS) must also be evaluated for part 26 requirements, when applicable. The DAH may retain proprietary information and provide the MO with an approval statement (e.g., FAA Form 8100-9, Statement of Compliance with Airworthiness Standards, and/or FAA Form 8110-3, Statement of Compliance with Airworthiness Standards).
5.3.3 Material Specifications. When material specifications are called out in the repair or alteration drawings or other documents, the materials used must meet the qualification requirements in the material specifications. AC 23-20 provides guidance on specifications for polymer matrix composites. Material specifications (for adhesives, resins, prepreg tape and fabric, core materials, metals, etc.) must define the required material and must include the following sections and data:
1. Material Classifications. Identifies the material specified and acceptable types, classes, grades, and styles of that material.
2. Material Properties. Specifies the required physical, processability, chemical, and mechanical (e.g., laminate, sandwich, and bond strength) properties for a material that meets the specification.
3. Material Qualification. Specifies tests and procedures to qualify a material to the specification.
4. Supplier Quality Control (QC). Specifies supplier QC tests and procedures, and specifies compliance certifications and data that the supplier must provide with each material batch.
5. Purchaser QC. Specifies purchaser acceptance test and procedures required for each batch per shipment received.
6. Material Test Methods. Specifies the types of tests, types of specimens, and test procedures for testing the materials for physical, processability, chemical, and mechanical properties.
7. Packaging and Marking Requirements. Specifies requirements for suppliers to follow when packaging and shipping an order of material to a purchaser.
8. Storage Conditions. Specifies environmental conditions and time scale for storage.
9. Recertification Procedures. Specifies the requirements for retest prior to use of over-aged material (i.e., material that has exceeded its out life or shelf life).
10. QPL. Specifies a list of supplier products that are currently qualified to the requirements of the specification. Qualified materials must be listed on an approved QPL and purchased from qualified suppliers. Materials used must be in accordance with the material specifications and their QPL, unless the substitution is in accordance with procedures approved by or acceptable to the Administrator, as appropriate, for the MO.
5.3.4 Fabrication and Process Specifications. Fabrication and process specifications must:
1. Define fabrication and process procedures requirements;
2. List each major step in the fabrication process and process procedure, including in-process tests and inspections. Steps may include a specific repair or alteration sequence (e.g., for repair or alteration on a vertical surface), and specific material mixing requirements;
3. Specify appropriate process verification. If witness test coupons are required, specify type and number of coupons, test method, and acceptable property limits;
4. Define requirements for facility, environmental conditions, equipment, and storage;
5. Specify cure cycle requirements; and
6. Specify qualifications required for the personnel who will carry out the requirements of the specification. This may include qualifications in material control, material handling, and processing techniques, such as mixing, layup, etc. (See paragraph 11.)
5.3.5 NDI Procedures. NDI procedures must:
1. Identify method (ultrasonics, x ray, thermography, etc.);
2. Define NDI methods and outline test procedures;
3. Specify equipment and calibration procedures;
4. Include accept/reject NDI criteria; and
5. Specify the qualifications for the personnel who will carry out the requirements of the specification (see paragraph 11).
5.3.6 Defect Accept/Reject Criteria. The MO must use accept/reject criteria for a cured or bonded structure corresponding to defects considered in the design data. The DAH’s SRM or applicable fabrication specification must identify these criteria. Inspection procedures and equipment used to detect flaws must be consistent with the DAH’s standards or other FAA-approved or accepted data, as applicable (refer to AC 120-77).
6 RAW MATERIAL INSPECTION PROCEDURES.
6.1 General. The processability and resulting strength-related properties of composite materials used in structural repairs or alterations depend upon the composition of the materials from which they are manufactured. In general, a prepreg consists of surface-treated glass, aramid, or carbon fibers impregnated with a reactive and chemically complex resin. Thermosetting resins (e.g., epoxies) are often “staged” or partially reacted during the prepregging process and may undergo compositional changes during transport, handling, and storage.
6.1.1 Resin Changes. Changes in resin composition or improper storage and handling may cause problems in processing. It may have adverse effects on the performance and long-term properties of many composite repairs or alterations. This also applies to adhesive systems used in structural bonding (e.g., film adhesives and primers).
6.1.2 Material Tests. The capability of a repair or alteration to satisfactorily maintain its structural integrity for the remaining life of the part or aircraft is dependent, in part, on the MO’s knowledge of the physical, processability, chemical, and mechanical properties
9 of the incoming raw materials used (e.g., prepreg materials and adhesives). The physical, processability, chemical, and mechanical test results are, therefore, vital to the continued airworthiness of the structure.
6.2 Material Acceptance.
6.2.1 General. The MO must have a material receiving plan that addresses incoming material control and conditions to ensure the incoming material is stored properly prior to material acceptance, and a plan addressing the issues in paragraph 6.1.2 that ensures conformity of purchased material to appropriate material specifications. The MO is responsible for ensuring that the materials are protected from contamination, temperature deviations, and problems caused by storage and handling after the original manufacturing process after receipt of the material (see paragraph 7 for material handling and storage procedures).
6.2.2 Materials Without Reference to Specification. Nonstructural materials that have no impact on the strength of the repair or alteration may be used without a controlling material specification. These materials are typically consumable items, such as bagging film, breather cloth, etc. Materials called out in the SRM, maintenance manuals, or other repair or alteration documents without reference to a material specification and without requirements for storage, handling, and processing, must be controlled as indicated in the material manufacturer’s recommendations covering designation, storage, and handling requirements.
6.2.3 Supplier QC Testing. The materials supplier is responsible for supplier QC testing (also known as batch acceptance testing) on each batch of material, as defined in the applicable material specification (see paragraph 5.3.3). Copies of the original material manufacturer and supplier laboratory test reports showing actual test results, if applicable, must accompany each batch of material received for purchaser review and approval.
6.2.4 Purchaser QC Testing and Receiving Inspection. The MO is responsible to ensure purchaser QC testing and receiving inspection are accomplished on each batch of material received, as defined in the applicable material specification (see paragraph 5.3.3). As part of its incoming material acceptance plan, the MO may choose to perform the purchaser QC testing itself, to have the testing performed at an independent laboratory, or to rely on the purchaser QC testing accomplished by a material vendor or distributor. Once the MO establishes confidence in the quality of materials received from a particular source, it may reduce the level of testing, in accordance with a QC plan approved by the Administrator.
6.2.5 Purchasing Material from a PAH-Approved Supplier. The SRM, material specifications, or related documents may include a list of PAH-approved suppliers/vendors for the materials used in the repairs or alterations, and may state that materials purchased from these PAH-approved suppliers qualify for an exception to the requirements for purchaser testing in the applicable material specification.
6.2.5.1 In this case, the MO may waive the purchaser control testing required by the material specifications for materials purchased from a PAH-approved supplier.
6.2.5.2 The PAH assumes responsibility for the exception to the specification requirements, and performs quality audits to assure that the supplier manufactures and controls the material in accordance with accepted industry standards and the applicable specification requirements.
6.2.6 Purchasing Material from a Distributor. If the PAH or foreign equivalent identifies the distributor as a PAH-approved supplier, then the MO may rely upon the systems in place to address material handling and storage issues. If the distributor is not identified as a PAH-approved supplier, then the MO must provide oversight. Refer to AC 00-56 for acceptable procedures for such oversight. Distributors must provide the purchaser with a copy of the supplier’s initial paperwork for traceability. Since distributors typically buy large quantities of material and subdivide it, an MO should consider the following issues:
1. Possible contamination by water condensation or chemicals, such as mold release compounds and oils (see paragraph 7 for material handling and storage procedures).
2. Additional out time accumulated during cutting.
3. Procedures for protecting the raw material during shipment and after cutting.
In some cases, the material specifications and SRMs do not envision the use of distributors, so the MO must address what is required through other means.
4. Recording of storage time and environmental exposure (e.g., temperature and humidity). The MO must have a system that ensures that knowledge of storage and shipment times and environmental exposures are known, and in compliance with the requirements, through whatever path is taken from the material manufacturer until the material is in environmentally-controlled storage at the MO. Temperature recorders used from the material supplier to the distributor will usually have expired by the time the raw material is shipped to the MO. This means that the distributor must supply temperature recorders in the shipment from the distributor to the MO.
6.2.7 Types of Tests. The following paragraphs identify QC tests of physical, processability, chemical, and mechanical properties that an MO will ensure are performed, as specified in the material QC sections of the applicable FAA-approved material specifications.
6.2.7.1 Physical Tests. Physical tests typically include resin content and fiber area weight, volatile content, tack, flow, and gel time.
6.2.7.2 Processability Tests. Laminate processability tests may include laminate ply thickness measurements, resin content, void content, and density tests conducted on laminates fabricated from at least one roll per batch of prepreg material.
6.2.7.3 Chemical Characterization Tests. High performance liquid chromatography (HPLC) and Infrared Spectroscopy (IR) are two chemical characterization tests that provide the capability for rapid screening and QC fingerprinting of the resin’s constituents. They are applicable both to prepregs and adhesive resins. HPLC and IR are fundamentally different test methods. They provide direct, but different, information about a resin’s composition. The supplier conducts HPLC and IR tests to ensure that the resin type, purity, concentration, and the distribution of resin components are consistent from batch to batch and per the material specification. In the case of prepreg, the supplier conducts these tests on resin samples extracted from a number of rolls in each batch of prepreg material. B-staging alters the chemical composition of the resin, increasing the variety of chemical components. The resin may chemically advance as a function of time in the prepreg.
6.2.7.4 Mechanical Tests. Mechanical testing should be relevant to the intended use of the material. The use of standard test methods is recommended. For adhesive bonding, appropriate tests include lap shear, wedge, climbing drum, T-peel, and fracture toughness (GIc) tests. For laminates, the mechanical property tests normally include longitudinal tension (room temperature, ambient), compression (room temperature and elevated temperature, both ambient), short beam shear (room temperature, ambient), and double cantilever beam (DCB) (room temperature, ambient). The room temperature ambient tensile modulus of elasticity and ultimate tensile strain are obtained from the stress-strain curve of the longitudinal tension test. For sandwich structures, the mechanical property tests normally include at least flatwise tensile and four-point bending tests.
7 MATERIAL HANDLING AND STORAGE PROCEDURES.
7.1 General. Improper refrigerated storage and handling of materials, such as prepreg tape, core, core splice, fabric, adhesives, potting compounds, and resins can adversely affect the structural integrity of the finished part. Therefore, an MO’s accepted system for bonding of aircraft structure and for composite material repair and alteration must include specified procedures for storage and handling of raw materials. The MO’s accepted procedures must require materials to be stored and handled in ways that ensure they will be acceptable for use and will provide expected finished properties when processed.
When stored at specified temperatures, material specifications normally specify material shelf life. The MO must carefully follow instructions regarding handling and storage.
7.2 Shelf Life and Temperature Considerations. The MO must handle and store polymer matrix prepreg tape and fabric, adhesives, potting compounds, and resins in accordance with the requirements of the appropriate FAA-approved material specification to ensure retention of material properties. Thermoset matrix composites and structural adhesives are typically stored in sealed containers or bags at 0 ºF (-18 ºC) to retard the “aging,” or partial curing, of the polymer and to extend the shelf life. The sealed containers or bags prevent moisture absorption and moisture condensation on the cold material. When the MO removes the material from the freezer for processing, it thaws within the sealed
12 container or bag until the condensation on the exterior has dissipated. Thin rolls of prepreg and adhesives do not need as long a thaw period. The MO must document the allowed accumulated period of time and track the actual accumulated time the material is outside the freezer. The MO’s FAA-accepted system must include recordkeeping procedures for shelf life and out time.
7.3 Storage and Handling. Polymer matrix prepreg materials and film adhesives normally have a backing sheet that improves their handling characteristics and protects the raw material from handling-related damage. Nonwoven, unidirectional tapes, for example, can otherwise easily split between fibers.
7.3.1 Support of Material. Materials must be supported by the ends of the support tube, or in their original shipping container, to prevent flat spots on the materials. Stacking of rolls on top of one another is not allowed.
7.3.2 Contamination Prevention. Clean hands are mandatory when working with these raw materials. Appropriate gloves are required when handling adhesives, prepregs, and surfaces prepared for bonding or layup, as called out in the process specification. Gloves prevent contamination of the bonding surface or prepreg and protect the personnel, since many people are sensitive to adhesives and resins.
7.3.3 Damage Prevention. The MO personnel can damage many of today’s composite material fibers if they bend or fold them with small radii. For this reason, handling procedures should prohibit sharp bending, creasing, gouging, or other actions that could break or damage fibers. Properly trained personnel must handle these materials.
7.3.4 Storage Procedures. The MO’s procedures for storage and handling of these raw materials must include the following:
1. Using frost-free cold storage equipment. A freezer that opens from the top is recommended. An MO may use walk-in freezers for large volume storage.
2. Using a temperature gauge or thermometer. The temperature gauge or thermometer should be calibrated as per manufacturing specifications.
3. Identifying which raw materials (e.g., prepreg tapes and fabrics, film adhesives, and paste adhesives) an MO must store in a freezer.
4. Placing a tag or record on each roll or container showing the batch number, lot number, roll number, shelf life ending date, and the total, allowable, and accumulated out life. The tag or record must include a place to record accumulative out life.
5. Specifying the highest allowable freezer storage temperature.
6. Regularly monitoring freezer storage temperature.
7. Requiring that the MO stores raw materials in moisture-tight bags or containers in the freezer to prevent moisture absorption. If an MO returns kitted parts to the freezer for storage, the MO should also place them in