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Transparent Protective Window Systems
SAFirE™ Transparent Protection Solutions address the ever-increasing demands of high-velocity (kinetic energy) projectile protective performance at a reduced weight and thickness. Results from our latest designs have shown a greater than 50% reduction in weight and thickness at improved kinetic energy protective performance compared to traditional glass solutions. Alternatively, performance can be significantly enhanced without increasing weight and thickness. Sapphire is superior over ALON® and Spinel in optical and stopping power protective performance and is immediately available for high volume, large aperture platforms.
Our transparent protective product line incorporates EFG™ Sapphire, the hardest transparent material 2nd only to diamond, which provides an extremely hard and abrasion-resistant strike face that ‘breaks’ the projectile upon impact. SAFirE™ solutions have been designed to meet a variety of threats while providing improved situational awareness in both the visual and Infra-Red spectra. SAFirE™ is currently being used in both ground vehicle and rotary-wing platforms.
Choosing the proper material depends on forces experienced by the part, required wavelength range of the optics, overall weight envelope of the platform, and other design constraints.
Uses/Applications
- Ground vehicles
- Rotary wing aircraft
- Protective shields
- Personal protection
- Building / facility security
Features/Benefits
- >50% reduction in weight & thickness
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Significant abrasion resistance
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Improved night vision transmittance
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Reduced risk of delamination
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‘Breaks’ the projectile
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Chemically inert
Standard available sheet product features include:
- Unpolished, “As Grown”, thickness from .060” to .500” (1.5 to 12.7 mm)
- Polished thickness from .030” to .35” (0.76 to 8.9 mm)
- Widths to 12.0” (304 mm), Lengths to 81.0” (2057 mm)
- Disk diameters 0.125” to 12.0” (3.1 to 304 mm)
- Standard available tube sizes range from .06” to 1.7” (1.5 mm to 43.0 mm) outside diameter
- Standard available rod sizes up to .30” (7.6 mm) diameter and 40.0” (1016 mm) length
Material Comparison to Saint-Gobain Synthetic Sapphire Window |
||||||||
|---|---|---|---|---|---|---|---|---|
| Transparency Type | Material |
Density g/cc |
Areal Density psf/in |
Young's Modulus Gpa |
Knoop Hardness Kg/mm2 |
Fracture Toughness MPa-m1/2 |
Thermal Conductivity W/m-K |
Thermal Expansion 10-7/K |
| Glass | Soda-Lime Glass | 2.52 | 13.1 | 69.6 | 585 | 0.75 | 0.9 - 1.3 | 90 |
| Glass-Ceramic | Li-Alumino-Silicate | 2.52 | 13.1 | 88.5 | 570 | 1.1 | 1.6 - 1.3 | 0 |
| Ceramic | ALON® | 3.69 | 19.2 | 323 | 1850 | 2 | 9.6 | 56 |
| Spinel | 3.58 | 18.6 | 277 | 1645 | 1.5 - 2 | 14.7 | 60 | |
| Sapphire | 3.9 | 20.2 | 435 | 2000 | 2 | 32 | 60 | |
| Metal | Armor Steel | 7.9 | 40.8 | 210 | 340 | 7 | 40 - 60 | 115 |
Note: Armor steel (opaque) is included as a reference only
Physical/Mechanical
| Properties | Value |
|---|---|
| Density | 3.97 gm/cm3 (0.143 lb/in3) (25°C) |
| Young’s Modulus | 435 GPa (63 x 106 psi) parallel to C-axis (25°C) 386 GPa (56 x 106 psi) parallel to C-axis (1000°C) |
| Modulus of Rigidity (Shear Modulus) | 175 GPa (26 x 106 psi) |
| Flexural Strength | 1035 MPa (150 kpsi) parallel to C-axis (25°) 760 MPa (110 kpsi) perpendicular to C-axis (25°) |
| Compressive Strength | ≈2 GPa (300 kpsi) (25°) |
| Hardness |
9 Mohs scale (between 20° and 25°C) 1900 Knoop parallel to C-axis |
Optical
| Properties | Value |
|---|---|
| Transmission | UV through midwave IR (~200-5000nm) |
| Uniaxial Negative Refractive Index | Ordinary ray (C-axis) No = 1.768 Extraordinary ray Ne-1.760 Birefringence: 0.008 |
| Temperature Coefficient of Refractive Index | 13 X 10-6/°C (visible range) |
| Spectral Emittance | 0.1 (1600°C) |
| Spectral Absorption | 0.1 – 0.2cm-1 (0.66 μm, 1600°C) |
Thermal
| Properties | Value |
|---|---|
| Melting Point | 2053°C (3727°F) |
| Specific Heat | 0.181 cal/gm°K (25°C) 0.300 cal/gm°K (1000°C) |
| Thermal Conductivity | 0.4 watts/cm°K (25°C) 0.1 watts/cm°K (1000°C) |
| Thermal Expansion Coefficient | (25 – 1000°C) 8.8 x 10-6; parallel to C-axis 7.9 x 10-6; perpendicular to C-axis |