Technologies

Transparent materials
Heating systems
Systems
Typical designs

Transparent materials

Structural materials

GLASS
Glass is a very attractive material in transparency design because of its unequalled properties of durability. It can be reinforced up to considerable strength by making its surfaces permanently compressed. Therefore, Saint-Gobain Sully has successfully developed glass strengthening processes (thermal tempering and chemical reinforcement) which tremendously increase glass strength-to-weight ratio.
Thermal tempering is extensively employed. The surface compression, hence the reinforcement, remains limited in comparison with those possibly obtained from chemical processing, especially if a good optical quality has to be provided.
Chemical reinforcement provides glass with exceptional strength and superior optical quality. Basically, a graft of larger ions into the solid structure of the superficial layers makes them highly compressed. Saint-Gobain Sully has developed SOLIDION®, a glass of a new patented composition featuring the best properties among all available glasses on the market, a high modulus of rupture as well as a remarkable damage tolerance. There is no limitation in shape or thickness and all glasses, even the thinnest, can be efficiently reinforced while the optical quality is preserved.

ACRYLIC
Thermoplastic polymers, acrylic materials have found large applications in aircraft and helicopters since they allow to manufacture light, clear and complex shaped transparencies. As-cast acrylic is typically used for helicopters and non-pressurized aircraft transparencies.
Stretched acrylic is obtained by stretching as-cast acrylic sheets, a process which reorientates the long polymer chains. This drastically increases the material properties. ACRYLEX® stretched acrylic has been developed by Saint-Gobain Sully and shows an improved craze resistance as well as a far better stress, crack propagation and solvent resistance than as-cast acrylic. It is therefore suitable for birdproof windshields, canopies, outer cabin window panes and other transparencies for pressurized aircraft.

POLYCARBONATE
Polycarbonate features an exceptional toughness and impact resistance, making it a really attractive material in design of windshields submitted to high velocity birdstrikes. It is light and shows a good temperature resistance. Susceptible to stress-solvent crazing, polycarbonate has to be employed with a protective coating.

Interlayers

Interlayers are the transparent adhesives employed to bond the individual glass or plastic plies together. Interlayers provide a flexible medium to improve shatter and impact characteristics of transparencies. Electrical heating systems and temperature sensors are also embedded in the interlayers. In some configurations, because of their adhesion, tear resistance and ultimate tensile properties, the interlayers have membrane capabilities and the nominal aircraft pressurization can be, at least partially, retained in the occurrence of a complete glass failure.
For all these reasons, an adequate choice and construction of interlayers is crucial in transparency design.

VINYL
Plasticized polyvinyl butyral (PVB) used to be the most prevalent material for lamination of transparencies as it features excellent tear and tensile strengths. It offers a good mechanical coupling between plies and, as such, is suitable to laminate main plies together.

URETHANE
Polyurethane is intrinsically elastomeric and requires no plasticizer to provide flexibility. This is the reason for more constant properties over a wider range of temperature, comparatively to plasticized PVB. Therefore the trend for new glass window interlayer design consists in TPU layers to bond the face-plies and PVB layers to laminate the main plies together.

Heating systems

Saint-Gobain Sully has developed four high performance heating systems to de-fog and/or de-ice windshields under any weather conditions.

Conductive coatings

ELECTRIPLEX®
ELECTRIPLEX® is a tin oxide film applied by a pyrolytic method. As the deposition process requires a temperature near the glass softening point, this is accomplished in conjunction with tempering and is therefore applicable to thermally tempered glass only.
ELECTRIPLEX® had for long time heated Airbus A300/A310 and DC9/MD80 windshields.

INDIEX®
INDIEX® is an indium tin oxide coating, vacuum deposited. It is highly transparent and helps preventing delamination as the adhesion on glass and interlayers is stronger than for gold coatings. INDIEX® can be applied to any flat or curved glass, including chemically or thermally tempered.
INDIEX® currently heats AIRBUS A300/A310/A320/A330/A340, BOEING 737, DORNIER 328, ATR 42/72 and helicopters SUPER PUMA windshields.

ANTEX®
ANTEX® is a gold film, vacuum deposited. ANTEX® can be applied to any flat or curved acrylic or glass, including chemically or thermally tempered.
ANTEX® had for long time heated Agusta 129 windows and ACRYLOR® currently heats Transall C160 windows.

AIRPLEX® wire-grid system

AIRPLEX® is a conductive wire-grid embedded in the interlayer next to either acrylic or glass. It is made of nearly invisible resistance wires placed parallel in a sine wave form.
Saint-Gobain Sully's AIRPLEX® wire-grids are world-wide known for their sophisticated design and high quality. Largely used to heat all AIRBUS cockpit side-windows, AIRPLEX® currently powers the transparencies of the FALCON JETS, ATR42/72, CASA 212 and 235, TRANSALL C160, CORVETTE SN601, SAAB 340, BEECH KING AIR, SHORT 360 and helicopters SUPER PUMA, DAUPHIN and LYNX.

Systems

Anti static

As the external surface of a windshield makes an electrically insulated section in an aircraft fuselage, a static electric charging can take place during flight. To prevent uncontrolled discharges causing flashovers and face ply damages, an excellent protection can be provided by a conductive coating, grounded for a continuous draining of the static charges. Fairly resistant to degradation by erosion, abrasion effects of windshield wipers, cleaning and weather, it has a negligible effect (practically less than 5%) in the light transmission of windshields.

Anti solar

Like greenhouses, untreated transparency enclosures have the property to catch most of the energy from solar radiation, which causes their internal temperature to raise. Typically an ACRYLOR® gold film developed by Saint-Gobain Sully can reflect 50% of the incident energy with a light transmission as high as 70%. ACRYLOR® is currently employed on Mirage 2000, Rafale, Super-Puma VIP, Grob Egrett and Bell 609 transparencies.

Anti radar (EMI)

Glass and plastic transparencies allow microwave energy to enter aircraft cockpits, where flat metal surfaces become major sources of radar reflection back to the radar antenna. Making the transparencies reflective for radar beams considerably reduces the radar cross-section since, because of the transparency slopes, the incident microwaves are reflected to other directions. To get this shielding effect, Saint-Gobain Sully proposes conductive coating for transparencies.

Dry coat

DRY-COAT® is a highly hydrophobic film for glass that provides aircraft windshields with permanent rain-shedding properties to ensure a clear vision in all weather conditions. The chemical grafting of the film to the glass provides an abrasion resistance and a weatherability which are both good enough to permit DRY-COAT® to remain efficient for several months. At last, DRY-COAT® can be refurbished in-place in a very short time with no windshield removal.

Typical designs

Edge attachment

Edge attachment is a crucial point in designing aircraft transparencies as it is responsible for interchangeability, as well as for the pressure load transfer between the transparency and the airframe.

BOLTED ATTACHMENT
Stretched acrylic and polycarbonate laminated transparencies can have holes drilled directly through the main plies. When necessary, an edge reinforcement can provide greater fastener bearing area.

Glass transparencies need extended interlayer and special edge reinforcement for a bolted installation, since holes cannot be drilled through the glass plies.

CLAMPED ATTACHMENT
In comparison with a bolted design, the stress concentrations in the transparency due to the fasteners are eliminated, the edge support is more uniform and no in-plane loads are transmitted from the airframe. Also, the interchangeability is easier, because there is no need for matching the holes in the airframe with those of the transparency.

A clamped dry installation is recommended for glass transparencies, the entire edge of which can be encased in molded silicone rubber seals. Because any item of the same part-number has a seal molded from the same solid tool, a perfect interchangeability is obtained. The design of the seal includes nibs to be compressed at installation, thus providing an excellent air and water tightness.

Moisture sealing

Moisture ingress is a prime cause of failure in windshields because the properties of the interlayer are deteriorated, the adhesion to glass or acrylic is reduced and chemical reactions can degrade the electrical systems. Therefore, moisture sealing is a prime concern at Saint-Gobain Sully when designing transparencies.

POLYSULFIDE
Polysulfide is the main sealant material employed in Saint-Gobain Sully, because of its superior erosion and moisture resistance. It can also be applied around the entire periphery of the facing interlayer to form an erosion resistant hump seal over the face-ply.

Z-PROFILE
Some windows include a stainless steel Z-profile to perfectly seal the facing interlayer. This also helps in reducing the delamination forces, since a better mechanical coupling of the face-ply to the main plies is provided.

Bilayer design

As weight saving remains a prime constraint of helicopter designers, Saint-Gobain Sully has developed a bilayer technology to provide light, birdproof and durable transparencies. For these reasons, Saint-Gobain Sully Bilayer windshields have been selected for AGUSTA 129, EUROCOPTER TIGER and EUROCOPTER SUPER-PUMA Mk2.

Typically, a bilayer windshield is composed of :
A SOLIDION® glass face ply provides the windshield with stiffness and a superior resistance to abrasion, wiper action and chemical aggressions.
A urethane layer making a shock-absorbing membrane to provide the windshield with the required birdproof capability.
A self-healing urethane liner covering the internal face which provides the windshield with anti-spall properties and a fair resistance to abrasion and chemical aggressions. It shows an exceptional durability: flight tests have demonstrated its ability to suffer for 25,000 hours the erosion, chemical attacks, humidity and temperature changes that are assigned to outboard surfaces of aircraft transparencies. The much quieter environment of an inboard surface guarantees a quasi unlimited serviceability when used for internal applications.

Birdproof transparencies

Transparencies enclosing a pilot compartment are particularly vulnerable to damage from birdstrike, especially when severe impacts may be dreaded from high speeds at low altitude. That is why Saint-Gobain Sully owns a bird impact facility and performs bird impact tests in accordance to ASTM F330-79 standards.