PCRDs per the QMP. 

It is recommended that properties not required for registering a candidate material process to the 
MPS still be measured and controlled when important to the design. An example is provided with 
respect to the fracture toughness of a polymeric material. Although a requirement is not placed for 
measuring this property of a polymer for successful MPS registration (by virtue of implied 
structural considerations of Class B parts), characterizing fracture toughness provides insight into 
plane-strain fracture behavior. To assess the correlating properties, conducting ASTM D5045 will 
indicate a polymer's rate of crack propagation through its plane-strain energy release rate. The 
applicability of this investigation varies with the polymer and may be more relevant to those 
exhibiting brittle fracture (e.g., a filled polyamide).  

For example, in metallic AM builds, four PCRDs are defined for each MPS:  ultimate tensile 
strength (UTS), yield strength, elongation, and fatigue life at a fixed cyclic stress condition. The 
choice of defined PCRDs may change with AM process and material depending on which properties 
are determined most useful to process control. The PCRDs and their associated acceptance criteria 
are best documented in a manner that allows for occasional revision and sustained use as witness 
specimen testing acceptance criteria for part acceptance. 

 Bootstrapping a QMP and MPS 

When new AM processes are first established, an MPS may not yet exist to conduct the registration 
process. In such cases, the material test data generated to produce the QMP are also used to 
generate the initial MPS (i.e., bootstrapping), and the QMP is registered to the new MPS by default. 


Additional data generated from the QMP are used to populate preliminary MPS PCRDs and other 
material properties to enable registration of additional QMPs. 

In these cases, the QMP can be executed with a single feedstock lot to create the initial MPS, but 
additional lot and variability requirements are governed by the MPS requirements in section 6 of 
this NASA Technical Standard. 

5.7 Qualified Material Process Record 

[AMR-60]  A candidate QMP shall become fully qualified (i.e., a QMP) when: 

a. A configuration-controlled record is established containing the complete definition of the 
candidate QMP and all necessary supporting information substantiating that the qualification 
requirements in section 5 of this NASA Technical Standard have been satisfied. 

b. The CEO has verified it to be complete and satisfactory. 

c. Items (a) and (b) are documented and controlled by the QMS. 

[Rationale:  The QMP is a core governing document of AM process control and, as such, has to be 
properly substantiated, approved, and documented.] 

See section 5.2 of this NASA Technical Standard for additional information regarding candidate 
material processes and unique QMPs. 

This requirement intends the following:  The CEO approves QMPs. Once approved and 
documented, a QMP record defines a fixed process such that changes are prohibited without formal 
reevaluation and approval. A QMP may be treated as proprietary information. NASA may review a 
QMP and its supporting data at any time. The development of candidate QMPs is typically the 
responsibility of the AM part producer. A partnership between the CEO and the AM part producer, 
if not the same entity, is required for successful implementation of these requirements. 

 MATERIAL PROPERTY SUITE (MPS) 

6.1 MPS for Class A and B Parts 

[AMR-61]  For Class A and B parts, an MPS shall be developed and maintained to substantiate the 
design and production of AM parts.  

[Rationale:  The four components of the MPS (i.e., material property data, material allowables and 
associated design values, PCRD, and SPC criteria) are required to integrate the fundamentals of 
reliable AM part design and production.]  


In an effort to maintain consistency with developing aerospace industry consensus in terminology, 
this NASA Technical Standard uses the terms “material allowable” and “design value” when 
referring to the properties of AM materials (see the definitions in section 3.2 of this NASA Technical 
Standard). Material allowable is used to represent the bulk properties of the AM material absent the 
influencing effects of environment, surface finish, or other factors affecting material performance. 
The material allowable is intended to include the fundamental sources of variability (e.g., feedstock 
lots, allowable variations in key process variables, heat treating, machine-to-machine and build-to-
build variability, and build-dependent microstructural variability), which may lead to differences in 
performance between specimen and parts. Note that, for brevity, the term “material allowable” is 
also occasionally used herein as a general term referring to statistically characterized material 
properties. The term “design value” represents a material property as applied to the AM part 
design to assess structural capability. In some situations, the material allowable is directly 
applicable to the design and, in such cases, the material allowable is used directly as the design 
value. In many cases, the material property used in the design assessment has to take into account 
factors that influence the material behavior, such as environment, surface quality, thin sections, or 
part-specific features. Design values that include these effects are often based on the material 
allowables through the application of a multiplicative “influence factor” or “scale factor” to alter 
the material allowable value to represent these effects. A temperature adjustment of the material 
allowable to create a design value to assess the part at operational temperature is the most common 
application of this. In some cases, design values may be generated with statistical basis independent 
of the material allowable. This is most common when the influence factor being assessed for the 
design value represents a new and significant source of variability not represented in the 
assessment of the material allowables. In these cases, it is important that the independent 
assessment of a design value also include the sources of variability represented in bulk material. 

Note:  Data collected during the development of a QMP may be included in the MPS. 

Requirements and further discussion on the development of material allowables and design values 
are in section 6.11.1 of this NASA Technical Standard. 

6.2 Material Properties for Class C Parts 

[AMR-62]  For Class C parts, all required material properties needed to substantiate the 
manufacturability of the design and classification of the part shall be documented through the MUA 
process or the PPP, but may be of typical basis.  

[Rationale:  Understanding of material behavior is required for Class C components to ensure they 
are properly placed in Class C and perform their intended purpose.] 

Material properties for Class C parts may be at a design basis (i.e., bounded statistically or by 
engineering judgment) or of typical basis (i.e., average values). 

An MPS meeting the requirements for Class A and B parts is also acceptable for Class C parts. 


6.3 MPS Approval  

[AMR-63]  An MUA per NASA-STD-6016 shall be submitted for MPS review and approval by 
NASA and, at a minimum, address the following: 

 Documentation substantiating the development, implementation, and maintenance of the 
MPS (for Class A and B parts). 

 Documentation that addresses, at minimum, the requirements given in sections 6.4 
through 6.10 of this NASA Technical Standard, and all subsections relevant to the applicable 
material allowables and associated design values in sections 6.11.2 and 6.11.5 of this NASA 
Technical Standard. 

 For Class A and B parts, material allowables and associated design values, PCRDs, and 
all other supporting data of the MPS are made available for NASA review as requested. 

 For Class C parts, material properties are documented as required to substantiate the 
design and classification. 

[Rationale:  Material properties specific to the AM product form and its unique characteristics are 
required for reliable structural design assessment. Maintaining a suite of material allowables and 
associated design values along with the supporting data provides the basis for criteria used to 
monitor process control.] 

Except for projects with few AM parts, the MUA addressing the MPS is usually part agnostic. 
Instead of addressing part-specific properties, the MUA covers the methodology for the 
development and maintenance of the MPS for use with any appropriate part. A separate, part-
specific MUA is required when lot-provisional material allowables and associated design values 
are used for Class B part production (see section 6.5 in this NASA Technical Standard). 

In this NASA Technical Standard, material properties have a role in both design and process 
control and are maintained as an MPS. The MPS consists of four entities: 

(1) Material property data developed for a specific AM material and condition. 

(2) The material allowables and design values derived from the data used in structural 
assessment. 

(3) PCRDs derived from the data to describe the material’s nominal performance and 
variability.  

(4) SPC criteria based on the PCRD used in evaluating the AM process to ensure the 
integrity of the material allowables is maintained. 


The collection of mechanical properties in this NASA Technical Standard was given a unique name 
(i.e., MPS) because it serves two purposes:  (1) creating a reference of expected performance for 
use in process control and (2) establishing material allowables and associated design values. For 
conventional materials, the statistical relationship between process control and material allowables 
is evaluated at a moment in time and rarely reexamined. In contrast, in the methodology of this 
NASA Technical Standard, new process control data are continuously monitored and compared 
with the reference data to demonstrate that the process is not changing. Activities that use these 
SPC constructs include witness testing, registration of newly qualified AM processes through 
equivalency evaluation, and requalification of AM processes after machine maintenance or updates. 
To meet the intent of this requirement, an MPS has to be capable of accommodating new data in an 
organized manner and maintaining the data traceability over time. While material allowables are 
expected to remain static, reevaluation of the MPS data is a recurring task to reaffirm the validity of 
the material allowables and perform equivalency tests for QMP registration and other ongoing 
needs. 

When developed as required by this NASA Technical Standard and implemented in conjunction with 
ongoing process control monitoring schemes, the material allowables and associated design values 
in the MPS meet the intent of the requirements for material property reliability for use in structural 
analysis. 

The MUA process in NASA-STD-6016 is the prescribed method for documenting and obtaining 
approval for the MPS because neither material allowables nor the methodology for developing AM 
material allowables are currently covered by the MMPDS or CMH-17, Composites Materials 
Handbook-17, so the MPS will require an MUA (NASA-STD-6016, MPR 38). Other means of 
documenting and approving the MPS, such as a prescribed data requirement serving the purpose, 
are acceptable when defined in the AMCP. 

6.4 Process Control in Material Property Development 

[AMR-64]  For Class A and B parts, documented process controls shall be implemented on any AM 
build used to create material for characterization, including the use of a QMP and witness testing 
with specimens and acceptance criteria equivalent to a Class B1 part, per Tables 5 and 6.  

[Rationale:  Material properties are reliable only if generated on material produced under defined 
and controlled processes.] 

This requirement applies to any build used to produce material to support the data population of the 
MPS for a given AM process or for developing process control baseline data. A controlled AM 
process is a prerequisite to the development of material properties; characterization builds follow a 
QMP developed per section 5 of this NASA Technical Standard (see section 5.6.1). The process 
control requirements and prerequisites for producing AM materials for characterization are similar 
to those required for parts. 


6.5 Lot Variability Impact on Material Allowables 

[AMR-65]  Each material allowable within an MPS shall be designated either lot-mature when 
based on the minimum unique chemistry feedstock lot quantities in Table 18, Required Lot 
Quantities for Lot-Mature Metal MPS Properties, and Table 19, Required Lot Quantities for Lot-
Mature Polymeric MPS Properties, or lot-provisional if not, where: 

 A lot-mature material allowable is applicable to material used in parts of all classes.  

 A lot-provisional material allowable is applicable to material used in Class B parts that 
are built with a feedstock lot directly represented in the MPS and that have an approved, part-
specific MUA. 

 Lot-provisional material allowables are applicable to material used in Class C parts 
without feedstock restrictions or a part-specific MUA. 

[Rationale:  Variations in the chemistry and morphology of the feedstock, even within specification 
limits, result in variability in the performance of material produced using the AM process; so this 
source of variability has to be incorporated into design values for reliable structural assessment.] 

See section 6.11.3 in this NASA Technical Standard for additional insight into how lot-mature and 
lot-provisional properties impact material allowables and the integrated structural integrity 
rationale for any given part. 

Note that the same material input lot (e.g., heat number from a primary mill) can be used to make 
many different feedstock lots. 
Table 18—Required Lot Quantities for Lot-Mature Metal MPS Properties 
Properties 
Feedstock Lots 
(nominally balanced*) 
Build/Heat Treat Lots 
(nominally balanced*) 
Physical and constitutive 3 5 
Tensile 5 10 
Secondary 3 5 
Fatigue 5 10 
Fracture mechanics 3 5 
Stress rupture/creep 3 5 
* Nominally balanced lot contributions as described in commentary. 


Table 19—Required Lot Quantities for Lot-Mature Polymeric MPS Properties 
Properties Feedstock Lots  Build Lots 
Physical and constitutive 3 5 
Tensile/compression† 5 10 
Shear 5 10 
Flexural 5 10 
Fatigue 5 10 
Creep/sustained load 5 10 
† Including notch testing, if required 

Lot-provisional material allowables containing fewer lots than required in Tables 18 and 19 (as few 
as one lot) may be used for Class B parts with an approved, part-specific MUA. To be approved, the 
MUA is expected to substantiate that the lot-provisional material allowables have a quantity of data 
sufficient to make an informed engineering assessment of the quality and statistical significance of 
the material allowables. The MUA is expected to demonstrate that the feedstock lot used in the 
production of parts has a meaningful representation in the MPS, typically taken as a minimum of 
15% of the population. 

In Table 18, a “nominally balanced lot contribution” means that each lot has sufficient 
representation in the total population to be influential in contributing to the evaluation of 
variability, and that no single lot, or small quantity of lots, constitutes a majority of the data 
population. For example, an acceptable working definition of nominally balanced lot contributions 
would be each lot contributing 10 to 30% of the data population when the number of lots is ≤5, and 
each lot contributing 5 to 15% of the data population when the number of lots is between 5 and 10. 
Similar ratios would follow as lot quantities grow beyond 10. Other interpretations for nominally 
balanced lot contributions are allowed if substantiated in the MPS documentation. 

The MPS may contain both lot-mature and lot-provisional material allowables. It is natural for a 
developing database to contain differing quantities of data used for determining individual material 
allowables and associated design values. 

Feedstock lot variability requirements are recommended but not required for Class C parts. 


6.6 Used Feedstock Lot Controls 

[AMR-66]  When printing Class A and B parts using AM processes capable of feedstock reuse, 
limiting metrics for feedstock reuse shall be established and implemented to ensure the following: 

a. The effects of reuse on material performance are either demonstrated as negligible or 
material property data representing the limiting reuse state are incorporated directly into the MPS 
population. 

b. Parts are not built with feedstock exceeding the reuse limits. 

c. The methodology for incorporating the influence of feedstock reuse into the design 
values of each MPS is described as part of the MUA substantiating the methodology of the MPS 
development. 

[Rationale:  For AM processes where feedstock reuse is feasible (e.g., PBF), the AM process has 
the potential to degrade the feedstock with continued reuse. Degradation mechanisms vary by 
material and AM process; an understanding of feedstock reuse effects is required, and the AM 
process is to be controlled to preclude feedstock reuse from affecting part quality.] 

Examples of feedstock degradation by reuse include introducing contaminants (e.g., oxygen or 
combustion by-products), or changing a powder feedstock’s morphology and rheology 
characteristics. The effects of feedstock reuse are material specific; the intent is to evaluate 
feedstock reuse effects on material properties using only material procured to the feedstock 
specification identified by the QMP. 

The CEO, in collaboration with the AM part producer, is responsible for ensuring feedstock reuse 
metrics are defined and implemented in accordance with this requirement. The expectation is that 
the efficacy of the reuse metrics is substantiated through a dedicated test plan and subsequent data 
that characterize the influence of feedstock reuse on material performance or demonstrate that 
powder at the limiting reuse metric has a negligible influence on material performance. 

6.7 Influence Factors 

This NASA Technical Standard uses the term “influence factor” to describe any factor that has the 
capacity to alter the baseline performance of the material (i.e., the material allowable). These 
factors include those commonly evaluated for other material product forms, such as environment 
(e.g., temperature, humidity) or surface condition. For AM materials, influence