July 2017 

NASA/TP–2017-219644 

Simulated Space Environment Effects on a 

Candidate Solar Sail Material 

Jin Ho Kang 

National Institute of Aerospace, Hampton, Virginia 

Robert G. Bryant and W. Keats Wilkie 

Langley Research Center, Hampton, Virginia 

Heather M. Wadsworth 

Virginia Polytechnic Institute and State University, Blacksburg, Virginia 

Paul D. Craven, Mary K. Nehls, and Jason A. Vaughn 

Marshall Space Flight Center, Huntsville, Alabama 
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July 2017 

NASA/TP–2017-219644 

Simulated Space Environmental Effects on 

Candidate Solar Sail Material 

Jin Ho Kang 

National Institute of Aerospace, Hampton, Virginia 

Robert G. Bryant and W. Keats Wilkie 

Langley Research Center, Hampton, Virginia 

Heather M. Wadsworth 

Virginia Polytechnic Institute and State University, Blacksburg, Virginia 

Paul D. Craven, Mary K. Nehls, and Jason A. Vaughn 

Marshall Space Flight Center, Huntsville, Alabama 
Available from: 

NASA STI Program / Mail Stop 148 

NASA Langley Research Center 

Hampton, VA 23681-2199 

Fax: 757-864-6500 

The use of trademarks or names of manufacturers in this report is for accurate reporting and does not constitute an 

official endorsement, either expressed or implied, of such products or manufacturers by the National Aeronautics and 

Space Administration.
 

Contents 

Abstract...................................................................................... 1

Nomenclature............................................................................... 1

 Symbols.................................................................................... 1

 Subscripts................................................................................ .. 1

 Acronyms.................................................................................. 1

1. Introduction............................................................................. 2

2. Experimental............................................................................ 2

2.1. Materials............................................................................... 2 

2.2. Electron Irradiation Tests............................................................ 3

2.3. Thermal Analysis..................................................................... 3

2.4. Thermal Aging Tests................................................................. 3

2.5. Mechanical Property Tests.......................................................... 3

3. Results................................................................................... 4 

3.1.Electron Irradiation.................................................................... 4

3.2.Thermal Aging Tests.................................................................. 5

3.3.Simulated Impact Damage Effects on Mechanical Properties................... 6

4. Conclusions............................................................................. 7

Acknowledgements........................................................................ 7

 References................................................................................... 8

i
 

List of Tables 

Table 1. Physical properties of the metallized PEN................................... 9

Table 2. Tear physical properties of the metallized PEN............................. 9

ii
 

List of Figures 

Figure 1. Molecular structure of PEN............................................................ 10 

Figure 2. (a) Sample preparation and (b) setup during testing for DENT configuration 

(Mode I tear test)....................................................................... 10

Figure 3. (a) Sample configuration and (b) setup during testing for Mode III tearpropagation resistance................................................................... 11

Figure 4. Setup for tensile test of metallized PEN film with a 2 mm die-cut hole to 

simulate potential impact damage.................................................... 11 

Figure 5. Metallized PEN films on the sample holder plate (a) before electron 

irradiation and (b) after electron irradiation......................................... 12 

Figure 6. SEM image of the aluminum coating surface of the metallized PEN film 

(a) before electron irradiation and (b) after electron irradiation.................. 12

Figure 7. Tensile properties of metalized (a) control PEN and (b) electron irradiated 

PEN films. Each color represents one of 5 tensile test specimens................ 13

Figure 8. DMA curves of control and electron irradiated PEN films....................... 14

Figure 9. DSC thermograms of control and electron irradiated PEN films................. 14

Figure 10. FT-IR spectra of (a) control and (b) electron irradiated PEN films............ 15

Figure 11. CTE of raw PEN films and metallized PEN films............................... 16

Figure 12. Appearance of metallized PEN films after thermal aging test at (a) room 

temperature, (b) 100C, (c) 125C, (d) 150C, (e) 175C, (f) 200C, 

(g) 225C and (h) 300C............................................................... 17

Figure 13. Spectra reflectance of metallized PEN films after thermal aging at various 

temperatures from RT to 300C...................................................... 18 

Figure 14. Mechanical properties of metallized PEN films after thermal aging at 

various temperatures of room temperature (control), 200 and 225C............ 18

Figure 15. Mode I tear fracture property of metallized PEN films. (a) Load vs. 

displacement profile and (b) specific total work of fracture (wf) vs. 

ligament length (L)..................................................................... 19 

Figure 16. Tensile properties of metallized PEN films with simulated impact damage.. 20 

iii
Abstract 

For long duration missions of solar sail vehicles, the sail material needs to survive the harsh 

space environment as the degradation of the sail material determines its operational lifetime. 

Therefore, understanding the effects of the space environment on the sail membrane is essential 

for mission success. In this study, the effect of simulated space environments of ionizing radiation 

and thermal aging were investigated. In order to assess some of the potential damage effects on 

the mechanical, thermal and optical properties of a commercial off the shelf (COTS) polyester 

solar sail membrane. The solar sail membrane was exposed to high energy electrons (about 70 keV 

and 10 nA/cm2), and the physical properties were characterized. After about 8.3 Grad dose, the 

tensile modulus, tensile strength and failure strain of the sail membrane decreased by 20 to 95%. 

The aluminum reflective layer was damaged and partially delaminated but it did not show any 

significant change in solar absorbance or thermal emittance. The mechanical properties of a precracked sample, simulating potential impact damage of the sail membrane, as well as thermal aging 

effects on metallized PEN (polyethylene naphthalate) film, will be discussed. 

Nomenclaure

Symbols

χc crystallinity

Hf heat of fusion

wf specific total work of fracture

we specific essential work of fracture

wp non-essential work (plastic deformation) 

β proportionality constant (plastic zone shape factor) 

L ligament length

Subscripts

f fusion (or melting)

e essential contribution

p plastic deformation (non-essentional contribution)

Acronyms

ASTM American Society for Testing Materials

COTS Commercial Off the Shelf

CTE Coefficient of Thermal Expansion

DENT Double-Edge Notched Tension

DMA Dynamic Mechanical Analyzer

DSC Differential Scanning Calorimetry

EWF Essential Work of Fracture

FT-IR Fourier Transform Infrared

HRSEM High-Resolution Scanning Electron Microscope

1
2 

IR Infrared

MD Machine Direction

MDSC Modulated Differential Scanning Calorimeter

MSFC Marshall Space Flight Center

NASA National Aeronautics and Space Administration

PEN Polyethylene Naphthalate

PET Polyethylene Terephthalate

SEM Scanning Electron Microscopy

TD Transverse Direction

TMA Thermomechanical Analyzer

UV Ultraviolet

UV-VIS-IR Ultraviolet-Visible-Infrared

1. Introduction

Solar sails are attractive spacecraft propulsion systems that offer extended mission capability 

by deriving thrust directly from momentum transfer of solar photons, rather than onboard fuel [1-

2]. The transferred photon momentum is very small but the acceleration can be maximized by 

increasing the surface area of the sail. For long duration missions, the sail material needs to survive 

temperature fluctuations, ultraviolet (UV) rays, ionizing radiation, ultrahigh vacuum, and 

micrometeoroid impacts [3-7]. Since the degradation of the sail material controls the operational 

lifetime, understanding the effects of the space environment on the sail membrane is essential for 

mission success. 

There have been several studies of space environment effects on candidate sail materials such 

as aluminized Mylar® (polyethylene terephthalate, PET), Teonex® (polyethylene naphthalate, 

PEN), CP1TM (colorless polyimide) and Kapton® polyimide [5-7]. After exposure of high energy 

electrons, protons and UV rays, the degradation of physical properties of sail materials was 

determined. However, there is no systematic study to investigate the chemical changes induced in 

the polymer under simulated space environment exposure. 

In this study, we simulated the effect of the space environment of ionizing radiation, thermal 

aging, and impact damage on mechanical, thermal, and optical properties of a commercial off the 

shelf (COTS) polyester membrane to assess the degradation mechanisms on a feasible solar sail. 

A quantitative study of space environment effects on the solar sail can provide design guidelines 

to increase the reliability of solar sails, resulting in increased acceptance of this type of propulsion 

system.

2. Experimental 

2.1. Materials 

PEN (Figure 1) as a sail core membrane was purchased from Dupont Teijin (Teonex® Q72, 

2μm thick). Metallized PEN was prepared by deposition of aluminum (1000Å) on the front side 

2
3 

of the membrane as a reflective layer and chromium (150Å) on the back side of the membrane as 

a thermal emitter, respectively (Astral Technology Unlimited, Inc.).

2.2. Electron Irradiation Tests 

Electron irradiation tests were performed by the Space Environmental group at NASA 

Marshall Space Flight Center (MSFC). The metallized PEN film was exposed to electron radiation 

for nineteen days with a fluence of 1.04x1017 electrons/cm2

. The electron beam energy and current 

were 70keV and 10 nA/cm2, respectively. The total exposure dosage was approximately 8.3 Grad. 

A Hitachi S-5000 high-resolution scanning electron microscope (HRSEM), with a field emission 

electron gun and in-lens detector, was used to examine the surface morphology of the metallized 

PEN film. Infrared (IR) spectra were taken in transmission mode with a Fourier Transform Infrared 

(FT-IR) spectrometer (Nicolet iSTM 5). 

2.3. Thermal Analysis 

Viscoelastic behavior of the metallized PEN film was characterized from storage and loss 

modulus at a heating rate of 1°C/min and 1 Hz in a dynamic mechanical analyzer (DMA Q800, 

TA Instruments). Thermal properties of melting, crystalline, and glass transition temperature of 

the metallized PEN film were characterized at a heating rate of 3°C/min with a modulation of 

±0.47°C for every 60 seconds using a modulated differential scanning calorimeter (MDSC, Q2000, 

TA Instruments). Coefficient of thermal expansion (CTE) was determined from the dimension 

change at a heating rate of 5°C/min in a thermomechanical analyzer (TMA, model 202, Netzsch). 

2.4. Thermal Aging Tests 

The metallized PEN film was exposed to elevated temperatures, and the mechanical and optical 

properties were measured. The films were affixed to glass slides to prepare for treatment at 

temperatures ranging from 75 to 275°C. The specimens were placed in a nitrogen purged 

convection oven (Blue M) and held at the treatment soak temperature for ten minutes. The treated 

specimens were examined under an optical microscope in reflectance and transmittance mode to 

examine cracking. Ultraviolet-visible-infrared (UV-VIS-IR) spectroscopy (PerkinElmer, Lambda 

1050 spectrometer) was performed in reflectance mode to determine the reflectivity from 250 to 

2400 nm at room temperature. 

2.5. Mechanical Property Tests 

Tensile properties of the PEN film were characterized according to American Society for 

Testing Materials (ASTM) Standard D882-12 [8]. Specimens (about 5 mm wide) were placed 

between grips with a gauge length of about 50 mm and tested at a rate of 5 mm/minute until failure. 

Mode I tearing tests were performed to calculate the essential work of fracture (EWF). Samples 

were prepared by cutting along two directions [machine direction (MD) and transverse direction 

(TD) of a film roll] to see the effect of cutting direction. Double-edge notched tension (DENT) 

3
4 

specimens 20 mm wide with 2, 4, 6, 8, and 10 mm ligament lengths were prepared using a 

straightedge and razor blade. The specimens were gripped with an initial gauge length of 40 mm 

and tested at a rate of 0.1 mm/minute until failure. The setup for this test is shown in Figure 2. 

Load-displacement graphs were generated, and the essential work of fracture calculated. 

Tear-propagation resistance in Mode III for the metallized PEN film was evaluated using 

ASTM Standard D1938-14 [9]. Trouser-shaped specimens 25 mm wide and 75 mm long with a 

vertical pre-crack of 50 mm were prepared using a straightedge and razor blade. The specimens 

were gripped at the two panels created by the crack with an initial grip separation of 50 mm. The 

top grip was extended at a rate of 250 mm/minute until the tear propagated through the entire 

length of the specimen, and load-displacement plots were generated. The setup for this test is 

shown in Figure 3. 

To simulate potential impact damage on the sail membrane, holes and slits were introduced 

before tensile testing of the metallized PEN film. Specimens 20 mm wide with a gauge length of 

100 mm were prepared. The pre-cracks of 2 mm width were made with a razor blade and a 2 mm 

diameter circular die (Figure 4). Tensile testing was performed with an extension rate of 5 

mm/minute and load-displacement graphs generated.

3. Results 

3.1. Electron Irradiation 

Figure 5 shows the appearance change of the metallized PEN film after electron irradiation of 

approximately 8.3 Grad. The irradiated films became wrinkled. This seemed to have originated 

from induced stress and thermal energy by the electron radiation. 

The surface morphology of the film was investigated by scanning electron microscopy (SEM) 

(Figure 6). Before irradiation, the film showed a smooth aluminum layer. However, after electron 

irradiation, the aluminum coating was damaged and delaminated exposing the PEN core layer 

underneath [Figure 6 (b)]. Even though the surface of aluminum coating was damaged, the solar 

absorbance of the aluminum side was unchanged (0.09 for control PEN film, and 0.09 for electron 

irradiated PEN film, Table 1). The thermal emittance of the aluminum side of the PEN film slightly 

increased from 0.05 for control PEN to 0.09 for irradiated PEN. 

Electron radiation exposure of the metallized PEN film led to a decrease in mechanical 

properties when compared to the control specimens, as shown in Figure 7 and Table 1. The change 

was obvious even before testing began because the samples were very brittle, and difficult to 

handle and set up for testing. The elastic modulus of the PEN was reduced from 8.43 GPa to 6.56 

GPa, and the exposed specimens broke near one percent elongation, indicating substantial 

embrittlement. The tensile strength was reduced from approximately 165 MPa to 46 MPa. The 

degradation of mechanical properties could be explained by chain scission and crosslinking of 

polymer molecules from the high energy electron radiation. 

The electron radiation induced molecular degradation was observed using various 

experimental techniques. Figure 8 shows storage and loss modulus of metallized PEN film as a 

function of temperature. The storage modulus of the control PEN film was about 5 − 9 GPa in the 

range of -60°C to 120°C. Above the glass transition (α-transition) of about 140°C, the storage 

4
5 

modulus decreased and was about 1.3 GPa just before crystalline melting (Tm) near 270°C. After 

electron irradiation, both the overall storage modulus and the glass transition decreased (from 

140°C to 137°C). The most interesting observation was the significant increase in a loss modulus 

at β*-transition, representing the out-of-plane motions of naphthalene rings or the fluctuation of 

aggregates of naphthalene rings [10]. The ratio of loss modulus of α-transition and β*-transition 

for the electron irradiated PEN film decreased to 0.62 from the 1.19 for the control PEN film, 

which indicates an increase in the short segmental mobility induced from chain scission of main 

polymer chains by the high energy radiation. 

The chain scission was also established from the differential scanning calorimetry (DSC) 

thermogram (Figure 9) and FT-IR spectra (Figure 10). The control PEN film shows a clear melting 

peak at about 260°C with the first heating run and a high crystallinity (χc) of about 54%, 

determined by 

 (1) (ܿ)௙ ⁄ ܪΔ) ݉௙(ܪΔ௖ = ߯

where Δܪ)௙݉ (is the measured heat of fusion of the semicrystalline PEN and Δܪ)௙ܿ (is the heat 

of fusion of 100% crystalline PEN (103J/g) [11]. With the second heating run, it showed a clear 

glass transition (at about 124°C), a crystalline peak (at about 190°C) and a Tm peak (at about 

260°C), in that order. On the contrary, the electron irradiated PEN film showed neither a clear 

glass transition nor a crystalline peak while showing a broad and small melting peak with the first 

heating run (χc of about 9%), which results from molecular chain degradation. 

Figure 10 shows the change of molecular structure of the metallized PEN film after electron 

irradiation. Compared to the peak for CH out of plane of aromatic moiety (760 cm-1), the peaks of 

=C-O (1240 cm-1), C-O-C (1178 cm-1), -O-C (1085 cm-1) and CH2 (1374, 1339 cm-1) of esters 

appear less intense, and apparent carboxylic acid characteristic peaks (the broad peak of -OH at 

about 3000 cm-1 and C=O at 1700 cm-1) begin to appear. This suggests that the PEN molecules 

were decomposed to some degree by the electron irradiation to yield carboxylic acid moieties 

(naphthanoic end groups). 

3.2. Thermal Aging Tests 

Thermal aging of metallized PEN film was examined. Figure 11 shows the coefficient of 

thermal expansion (CTE) of raw PEN film (without metal coatings) and metallized PEN film as a 

function of temperature. The CTE of the samples varied from about 9 to 13 ppm/°C for the range 

of 0 ~ 100°C. While the raw PEN films showed a large increase in CTE above the glass transition 

temperature (around 124°C), the metallized PEN films maintained a low CTE until reaching the 

melting temperature (about 260°C) because the metallic layers can restrict the macroscopic 

dimensional change of PEN film. This indicates that the operational limit of the metallized PEN 

film is more a function of the melting temperature, than the glass transition temperature. 

The change in appearance of the metallized PEN films after thermal treatment at various 

temperatures are shown in Figure 12. The PEN films were dimensionally stable up to about 150°C. 

5
6 

Above 150°C, there was some noticeable shrinkage below the melting temperature (around 

260°C). The sample at 300°C, [Figure 12. (h)] resulted in a significant degree of distortion. Cracks 

on the surfaces were observed by optical microscopy. 

Figure 13 shows spectral reflectance of metallized PEN films after thermal aging. The 

thermally aged metallized PEN films did not exhibit any significant change in reflectance, while 

the sample treated at 300°C showed a slight decrease in reflectance resulting from thermal 

distortion leading to surface cracks. 

The mechanical properties of metallized PEN films after thermal treatment are shown in Figure 

14. The Young’s modulus and tensile strength of thermally aged samples decreased slightly, while 

the elongation at the break of the sample treated at 225°C showed significant reduction. This would 

indicate that the metallized PEN sustains stable mechanical properties after thermal aging up to 

about 200°C. 

3.3. Simulated Impact Damage Effects on Mechanical Properties 

The primary cause of concern from micrometeoroids is physical damage upon impact. Erosion 

of surface materials can change spectral reflectance of sail membrane [3]. Even catastrophic failure 

can result from strain propagated tearing resulting from impact damage. Thus, tearing properties 

of a sail membrane as a function of damage geometry should be studied. Mode I tearing fracture 

of metallized PEN film was examined using the EWF method to separate the essential work to 

fracture the polymer (we) from the non-essential geometry-dependent work from plastic 

deformation (wp) using 

 (2) ܮ ௣ݓߚ + ௘ݓ = ௙ݓ

where wf is the specific total work of fracture, β is proportionality constant (plastic zone shape 

factor) whose value depends on the geometry of the specimen and the crack and L is ligament 

length [12-13]. 

Tensile tests of the DENT specimens with various ligament lengths (Figure 2) were plotted in 

Figure 15 (a). The load-extension plot shows that the maximum load and extension before failure 

decreases as the ligament length decreases, while the shape of the plots for varying ligament 

lengths remains the same. From the load-extension graph, the total work of fracture was calculated 

to obtain the we and β [Figure 15 (b) and Table 2]. The we of metallized PEN films were 23.8 and 

27.3 kJ/m2

 for MD and TD, respectively. These measured values are lower than the literature stated 

range of 55 – 75 kJ/m2, probably because the metallized PEN was manufactured by bi-axially 

stretching to induce high crystallinity (over 50%). Also, the bubbles in the film, which were 

discovered using microscopy, can lower fracture toughness. β, which represents geometry related 

plastic zone factor was also less than the literature value (5 – 23 MJ/m3

). 

Mode III tearing fracture toughness was measured by a trouser tear test (Figure 3). The trouser 

tear specimen was gripped at the two panels created by the pre-crack and the load was recorded 

with crack propagation induced by the extension of the grip distance. An approximate load of 1.5 

mN for the metallized PEN was required for the pre-crack to propagate, which shows that the 

6
7 

material can fail catastrophically under a light load if an edge crack is present. Tearing energy and 

work are summarized in Table 2. 

To investigate the impact damage on the mechanical properties, holes and slits were introduced 

into the membrane. Metallized PEN films with pre-cracks from a die (2 mm diameter die hole) 

and blade cuts (2 mm wide slit) failed at a lower load and elongation than control specimens. The 

2 mm diameter die cut specimens failed at a tensile stress and strain of approximately 130 MPa 

and 2.5%. The specimens with a 2 mm wide slit failed at approximately 60 MPa and 1% 

elongation. Even though the pre-damage was introduced, the induced tensile stress is higher than 

the biaxial tension level of deployed solar sails [about 0.007 MPa (about 1 psi)] [14]. 

4. Conclusions 

The effects of select simulated space environments on mechanical, thermal and optical 

properties of a COTS polyester, metallized PEN solar sail membrane were investigated by electron 

irradiation, thermal aging and simulated impact damage tests. After a 8.3 Grad dose of electron 

irradiation, the tensile modulus, tensile strength and failure strain of metallized PEN film decreased 

by 20% to 95%. However, the membrane did not show any significant change in optical properties 

of solar absorbance and thermal emittance of the reflective side (aluminum layer). By thermal and 

spectroscopic analysis, polymer molecular degradation under electron irradiation was confirmed. 

Based on thermal aging testing, it is speculated that the operational temperature limit of a 

metallized PEN sail can be assumed to approach the melting temperature of PEN, with the 

elongation result from the thermal aging being a better predictor. The pre-cracked specimens that 

simulate potential impact damage exhibited significant degradation in tensile strength. Further 

quantitative studies of space environment effects such as proton, UV radiation or combined 

radiation on the solar sail membrane can provide design guidelines that will increase the reliability 

of solar sails. 

Acknowledgments 

Authors acknowledge Drs. Sheila Thibeault and D. Laurence Thomsen III for their valuable 

comments on radiation effects, and Mr. Harold Claytor, Mr. Joel Alexa and Ms. Crystal 

Chamberlain for their help in experimental preparation. 

 

7
8 

References 

1. Wilkie, W. K., Warren, J. E., Thompson, M. W., Lisman, P. D., Walkemeyer, P. E., 

Guerrant, D. V. and Lawrence, D. A.: The Heliogyro Reloaded, Joint Army-Navy-NASAAir Force (JANNAF) Interagency Propulsion Committee Meeting, Huntsville, AL, USA, 

December 5-9, 2011. 

2. Mcinnes, C. R.: Solar Sailing: Technology, Dynamics and Mission Application, Springer 

Praxis, New York, 1999. 

3. Tribble, A. C.: The Space Environment: Implications for Spacecraft Design, Princeton 

University Press, New Jersey, 2003. 

4. Bryant, R. G., Seaman, S. T., Wilkie, W. K., Miyauchi, M. and Working, D. C.: Selection 

and Manufacturing of Membrane Materials for Solar Sails, Advances in Solar Sailing, 

Macdonald, M. (ed.).; Springer Berlin Heidelberg, 2014; pp 525-540. 

5. Edwards, D. L., Semmel, C., Hovater, M., Nehls, M., Gray, P. Hubbs, W. and Werts, G.: 

Solar Sail Material Performance Property Response to Space Environmental Effects, 

Proceedings of SPIE, Vol 5554, SPIE, Bellingham, WA, 2004. 

6. Edwards, D. L., Hubbs, W. S., Wertz, G. E., Hoppe, D. T., Nehls, M. K., Hollerman,W. A., 

Gray, P. A. and Semmel, C. L.: Electron Radiation Effects on Candidate Solar Sail Material, 

High Performance Polymers, 16 (2003), pp.277-288. 

7. Hollerman, W., Bergeron, N. P. and Moore, R. J.: Proton Survivability Measurements for 

Candidate Solar Sail Materials, IEEE Nuclear Science Symposium Conference Record, 

2005, pp. 1436-1440. 

8. ASTM Standard D882-12, “Standard Test Method for Tensile Properties of Thin Plastic 

Sheeting.” 

9. ASTM Standard D1938-14, “Standard Test Method for Tear-Propagation Resistance of 

Plastic Film and Thin Sheeting by a Single-Tear Method.” 

10. Hardy, L., Stevenson, I., Fritz, A., Boiteux, G., Seytre, G. and Schönhals, A.: Dielectric 

and Dynamic Mechanical Relaxation Behavior of Poly(ethylene 2,6-naphthalate 

dicarboxylate). II. Semicrystalline Oriented Films, Polymer, 44 (2003), pp. 4311-4323. 

11. Wunderlich, B. and Cheng, S. Z. D.: Glass Transition and Melting Behavior of 

Poly(ethylene-2,6-naphthalenedicarboxylate), Macromolecules, 21 (1988), pp. 789-797. 

12. Bárány, T., Czigány, T. and Karger-Kocsis, J. Application of the Essential Work of 

Fracture (EWF) Concept for Polymers, Related Blends and Composites: A Review, 

Progress in Polymer Science, 35 (2010), pp. 1257-1287. 

13. Arkhireyeva, S. and Hashemi, S.: Fracture Behaviour of Polyethylene naphthalate (PEN), 

Polymer, 43 (2002), pp.289-300. 

14. Greschik, G. and Mikulas, M. M.: Design Study of a Square Solar Sail Architecture, 

Journal of Spacecraft and Rockets, 39 (2002), pp. 653-661. 

8
9 

Table 1. Physical properties of the metallized PEN. 

Metalized 

Film Modulus (GPa) Tensile Strength 

(MPa) 

Elongation at 

Break (%) 

Solar 

Absorbance 

Thermal 

Emittance 

Control PEN 8.43 ± 0.14 164.89 ± 5.35 18.20 ± 5.97 0.09 0.05 

Electron 

Irradiated 

PEN 

6.56 ± 0.23 46.42 ± 25.09 0.76 ± 0.44 0.09 0.09 

Table 2. Tear physical properties of the metallized PEN. 

Material 

Mode I Tear Fracture Mode III Tear Fracture 

Essential Work 

of Fracture, we

(kJ/m2

) 

Shape Factor, 

β (kJ/m3) Tearing Energy (N/m) Tearing Work 

(N⋅m) 

Metallized 

PEN 

1

MD 23.8 ± 1.5 1.1 ± 0.2 1361.0 ± 58.9 72.0 ± 3.1 

2

TD 27.3 ± 1.4 0.9 ± 0.2 1517.4 ± 179.2 80.2 ± 9.5 

1

MD: Machine Direction 

2

TD: Transverse Direction 

 

9
10 

 

Figure 1. Molecular structure of PEN. 

Figure 2. (a) Sample preparation and (b) setup during testing for DENT 

configuration (Mode I tear test). 

(a) (b)

10
11 

 

Figure 3. (a) Sample configuration and (b) setup during testing for Mode III 

tear-propagation resistance. 

Figure 4. Setup for tensile test of metallized PEN films with a 2 mm die-cut 

hole to simulate potential impact damage. 

(a) (b) 

1 in (25.4 mm) 

2 in (50.8 mm) 

 3 in (76.2 mm) 

11
12 

 

Figure 5. Metallized PEN films on the sample holder plate (a) before electron 

irradiation and (b) after electron irradiation. 

(a) (b) 

Figure 6. SEM image of the aluminum coating surface of the metallized PEN 

films (a) before electron irradiation and (b) after electron irradiation. 

(a) (b) 

Al layer 

PEN

12
13 

Figure 7. Tensile properties of metalized (a) control PEN and (b) electron 

irradiated PEN films. Each color represents one of 5 tensile test specimens. 

(a) 

(b) 

13
14 

 

Figure 8. DMA curves of control and electron irradiated PEN films. 

Figure 9. DSC thermograms of control and electron irradiated PEN films. 

14
15 

 

Figure 10. FT-IR spectra of (a) control and (b) electron irradiated PEN films. 

(a) 

(b) 

O-H 

C=O 

C-H 

=C-O 

C-O-C 

O-C 

C-H 

15
16 

 

Figure 11. CTE of raw PEN films and metallized PEN films. 

16
17 

 

Figure 12. Appearance of metallized PEN films after thermal aging test at (a) room 

temperature, (b) 100°C, (c) 125°C, (d) 150°C, (e) 175°C, (f) 200°C, (g) 225°C and 

(h) 300°C. 

(a) 

(c) 

(e) 

(g) 

(b) 

(d) 

(f) 

(h) 

RT 100°C 

125°C 150°C 

175°C 200°C 

225°C 300°C 

17
18 

 

Figure 13. Spectra reflectance of metallized PEN films after thermal aging at various 

temperatures from RT to 300°C.

Figure 14. Mechanical properties of metallized PEN films after thermal aging at 

various temperatures of room temperature (control), 200 and 225°C. 

18
19 

 

Figure 15. Mode I tear fracture properties of metallized PEN films. (a) Load vs. 

displacement profile and (b) specific total work of fracture (wf) vs. ligament length 

(L). 

(a) 

(b) 

2mm 

10mm 

19
20 

Figure 16. Tensile properties of metallized PEN films with simulated impact 

damage. 

20
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U U U UU

Degradation; Membrane; Radiation; Solar sail; Space environment

 

 Simulated Space Environmental Effects on Candidate Solar Sail Material 

Kang, Jin Ho; Bryant, Robert G.; Wilkie, William K.; Wadsworth, Heather M.; 

Craven, Paul D.; Nehls, Mary K.; Vaughn, Jason A.

 

28

NASA

432938.08.01.07.01 

For long duration missions of solar sails, the sail material needs to survive harsh space environments and the degradation of the sail material controls operational lifetime. 

Therefore, understanding the effects of the space environment on the sail membrane is essential for mission success. In this study, we investigated the effect of simulated 

space environments of ionizing radiation and thermal aging. Simulated potential damage effects on the mechanical, thermal and optical properties of a commercial off the 

shelf (COTS) polyester solar sail membrane to assess the degradation mechanisms on a feasible solar sail. The solar sail membrane was exposed to high energy electrons 

(about 70 keV and 10 nA/cm2), and the physical properties were characterized. After about 8.3 Grad dose, the tensile modulus, tensile strength and failure strain of the sail 

membrane decreased by 20 to 95%. The aluminum reflective layer was damaged and partially delaminated but it did not show any significant change in solar absorbance or 

thermal emittance. The mechanical properties of a pre-cracked sample, simulating potential impact damage of the sail membrane, as well as thermal aging effects on 

metallized PEN (polyethylene naphthalate) film, will be discussed.