What types of testing occur within a materials testing lab?

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Accepted Answer

Materials testing: The basics

Materials science and its associated tests are largely considered a part of the applied science branch of sciences, as the study and testing of the properties of materials are put to use in the manufacture and construction of a wide variety of items. Testing methodologies can be divided into the analysis of physical, mechanical, chemical, and biological properties, with each test falling under the category of destructive or non-destructive. Testing of a material may involve one or more of these methodologies, and occasionally all of them may be used as part of a comprehensive analytical approach towards a material.^[1][2]

Material testing may happen under the umbrella of materials discovery and research, or materials quality/suitability testing. In the case of the former, computational methods may initially be used to search through existing materials databases, as well as virtually develop new material models for potential real-life development, before any actual real-world materials testing begins. In the case of the latter, the material is already discovered or created, and materials testing occurs to verify that a material’s properties are suitable or of sufficient quality for their intended purpose. Technological systems such as laboratory information management systems (LIMS) may be used in both cases to better manage the associated data and information coming from their associated materials science activities.

Materials testing is as diverse as the available material types and industrial applications of those material types. Material testing domains include:

Aerospace
Automotive
Carbon
Coatings, linings, and sealants
Construction and engineering
Insulation, foam, and composites
Lubricants and thickeners
Medical devices
Metals
Packaging and labeling
Paints and oils
Paper
Polymers and plastics
Raw materials
Reference materials
Rubbers
Electronics and energy devices
Textiles
Wood

Optimally, materials testing is performed by a laboratory that is accredited to a relevant set of standards and test methods, making materials testing more standardized and reliable, in turn adding confidence to any items made or constructed from those tested materials.

Materials testing types

As noted prior, the diversity in materials testing methods is immense. As such, it’s difficult to address all of them in an FAQ. That said, this article will provide examples of destructive and non-destructive test methods across the four categories of test properties: physical, mechanical, chemical, and biological. (Note that in a few cases, a test might be destructive or non-destructive, depending on the particulars, for example as found with hardness, thickness, and crimp (length) testing, which are physical tests.^[3][4][5][6] However, also note that physical tests aren’t commonly destructive, and the classification of a biological test as destructive or non-destructive can be challenging.) Real-world examples from materials testing laboratories accredited to ISO/IEC 17025 are used to exemplify the broad set of test methods in use.

Physical

A physical property of a material represents the actual physical, inconstant state of the material, with its own set of measurable and observable properties, separate from the material’s chemical composition, mechanical, and biological properties.^[7]

Non-destructive physical tests include^{[8][9][10][11][12][13][14]}:

visual testing
magnetic particle testing
resonant ultrasound testing
color tolerance and difference
specular gloss
solar reflectance index
apparent density
water vapor transmission
ultrasonic defect testing
thermogravimetric analysis
infrared thermography
airflow resistance

Tests that can be both destructive and non-destructive physical tests include^[3][4][5][6]:

hardness
dry film and other coating thickness
yarn crimp percentage (length)

Mechanical

A mechanical property of a material represents the functional, inconstant state of the material, particularly in how it reacts when a load is applied to it. Measuring mechanical properties gives a better idea of the material’s realistic service life or performance under mechanical stresses.^[7] Mechanical testing is frequently destructive in nature.

Destructive mechanical tests include^{[7][11][15][16][17]}:

scratch adhesion testing
flattening testing
flaring testing
burst strength
tear strength
peel strength
bend testing
tensile bond testing
concentrated impact
compressive resistance
abrasion resistance

Chemical

A chemical property of a material represents how the material reacts under the duress of outward pressures, which fundamentally change the material into a different material over a period of time.^[18] As an example, one can turn to the principal of using a sacrificial anode to prevent the corrosion of a principle metal, with the anode being chemically altered into another substance rather than the principle metal. This method may be used if the principle metal’s chemical property of “corrosion resistance” is low.

Destructive chemical tests include^{[15][18][19][20]}:

corrosion resistance
flammability
galvanized coating weight
leaching

Non-destructive chemical tests include^[21][22][23]:

liquid dye penetration
chemical composition through spectrometry, spectroscopy, or X-ray fluorescence
surface tension
temperature-compensated viscosity

Biological

In the scope of testing quality and suitability of raw materials used in the production of an item, a biological property of a material represents how the material reacts to one or more aspects of a biological organism, or how a biological organism reacts to the introduction of the material. Examples of biological properties include^[24]:

toxicity, “the degree to which a material may permanently destroy or impair any part of biological organism;
bioinertness, the ability of some material to go unchanged and elicit biological activity upon introduction to a biological organism; and
bioactivity, the ability of a material to “elicit or modulate a favorable response” from one or more systems of a biological organism.

One school of thought has that in vitro testing of biological samples is non-destructive (as with bacterial endotoxins testing^[25]). However, one might argue that in some cases the in vitro biological sample being tested must be altered destructively, or even that microbes are living biological entities, which may get destroyed in specific bioburden test types.^[26] As such, these tests’ classification as “destructive” or “non-destructive” may be viewed with some skepticism.

Destructive biological tests include^[26][27][28]:

bioburden testing
antimicrobial effectiveness
microbial immersion

Non-destructive biological tests include^{[25][28][27][29][30][31]}:

bacterial endotoxin testing
sterility testing
cell and tissue characterization using ultrasound
bioburden testing

References

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