this NASA Technical Standard include outgassing characteristics, dielectric properties, 
surface/volume electrical resistivity, and flammability. 


 Common Aspects Required of AM Polymer Material Characterization 

6.11.5.1.1 Importance of Anisotropy Characterization 

Due to limitations in the ability to affect microstructural evolution in polymeric AM materials, 
evaluation of the effects of anisotropy on mechanical properties may require more detailed 
evaluation than for metallic materials with fully recrystallized microstructures (see section 6.7.3 in 
this NASA Technical Standard.)  

6.11.5.1.2 Viscoelastic and Viscoplastic Response in Mechanical Properties 

[AMR-83]  For Class B parts, loading rate dependence of mechanical properties, commensurate 
with application environments, shall be accounted for during material characterization and 
derivation of material allowables and design values. 

[Rationale:  Mechanical response of polymeric materials may demonstrate significant load rate 
dependence. Understanding application loading rates and testing the material accordingly is 
required for accurate material characterization.]  

Awareness of strain rate in testing plastic materials is required by the common test standards (e.g., 
ASTM D638). These test methods typically target a standardized testing rate that leads to specimen 
failure in 0.5 to 5 minutes. If the service environment includes higher strain rates, then this 
requirement intends that material properties also be evaluated at a strain rate equal to or greater 
than that of the service environment. 

6.11.5.1.3 Notch Sensitivity 

[AMR-84]  For Class B parts, materials with plastic tensile strain capability less than 3% shall be 
evaluated for notch sensitivity, commensurate with the applicable design criteria and structural 
assessment methods. 

[Rationale:  The effects of stress concentrations on materials with limited ductility may be 
unpredictable for brittle anisotropic AM materials with potentially unique failure mechanisms. 
Testing is required to confirm assessment failure criteria assumptions.] 

Materials with limited ductility, defined here as materials with less than 3% tensile elongation 
(plastic strain), should be assessed using a “brittle material” design criteria (e.g., evaluation of the 
peak maximum principal stress at the surface of the stress concentration). Consult structural 
assessment requirements for policy. 

Test configurations for notches and test methods are not dictated by this NASA Technical Standard. 
A range of stress concentration values oriented to act on the plane of least ductility is recommended 
for evaluation. 


6.11.5.1.4 Determination or Knowledge of Tg for Design 

[AMR-85]  Class B parts shall not be used in environments with an operational range that causes 
the part to pass through its glass transition temperature (Tg), measured in accordance with ASTM 
D7028, Standard Test Method for Glass Transition Temperature (DMA Tg) of Polymer Matrix 
Composites by Dynamic Mechanical Analysis (DMA), or equivalent, unless otherwise substantiated 
as part of the integrated structural integrity rationale in the PPP (see section 7.3 of this NASA 
Technical Standard).  

[Rationale:  Polymeric material response may differ greatly at temperatures above and below the 
Tg; part applications are designed to remain either above or below the Tg to avoid the risk of highly 
variable material response.] 

The “acceptable” tolerance varies with respect to the crystallinity of the respective polymer. For 
amorphous thermoplastics, a material-dependent margin exists around Tg prior to reaching altered 
mechanical response due to increased polymeric chain mobility at elevated temperatures. 
Additionally, as Tg is an intrinsic property with respect to a material's chemical composition, more 
than one Tg may exist for a given material under different crystallinity phases. Crystalline and semi-
crystalline thermoplastics additionally exhibit their crystallization (Tc) and melt temperature (Tm) as 
an indicator of transitioning through the amorphous phase into the crystalline phase. Note:  The 
physical properties of thermoplastics can vary significantly as they transition through these stages.  

The heat deflection temperature (HDT) is commonly mistaken as an interchangeable property with 
Tg. The HDT is an independent characteristic of a material's deflection at increased temperature 
and is not applicable for characterizing the Tg of a polymer. Measuring the HDT of a thermoplastic, 
however, can provide useful information for understanding material stiffness at elevated 
temperatures and is recommended for parts under applicable load cases. 

A common method for measuring the HDT of a polymer is through ASTM D648, Standard Test 
Method for Deflection Temperature of Plastics Under Flexural Load in the Edgewise Position. 

6.11.5.1.5 Conditioning of Specimens for Moisture Content 

[AMR-86]  For Class B parts, the moisture content of all polymeric test materials shall be known 
and controlled during property characterization to within a user-defined predetermined range. 

[Rationale:  Moisture content can have significant influence on the performance of many polymeric 
materials.] 

The interaction of moisture content and temperature is known to influence polymer material 
behavior; application temperature (or bounding values of temperature) should be included in the 
evaluation.  


6.11.5.1.6 Use of Filled or Reinforced Polymer Materials 

[AMR-87]  For Class B parts, structural reinforcement added to AM polymer materials shall be of 
nominally random orientation.  

[Rationale:  Directional or continuous structural fiber reinforcement is currently not allowed in the 
scope of the NASA Technical Standard for AM parts due to the risk in process and 
characterization.] 

Non-structural directional reinforcement used for other purposes is permitted (e.g., thermal 
conductivity, dielectric performance, electrical traces, etc.). 

 Mandatory Environmental Influence Factors for Design Values 

There are environmental factors that are considered essential to the development and application of 
reliable design values in polymeric materials.  

6.11.5.2.1 Temperature and Environmental Effects 

[AMR-88]  For Class B parts, as required for part assessment, the MPS shall include the effect of 
temperature, moisture, and other environmental effects on material properties based on testing of the 
AM product form. 

[Rationale:  Temperature and environmental effects can vary with material product form; 
characterization of these effects on properties is required in the AM product form.]  

6.11.5.2.2 Chemical Compatibility 

[AMR-89]  For Class B parts, compatibility of the polymeric AM material with any chemicals with 
a known potential for exposure to the AM material during manufacture or in service shall be 
evaluated for any detrimental influence on material performance. 

[Rationale:  Polymer material response varies greatly when exposed to a variety of chemicals 
present in spacecraft systems and associated manufacturing processes, leading to the potential to 
significantly reduced material performance.] 

These chemical compatibility tests are intended to take place on AM materials produced to a QMP 
representative of that used for the parts. 


 Physical and Constitutive Properties 

[AMR-90]  For Class B parts, all physical and constitutive properties required for proper design 
assessment shall be evaluated on representative AM polymeric materials. 

[Rationale:  Physical and constitutive properties of materials can be a function of the AM process 
generating the final product form; evaluation of AM materials is required.] 

Physical and constitutive properties are commonly presented as typical basis (mean value) and can 
be defined as a function of environmental conditions (e.g., temperature, humidity, pressure, etc.). 
Note that the relevance of specific properties varies with respect to polymeric process and 
application. Useful guidance for the test and evaluation of these properties can be found in CMH-
17. 

Examples of physical and constitutive properties include Tg, thermal conductivity, elastic moduli, 
Poisson’s ratio, and heat deflection temperature. 

 Material Allowables for Tension and Compression Properties 

[AMR-91]  For Class B parts, derivation of static strength material allowables in tension and 
compression shall be governed by the following:  

a. Test specimens are machined to represent bulk AM material and are tested according to 
appropriate polymer material test standards. 

b. Material allowables are bounded by the 99% probability at 95% confidence one-sided 
tolerance limit estimated for the population, using a properly fit statistical distribution. 

c. A minimum of 100 specimens, distributed according to the lot requirements in section 
6.5 of this NASA Technical Standard, are required to initially establish material allowables. 

d. Material allowables incorporate the minimum CoV requirements of section 6.11.3 of this 
NASA Technical Standard. 

e. The property database is maintained by the CEO and updated on a periodic basis as 
additional data become available from process control-related activities, including witness sampling, 
preproduction article evaluations, QMP development, and machine qualification. 

f. Test and data analysis methodologies, except as noted in this requirement, follow the 
intent of the CMH-17 guidelines for static tensile property development. 

[Rationale:  These criteria partially adapt a combination of CMH-17 and MMPDS requirements for 
design values to meet the unique, process-sensitive scenario of AM polymeric materials.]  


An assumption of symmetry in tensile and compressive response for strength and moduli may be 
inappropriate for many of the polymeric AM materials; each of these properties is evaluated 
explicitly. 

When established design values decrease, the programmatic costs are significant. It is strongly 
recommended that initial design values incorporate a design value margin sufficient to guard 
against such a decrease as the supporting data population of the MPS grows and periodic 
reassessments of design values occur. As AM processes and the MPS data population reaches 
maturity, the design values may be allowed to increase by reducing the design value margin if the 
data support. 

The intent of the static strength property requirements of NASA-STD-6016 are satisfied when all 
material characterizations and process controls of this NASA Technical Standard are fully 
implemented. The submittal of an MUA describing the substantiation of the MPS satisfies the NASA-
STD-6016 material property control requirements. This MPS documentation also satisfies material 
property requirements levied by other structural requirements documents (e.g., NASA-STD-5012 or 
JSC 65828). 

 Shear Properties 

[AMR-92]  For Class B parts, material allowables for shear strength shall be explicitly 
characterized, as required for structural assessment, according to the following: 

a. Test specimens are machined to represent bulk AM material and are tested according to 
appropriate polymer material test standards. 

b. Material allowables are bounded by the 99% probability at 95% confidence one-sided 
tolerance limit estimated for the population, using a properly fit statistical distribution.  

c. A minimum of 20 specimens, distributed according to the lot requirements found in 
section 6.5 of this NASA Technical Standard, is required to initially establish material allowables. 

d. Material allowables incorporate the minimum CoV requirements of section 6.11.3 of this 
NASA Technical Standard. 

e. The property database is maintained by the CEO and updated on a periodic basis as 
additional data become available. 

f. Test and data analysis methodologies, except as noted in this requirement, follow the 
intent of the CMH-17 guidelines for static tensile property development. 

[Rationale:  Assumptions that shear properties will follow from isotropic continuum rules is not 
appropriate for AM materials that are prone to anisotropy and planes of reduced shear capability.] 


The small quantity of test specimens for shear properties relies on an assumption that these 
properties can leverage the tension and/or compression tests through ratio methods. If the 
variability demonstrated by the shear tests is not comparable to the tension/compression data, then 
more tests will typically be needed for an independent evaluation.  

 Flexural Properties 

[AMR-93]  For Class B parts manufactured using material with plastic tensile strain capability less 
than 3%, the flexural strength shall be evaluated, if required, for the following scenarios: 

a. If used in structural assessment, providing confirmation of design criteria and structural 
assessment methods. 

b. If used as a process control indicator, providing criteria for process qualification and 
production process monitoring. 

[Rationale:  Flexural properties are valuable indicators of capability, particularly for materials 
with asymmetry in tension and compression behavior and capability. This property can be used as a 
convenient process monitoring evaluation.] 

The use of flexural properties directly in design is less common than for use as a process control 
indicator. The statistical treatment of the data is not specified, but when implemented, the statistical 
significance of the data is expected to be commensurate with its use. 

 Fatigue Material Allowables and Design Values 

[AMR-94]  For Class B parts, when required for structural assessment or by the customer, the MPS 
for AM polymer materials shall include material allowables and/or design values for fatigue 
developed in accordance with the intent of the requirements in sections 6.11.4.4 and 6.11.4.5 of this 
NASA Technical Standard, with appropriate accommodations for polymeric material test standards 
and test methods. 

[Rationale:  Fatigue properties are critical to AM part integrity. There are currently no other 
sources providing these AM material characterization requirements.] 

It is important that the fatigue curve basis be consistent with the analytical methodology prescribed 
by governing structural requirements. 

 Fracture Mechanics 

For Class B applications in low ductility polymeric materials, evaluation of defect resistance due to 
fracture is highly recommended, particularly if there are preferential planes of low ductility. 


 Sustained Load Creep Deformation and Stress Cracking 

[AMR-95]  For Class B parts, if applicable to part design and required for structural assessment, the 
material response under sustained load conditions leading to creep mechanisms, crazing, or stress 
cracking shall be evaluated from AM material produced to an appropriate QMP, with lot 
requirements per section 6.5 of this NASA Technical Standard. 

[Rationale:  Stress rupture and creep properties vary with material product form; characterization 
of these properties is required in the AM product form.] 

This may be considered a bounding case of viscoplastic rate effects for static load conditions. The 
statistical significance of these properties is not specified. Conservatism is expected to be 
maintained either through bounding the material response or through generous factors applied in 
the structural assessment. 

 Joining 

[AMR-96]  For Class B parts, material properties for joining polymer AM products shall be 
developed to a statistical significance comparable to the base AM material properties using AM 
product manufactured from the same QMPs and incorporated into the applicable MPS. 

[Rationale:  Properties vary with material product form; characterization of these joining 
properties is required in the AM product form.] 

Joining of polymeric AM parts includes adhesive bonding as well as processes that affect the AM 
material directly (e.g., chemical or friction joining). 

 PART PRODUCTION PLAN (PPP) 

[AMR-97] A PPP for each AM part shall be developed by the CEO to address all requirements of 
this section, subject to review and approval by NASA. 

[Rationale:  The PPP is required for two primary purposes. First, the PPP serves as a mechanism 
to define process controls unique to a particular part design/build, capturing those process criteria 
that are not on the drawing. Second, the PPP serves as the primary means of communication of the 
part production intent and the level of risk associated with the AM part.] 

The PPP is intended to be a configuration-controlled document developed by the CEO that conveys, 
in a concise manner, the full intent for the design, production, and use of the AM part. The 
combined content of the engineering drawing, the PPP, and the AMCP is used to establish the 
complete production engineering controls governing the execution of all steps in the part production 
process. 


The form and format of the PPP are not specified. They should be adapted to suit the prevailing 
engineering and quality control documentation system of the CEO. The PPP should be a self-
substantiating document; but when needed to streamline the document, the PPP may reference 
other configuration-controlled documentation that is available to NASA on request. 

The method of approval for the PPP by NASA may be adapted to suit the contractual system 
established between NASA and the CEO. 

For Class C parts, the PPP need only include a part classification rationale and witness testing. 

7.1 Part-Specific Information 

[AMR-98]  For Class A and Class B parts, the PPP shall list the following minimum general 
information, or may reference other configuration-controlled documentation that is available to 
NASA on request: 

a. Drawing number and part name. 

 b. Illustrations and/or CAD model views (with scale). 

 c. The purpose of the part in context to the system. 

 d. The operational environments (e.g., temperatures, fluids, radiation, etc.).  

 e. Referenced build file name contained in the digital thread. 

 f. Material (including material specifications, if applicable): 

(1) Feedstock material specification. 
(2) Part material specification (or equivalent). 

 g. Identification of the QMP specified for production. 

 h. Identification of a specific MPS for the associated material used for part assessment, 
including influence factors, if applicable. 

 i. Serialization, part marking, and methodology for tracking individual parts, if applicable. 

 j. Cleanliness, if special considerations or requirements apply (e.g., oxygen service, optical 
surfaces, delicate electronics, etc.).  

 k. Qualification plan, when applicable. 


[Rationale:  This information is necessary to communicate the proposed configuration of the AM 
part to NASA and provide an objective comparison with the final build configuration for the 
qualified part process (see section 8 in this NASA Technical Standard)]. 

Revision numbers or dates for the above items do not need to be included in the PPP. If they are 
included, revisions to the above do not require re-review and approval of the PPP by NASA unless