Question:
Can bulletproof glass break if it is shot enough times with an AK-47 firing 7.62mm rounds?
Answers:
Nothing is OFFICIALLY called bulletproof. That is a euphemism that the media and those who don't know any better perpetuate. The official term is "bullet-resistant", which more closely describes the true nature of things.
What people normally call bulletproof glass is actually a glass/polycarbonate (a high strength plastic, similar to that used in airplane windows) laminate. When struck, the glass layers do shatter, but they are contained by the polycarbonate, thereby preventing the entire window from shattering and dissipating the energy from the bullet. If enough bullets hit in a compromised area or have more energy than the glass can dissipate, they will punch through. For example, glass rated as resistant to 7.62mm AK-47 rounds will not stop a 50 caliber round.
A bulletproof vest works much the same way, absorbing and dissipating the majority of the bullet's energy, rather than diflecting it.
Glass has been used as a flooring product for more than 100 years. Often found in historic buildings, it was typically a molten cast product of varying thicknesses. Today, glass flooring and stair treads, usually installed by glazing contractors, are in high demand. Since glass can be utilized safely in flooring applications, it is being specified at an amazing pace. It can now be found in restaurants, galleries, libraries, corporate offices, retail businesses and private residences around the world.
The use of glass flooring has accelerated for a number of reasons. One reason is because it provides daylighting. Daylighting occurs when natural light filters into areas that would have to be lit typically with artificial light. Glass flooring allows natural light to brighten the area without the need for artificial light.
Another reason for choosing glass flooring is the dramatic ambiance it can provide. Many designs call for fully-exposed, monolithically polished glass edges and structural support systems that appear to allow the glass to float in place. This provides a level of elegance that cannot be found in other flooring products.The Elements
Glass flooring is made of mutli-layer, laminated panels, and no two glass flooring projects are alike. The number of glass lites per panel and overall thickness varies from project to project; there is no such thing as a standard make-up or thickness that will work in every situation. Structural support is also important when working with glass flooring because it dictates the final glass make-up.
The top layer of glass flooring should include an anti-slip surface. Many anti-slip design options are available, including sandblasted, acid-etched, cast, ceramic frit and silk-screened glass. Play it Safe
Whatever top surface effect used, surfaces need to be tested properly for slip resistance. Many in the construction industry recognize Underwriters Laboratories (UL) as a trusted source for product compliance. UL 410 is the standard for slip resistance of floor surface materials.
A monolithically polished edge on stair treads is a highly requested treatment. With such an edge, a fully laminated panel, rather than individual lites, is polished prior to laminating. Monolithically polished edges provide a high level of quality and allow for a less blunt edge on the glass treads so there is less opportunity for breakage.
Manufacturers currently offer fully annealed glass panels, fully tempered panels or a combination of annealed and tempered in their flooring solutions. The use of fully annealed panels in flooring applications could result in serious safety concerns for patrons. For example, in the event of a panel failure, a fully annealed panel is likely to have a consistent break pattern between all annealed lites and, in turn, not hold a person’s weight. In other words, an individual could fall through the glass and/or sustain serious injuries. A fully tempered laminated panel, however, has been proven in testing to be strong and safe.Privacy, PleaseMany public locations require a privacy-type glass to ensure an individual’s modesty. Other projects require a totally transparent glass so that video or artwork can be seen below while walking on top of the glass. The top, anti-slip layer of glass or the bottom layer of glass provides these options, which can be a cast panel of glass, acid-etched layer or a sandblasted, clear tempered panel.
Adding color is yet another option for glass flooring. This can be achieved through solid colored glass, colored laminated interlayers or via painting. With manufactured colored glass, color is an inherent part of the glass. This type works well with a fully exposed edge and when a solid, consistent color is desired for the entire panel. Interlayers can be used to tint the glass panel to the desired color when exposed edges are not involved. With painted glass, numerous custom effects/designs can be achieved, and the number of colors available is unlimited.Safety Assured
As the popularity of glass flooring has grown, some manufacturers have begun to offer glass-flooring products that are not tested or engineered properly. Using such products could pose potential liability issues. Along with a UL-tested and approved top surface, the glass and the structural support system for the project should be engineered properly. A tested product, a manufacturer employing a structural glass engineer (different than a regular structural engineer) and with glass flooring experience can make the entire process smooth and safe for everyone.
Why use laminated glass?
Explore these "Top 10" benefits:
In home construction or in other building projects, the benefits of using laminated glass include:
• Safety
• Security
• Sound Reduction
• Solar Energy Control
• UV Control
• Weather/Natural Disasters
• Durability
• Design Versatility
• Installation Ease
• Low Visible Distortion
Safety
Ordinary window glass is brittle, breaking into long sharp pieces which can cause serious and sometimes fatal injuries. The principal feature of laminated safety glass is its performance under
impact. We interlayers absorb the energy of the impact, resisting penetration. Although the
glass may break, the glass fragments remain firmly bonded to the interlayer, minimizing the risk of injuries. Little wonder that laminated glass is mandatory for automotive windshields in almost every industrialized country in the world and increasingly specified or required in architectural glazing.
In glass skylights, sunspaces, sloped glazing installations and curtainwalls, there is always the possibility of glass breakage. Without laminated glass, that could mean a big safety problem caused by falling glass. Unlike all types of monolithic glass, laminated glass remains intact when broken, protecting people from injury. This is why many building codes worldwide require laminated glass
for overhead glazing.
Security
Burglars often break windows to get to door and window handles, and laminated glass can resist their intrusion. Even if it is accidentally broken, the interlayer continues to safeguard the building until the glass is replaced. Reglazing can be done when convenient, rather than during expensive after-hours.
Laminated glass can be designed to withstand bullets and bomb blasts by using multiple or thick layers of glass and interlayer. In prisons, laminated security glass can replace traditional bars to create a more humane environment.
The rise in urban crime and terrorism has created a need for glazing materials that enable people to carry on normally and be protected from harm. Laminated glass made up of several glass sheets
and interlayers can provide protection in medium to high security applications. For extra security,
including uparmoring of vehicles, AJJ Glass offers DuPont SentryGlas® Plus interlayers with 100 times the stiffness and 5 times the toughness of traditional interlayers.
Sound reduction
Noise, just like a burglar, gains easiest entry to homes and buildings through windows. Laminated glass has proven to be an excellent barrier to noise, having a higher sound reduction index than
monolithic glass of equal thickness between the frequencies of 125Hz and 4,000Hz. This sound
dampening is due to the "viscoelastic" properties of the interlayer material. The coincidence effect experienced with monolithic glass at certain frequencies is also considerably reduced with laminated glass, and the noise reduction performance of IG units can be greatly improved by incorporating at least one layer of laminated glass.
Tailored for noise control applications, DuPont™ SentryGlas® Acoustic™ sound reduction interlayers
are available.
Solar energy control
While natural light plays an important role in architectural design, too much sunlight can also mean too much heat. Tinted laminated glass can reduce heat gain from sunlight to lower air conditioning costs, and it can also control glare.
Laminated glass also can be used to combine reflective coated glass or low-E glass with heat- absorbing glass tints. In warm climates, these combine the penetration resistance and sound reducing qualities of laminated glass with good shading and energy management. In laminated
glass containing coated glass, the metallic coating faces toward the inside of the laminate, where it
is protected from harmful dirt or contact.
UV control
The major cause of deterioration and fading of furnishings and pictures is the chemical reaction caused by short-wavelength UV radiation. UV-absorbing additives in the interlayer in laminated glass can screen out almost all these damaging rays.
Protection from weather and natural disasters
If broken, laminated glass remains in its frame, preventing interior damage, while reduced flying glass protects people both indoors and outdoors.
In developed areas subject to heavy winds and rains such as hurricanes or cyclones, buildings often need extra protection. Flying debris carried by these winds can shatter the glass of windows and doors, injuring people and opening buildings to often devastating further damage. Laminated glass constructions can be properly designed to remain intact under impact and keep the envelope of the home or building sealed.
Glass fallout in earthquakes exposes people to dangerous broken shards. Again, laminated glass has been shown to keep the glass intact and in its frame.
Durability
Laminated glass is durable, maintaining its color and strength, and is as easily cleaned as ordinary glass.
Design versatility
Laminated glazings can be manufactured flat or curved, and include annealed, toughened, heat- strengthened, spandrel, wired, patterned, tinted and reflective glasses. DuPont glass laminating interlayers can be used to add color tints or increase the opacity of the glazing, for further design aesthetics or privacy needs.
For even more design freedom, DuPont™ SentryGlas® Expressions™ offers decorative interlayers in
a range of transparencies. High-resolution digital printing adds custom color effects, words, patterns
or images - anything you imagine - to the interlayer prior to lamination. Located inside the glass, your design is beyond the reach of stains, fingerprints, abrasions or harsh cleaning chemicals. The result is a durable, easy-to-maintain, "signature" or branded environment with the full safety performance of conventional laminated glass.
Installation ease
Laminated glass is simple to install. Standard-sized, two-ply glass panels can be cut to size on-site, and can also be drilled or notched.
Low visual distortion
Laminated building glass is usually glazed in an annealed form, avoiding the distortion caused by
"roller waves" in tempered and heat-strengthened glass. Sharp reflected images are possible with curtainwalls constructed of laminated annealed glass.
