How to Evaluate Your Hardcoated Polycarbonate for Ballistic Performance

How to Evaluate Your Hardcoated Polycarbonate for Ballistic Performance
The following information is provided by Close Focus Research (CFR) to aid glazing developers on how to evaluate Hardcoated Polycarbonate materials if they are to be used as the rear face plys in Ballistic Resistant Glazings.

If your Glass / Polycarbonate Glazing product is going to be tested, or it has already been tested for Ballistic Resistance, and you expect or notice that the height of the individual projectile bulges in the hardcoated polycarbonate rear face ply is greater than 0.375 inches, then you should take note of the following information.

     

In many cases, the Hardcoat chemical solution applied to the polycarbonate surface to enhance its scratch resistance can make ploycarbonate brittle, thus reducing its overall plasticity. When Hardcoated polycarbonate is used as the rear face ply in a Ballistic Resistant Glazing, one should be aware that a glass / polycarbonate product may pass a ballistic test when using polycarbonate material supplied from one vendor and may fail when using polycarbonate material supplied from another vendor.

If you plan on utilizing Hardcoated Polycarbonate in your glazing designs, then you need to develop a Hardcoated Polycarbonate Evaluation program. This way you can determine which Hardcoated Polycarbonate brands will be acceptable for Ballistic performance and ensure that the ballistic performance of your products will remain consistent.

There are two methods you can use to determine the plasticity of different Hardcoated Polycarbonate brands. The first method utilizes a dart-drop in which a blunt-nosed dart is dropped onto a sheet of Hardcoated Polycarbonate. The second method is an in-house ballistic test. With either test method, you want to determine the plasticity of the Hardcoated Polycarbonate by observing the resulting bulge height in the polycarbonate. In some cases the material will bulge and in others, the material will crack. What you want to avoid is material that cracks and will not deform properly.

The following Glass / Polycarbonate cross sections can be used as material test reference designs for evaluating different brands of Hardcoated Polycarbonate for Ballistic Performance. These two designs will yield large projectile bulges in the Hardcoated Polycarbonate rear face ply when shot with single round from a 7.62 x 39 mm rifle. If the Hardcoated Polycarbonate rear face ply cracks under these test condition, then you can reject the material as being too brittle for use in Ballistic Resistant Glazings.

It is highly recommended that you come up with your own ballistic cross-section evaluation design that will yield similar results using a 30-06 round fired at approximately 2800 ft /sec. It is very important that you determine the plasticity of your Hardcoated Polycarbonate materials before you incorporate them into any ballistic resistant design.

Glazing Designs for Evaluating the Ballistic Performance of Hardcoated Polycarbonate Test Weapon / Cartridge: 7.62 X 39 mm, 123 grain FMJ, Median Velocity = 2310 ft / sec Sample Size = 12 x 12 inch
Ballistic Test Results: 1 inch High Bulge in the Polycarbonate Rear Face Ply
3/16 inch Hardcoated Polycarbonate Design 0.125 inch  Annealed Glass 0.060 inch  PVB Interlayer 0.375 inch  Annealed Glass 0.050 inch  Urethane Interlayer 0.188 inch  Hardcoated Polycarbonate 0.798 inch  Total Nominal Thickness
Ballistic Test Results: 5/8 inch High Bulge in the Polycarbonate Rear Face Ply
1/4 inch Hardcoated Polycarbonate Design 0.125 inch  Annealed Glass 0.060 inch  PVB Interlayer 0.375 inch  Annealed Glass 0.050 inch  Urethane Interlayer 0.250 inch  Hardcoated Polycarbonate 0.860 inch  Total Nominal Thickness

Developing Glass / Polycarbonate Glazings for Extreme Cold Weather
If you plan on utilizing any Glass / Polycarbonate Glazing products in extreme cold weather, Close Focus Research (CFR) recommended that you either replace all the PVB interlayers with either urethane or a high-grade aerospace grade PVB. Architectural PVB tends to become brittle as the temperature drops and can fail when utilized in a product that is subjected to extreme code weather.