ASTM F1864-05(2010)
(Test Method)Standard Test Method for Dust Erosion Resistance of Optical and Infrared Transparent Materials and Coatings
Standard Test Method for Dust Erosion Resistance of Optical and Infrared Transparent Materials and Coatings
SIGNIFICANCE AND USE
All materials on exterior aircraft surfaces are subject to abrasion from airborne particles of various sizes and shapes. Transparent materials are particularly vulnerable to abrasion, since their performance is based on their ability to transmit light with a minimal amount of scatter. Scratches, pitting, and coating removal and delamination as a result of abrasion may increase scatter, reduce transmission, and degrade the performance of transparent materials. Visually transparent materials are required for pilot and air crew enclosures, such as canopies, windshields, and viewpoints. Materials transparent in the IR region (8 to 12 μm) are required for tracking, targeting, and navigational instrumentation.
This test method is intended to provide a calibrated and repeatable means of determining the relative abrasion resistance of materials and coatings for optical and IR transparent materials and coatings. The test parameters for this test method can be directly related to dust cloud densities and velocities to which transparent materials are exposed in the field.
SCOPE
1.1 This test method covers the resistance of transparent plastics and coatings used in aerospace windscreens, canopies, and viewports to surface erosion as a result of dust impingement. This test method simulates flight through a defined particle cloud environment by means of independent control of particle size, velocity, impact angle, mass loading, and test duration.
1.2 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.
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Standards Content (Sample)
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Designation: F1864 − 05(Reapproved 2010)
Standard Test Method for
Dust Erosion Resistance of Optical and Infrared Transparent
Materials and Coatings
This standard is issued under the fixed designation F1864; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision.Anumber in parentheses indicates the year of last reapproval.A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope 3.1.2 mean IR transmission, n—for the purposes of this
standard, the average percentage of light transmitted by a
1.1 This test method covers the resistance of transparent
material in the 8- to 12-µm bandwidth.
plastics and coatings used in aerospace windscreens, canopies,
3.1.3 sweep time, n—the time required for one translation
and viewports to surface erosion as a result of dust impinge-
pass.
ment. This test method simulates flight through a defined
particlecloudenvironmentbymeansofindependentcontrolof
3.1.4 translation pass, n—the translation of the specimen
particle size, velocity, impact angle, mass loading, and test
platformfromtheverticalorhorizontallimittothecorrespond-
duration.
ing vertical or horizontal limit.
1.2 This standard does not purport to address all of the
3.1.5 translation cycle, n—the translation of the specimen
safety concerns, if any, associated with its use. It is the
platformfromtheverticalorhorizontallimittothecorrespond-
responsibility of the user of this standard to establish appro-
ingverticalorhorizontallimitandbacktotheinitialverticalor
priate safety and health practices and determine the applica-
horizontal limit. Two translation passes are equivalent to one
bility of regulatory limitations prior to use.
translation cycle.
3.2 Symbols:
2. Referenced Documents
2.1 ASTM Standards:
A = reference surface area of specimen platform (cm ),
D618Practice for Conditioning Plastics for Testing
s
C = simulated cloud concentration (g/m ),
D1003Test Method for Haze and Luminous Transmittance
c
h = percent haze before exposure,
of Transparent Plastics o
h = percent haze after exposure,
D1193Specification for Reagent Water e
m˙ = rate of particle mass impacting the reference surface
p
E11Specification forWovenWireTest Sieve Cloth andTest
area (g/min),
Sieves
m˙ = incremental mass loading (g/cm ),
i
E168Practices for General Techniques of Infrared Quanti-
m = total mass loading (g/cm ),
T
tative Analysis (Withdrawn 2015)
N = number of increments,
V = particle impact velocity (m/s),
p
3. Terminology
t = sweep time(s),
s
3.1 Definitions of Terms Specific to This Standard: T = optical or mean infrared (IR) transmission after expo-
e
sure (%),
3.1.1 mass loading, n—the mass of dust per unit of total
T = optical or mean IR transmission before exposure (%),
exposed surface area (including the sample holder) that im-
o
α = impact angle (normal incidence=90°),
pinges on the specimens.
∆t = exposure time (min) for loading increment i,
i
φ = incremental dust load (g/cm ) for loading increment i,
i
This test method is under the jurisdiction of ASTM Committee F07 on
Φ = total dust load (g/cm ),
Aerospace andAircraft and is the direct responsibility of Subcommittee F07.08 on
∆h = change in percent haze, and
Transparent Enclosures and Materials.
Current edition approved May 1, 2010. Published June 2010. Originally
∆T = change in optical or IR transmission.
approved in 1998. Last previous edition approved in 2005 as F1864–05. DOI:
10.1520/F1864-05R10.
4. Summary of Test Method
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
4.1 This test method consists of: (1) measuring and record-
Standards volume information, refer to the standard’s Document Summary page on
ing the light transmission properties, at visual or infrared
the ASTM website.
wavelengths, of test coupons; (2) mounting the coupons in a
The last approved version of this historical standard is referenced on
www.astm.org. test fixture; (3) exposing the coupons to a dust particle stream;
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
F1864 − 05 (2010)
and (4) remeasuring the light transmission properties to deter- 5.2 This test method is intended to provide a calibrated and
mine changes in these properties. repeatable means of determining the relative abrasion resis-
tance of materials and coatings for optical and IR transparent
4.2 The dust particle stream simulates flight at a specified
materialsandcoatings.Thetestparametersforthistestmethod
velocitythroughadustcloudofspecifieddensity.Simulationis
can be directly related to dust cloud densities and velocities to
accomplished through control of particle size distribution,
which transparent materials are exposed in the field.
mean particle velocity, particle mass flow rate, and angle of
impact.
6. Apparatus
4.3 The degree of abrasion is measured by the amount of
6.1 Dust Erosion Abrader, as illustrated in Fig. 1. The test
change in haze and luminous transmittance for materials
apparatus simulates flight through dust environments by blow-
transparent in the visual wavelengths and by the amount of
ing crushed silica particles, at a controlled mass flow rate and
change in IR spectral transmission for materials transparent in
velocity, onto samples that are stationary in the direction of
the infrared wavelengths.
particle flow.The dust erosion abrader consists of four distinct
subsystems: transport gas system, dust particle delivery
5. Significance and Use
system, dust velocity calibration system, and specimen plat-
5.1 All materials on exterior aircraft surfaces are subject to form.
abrasion from airborne particles of various sizes and shapes. 6.1.1 The transport gas system carries the dust particles at
Transparent materials are particularly vulnerable to abrasion, specified velocity. The transport gas for the particles may be
since their performance is based on their ability to transmit dry air or nitrogen. The transport gas shall be controlled by a
light with a minimal amount of scatter. Scratches, pitting, and system of precision regulators and pressure transducers and
coating removal and delamination as a result of abrasion may routed through a nozzle which produces stable flow for the
increase scatter, reduce transmission, and degrade the perfor- particle sizes and velocities of interest. Dust particles are
mance of transparent materials. Visually transparent materials accelerated to target velocities in a circular jet formed by the
arerequiredforpilotandaircrewenclosures,suchascanopies, expansion of compressed gas in the nozzle. The nozzles
windshields, and viewpoints. Materials transparent in the IR conforming to Fig. 2 have been shown to produce stable flow
region (8 to 12 µm) are required for tracking, targeting, and for inlet pressures in the range 5.50 to 620 kPa (0.800 to 90.0
navigational instrumentation. psi). The nozzle consists of converging-diverging sections,
FIG. 1 Dust Erosion Chamber
F1864 − 05 (2010)
FIG. 2 Recommended Nozzle Configuration
which accelerate the gas phase to supersonic speeds, and a possesscontrolinstrumentationseparatefromthetransportgas
constant diameter extension which provides sufficient resident control system so that mass flow rate of the dust can be
time for particle acceleration. Fig. 3 shows typical stable controlled independent of the transport gas velocity.
velocities that can be achieved using the nozzle in Fig. 2. The 6.1.3 The dust velocity calibration system shall consist of a
nozzle mount shall include adjustments for convenient access noninvasive velocity measurement system (VMS) such that
to the specimen platform during mounting of the specimen particle velocity may be calibrated to transport gas pressure
holder and for positioning the nozzle a distance of 25.4 mm and dust mass flow rate. The laser doppler velocimeter (LDV)
(1.00 in.) from the specimen after mounting. shown in Figs. 5 and 6 has been demonstrated to provide the
6.1.2 The dust particle delivery system directs particles into requiredvelocitymeasurements.In-situmonitoringofvelocity
the transport gas stream. The delivery system shall deliver during dust exposure is recommended. However, if the size or
uniform and consistent mass flow over the range of 0.200 to configuration of the noninvasive VMS prohibits in-situ
10.0 g/min. The system consists of a pressurized holding monitoring, pre- and post-exposure calibration shall be con-
container for the dust and a mechanism for directing the dust ducted to ensure that the velocity/pressure calibration has
into the transport gas stream.Ascrew feeder system housed in remained valid through the test.
apressurizedplenum(Fig.4)hasbeendemonstratedtoprovide 6.1.4 The specimen platform and test bed consists of stages
the required mass flow. The particle delivery system shall and fixtures onto which test specimens and the nozzle are
F1864 − 05 (2010)
FIG. 3 Typical Velocity/Pressure Profile for Fig. 2 Nozzle
FIG. 5 Laser Doppler Velocimeter Calibration
FIG. 4 Screw Feeder and Pressurized Plenum
Translation rates shall be adjustable from 0 to 30 translation
mounted.The test bed shall include adjustments such that dust cyclesperminutehorizontallyand0to4translationcyclesper
particle incidence angles range from normal to 70° off-normal. minute vertically. The translation range shall be sufficient to
Because the particle stream is substantially smaller than the permittheoutermostspecimenstotranslatecompletelypastthe
specimen holder, the specimen platform shall translate both dust jet in all directions. The specimen platform shall accom-
horizontallyandverticallythroughtheparticlestreamtoensure modateavarietyoftestsamplegeometries.Samplesrangingin
uniformcoverageofallspecimens.Screw-typemechanismsor size from 25.4 mm (1.00 in.) in diameter to 152 mm (6.00 in.)
stepper motors are recommended for platform translation. square have been exposed in the test bed shown in Fig. 7. The
F1864 − 05 (2010)
FIG. 6 Laser Doppler Power Supply and Instrumentation
FIG. 8 Typical Frontal Mask
FIG. 7 Dust Erosion Test Bed with Programmable Stepper Mo-
tors
FIG. 9 Continuous Flow Vibrating Sieve
specimen platform shall include adjustment for convenient
mounting of samples. Sample holders shall include a frontal
mask to control the abraded area and prevent abrasion near 6.3 Integrating Sphere Photoelectric Photometer, as de-
sample edges. The frontal mask shall include tapered edges scribed in Test Method D1003, shall be used to measure the
(Fig. 8) to direct the dust flow onto the sample. light transmitted and scattered by the abraded surface of
optically transparent materials and coatings.
6.2 A wire-cloth particle sieve shall be used to obtain
specific particle-size ranges.Acontinuous flow vibrating sieve 6.4 Fourier Transform Infrared (FTIR) Spectrometer shall
system (Fig. 9) is recommended for optimum and efficient be used to measure the IR transmission properties of IR
sieving of bulk sand. Sieve nominal dimensions and permis- transparent materials and coatings. The spectrometer shall be
sible variations shall comply with the U.S.A. Standard Test capable of measuring percent transmission in the 8- to 12-µm
Sieves Standard Series as detailed in Specification E11. bandwidth. A number of self-contained commercial FTIR
F1864 − 05 (2010)
systems existing on the market have been demonstrated to ment if used. (Warning—Sieving of the bulk sand can create
provide the required measurements. Spectrometers used in this small airborne dust particles that can irritate the nose, throat,
test method shall comply with applicable sections of Practice and lungs. Wear a breathing mask appropriate for the particle
E168. size being sieved to minimize the hazard of inhaling airborne
dust particles.)
7. Materials and Reagents
9.2 Fill the pressurized holding chamber with the dust
7.1 Purity of Water—Unless otherwise indicated, references
required for the exposure run.
to water shall be understood to mean reagent water as defined
9.2.1 Iftheholdingcontainerrequiressimplereplenishment
by Type II of Specification D1193.
of dust, remove the chamber lid and add the required amount
of dust. Check all pressure seals for damage, and replace if
7.2 Crushed Silica Sand—Thedustparticlesshallconsistof
damaged or worn. Carefully replace the lid, ensuring the
crushed silica sand. The sand shall be dry, nonclogging, and
chamber is adequately sealed.
have corners and edges that have not been rounded by other
9.2.2 If the subsequent exposure run requires exchanging
than the crushing process. Bulk dust particle sizes shall be
dust sizes, remove the chamber lid and remove the dust from
uniformly distributed in the range 10 to 250 µm.
the previous run. Thoroughly clean all chamber and delivery
7.3 Compressed Air or Nitrogen—Thetransportgasshallbe
system components (disassemble if necessary) to remove all
dry and pressurized to a minimum of 827 kPa (120 psi) at the
traces of the previous dust. Wipe holding chamber surfaces
source.
with a lint-free towel dampened with isopropyl alcohol solu-
7.4 Isopropyl Alcohol Solution—Mix isopropyl alcohol
tion. Add the required amount of dust for the next exposure
(C H OH) with water in a volumetric ratio of 1:1.
3 7 run. Check all pressure seals for damage, and replace if
damaged or worn. Carefully replace the lid, ensuring the
8. Test Specimens
chamber is adequately sealed.
8.1 Optically Transparent Materials—Test specimens shall
be clean flat samples of the material or substrate/coating
10. Calibration and Standardization
system to be evaluated. Sample dimensions, including
10.1 Pressure in Transport System and Dust Delivery
thickness, may be of any convenient dimension that can be
System—Calibrate transducers with 0- to 1.00-MPa (0- to
accommodated by the specimen platform and test bed, with a
150-psig) range in accordance with manufacturer specifica-
2 2
minimum exposed surface area of 363 mm (0.750 in. ).
tions. If none are available, calibrate the transducer by com-
Samplesranginginsizefrom25.4to152mm(1.00to6.00in.)
parison to a secondary standard. Connect the pressure trans-
square have been found to accommodate most test require-
ducer and a high resolution dial gage (0 to 1.5 MPa/0 to 220
ments. Sides of samples shall be substantially plane and
psig) to the holding chamber. Zero the transducer, and pres-
parallel. Edge chipping and coating delamination res
...
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