High performance bonding of aircraft windshields

Citation

(1998), "High performance bonding of aircraft windshields", Aircraft Engineering and Aerospace Technology, Vol. 70 No. 3. https://doi.org/10.1108/aeat.1998.12770cad.012

High performance bonding of aircraft windshields

High performance bonding of aircraft windshields

Keywords Adhesives, Aircraft, Ciba, Windshields

Aircraft windshield production requires high performance materials and meticulous assembly procedures. Sierracin/Sylmar Corporation, Sylmar, California, a leading supplier of windshields for commercial and military aircraft, is using a fast cure, durable polyurethane adhesive from Ciba Specialty Chemicals to bond a nylon feintbreed acrylic and epoxy edge attachment onto vacuum- formed acrylic sheet to produce high quality windshields.

Adhesive selection for the application was critical since Sierracin had found that many products cause crazing on the acrylic sheet. These fine stress fractures can result in cracks when subjected to the extremes of temperature to which the windshields are normally exposed. This ultimately compromises the structural integrity of the windshield, requiring it to be prematurely scrapped. After careful evaluation of a variety of adhesives, Sierracin chose Uralane^® 5774-A/B urethane adhesive from Ciba Specialty Chemicals for a really effective combination of performance characteristics.

According to Connie Maglalang, materials laboratory group leader at Sierracin:

The Uralane adhesive is easy to apply and resists crazing on acrylic windshield panels. It also provides us with the strength needed at elevated temperatures.

Uralane 5774-A/B is a tough polyurethane which is specifically formulated for use on dissimilar substrates. Once cured, the adhesive exhibits a lap shear strength of 1,400psi (10Mpa) on polycarbonate at room temperature and 900psi (6MPa) at 180°F (80°C). Uralane 5774-A/B is qualified to the following specifications: Airbus AIMS 10-04-001, Boeing BMS 5-105, Type 5, McDonnell-Douglas DPM 5892 and Learjet LES 1359.

Sierracin technicians begin windshield assembly by covering both sides of a formed acrylic panel with protective film and masking tape, leaving a several inches-wide border around the perimeter. The exposed surfaces are then hand sanded to optimise adhesion, wiped clean and coated with an epoxy based primer. Tape is then added around the edges of the covering film to help prevent excess adhesive from creeping onto the clear windshield.

Uralane 5774-A/B is mixed in a ratio 2:1, resin to hardener (by volume) and applied using a spatula. "The Uralane adhesive is easy to handle with its 15-20 minutes work life" reports Julian Galingan, production manager for Sierracin.

Once the frame is positioned on the adhesive coated windshield panel, locator pins are inserted. The pins hold the frame in place until the clamps can be added to firmly secure assembly components while the adhesive cures. Technicians can handle the bonded area after 4hrs: the full cure cycle is seven days at 77°F (25°C). The protective tapes and films are removed and the windshield is completed by fixing the retainers, bolts and pins needed for the final attachment to the airframe. Finally, each windshield undergoes a comprehensive quality control check before being shipped to the customer.

Ciba Specialty Chemicals delivers high performance bonding to aircraft windshield manufacture

Uralane 5774-A/B is available in bulk cans for high volume use and dual cartridges which allow waste free and accurate dispensing through disposable mixing nozzles.

Cure may be accelerated by allowing the polyurethane to gel at room temperature followed by two to four hours at 150°F (660°C) or one to two hours at 200°F (93°C).

Details from Customer Service Centre, Ciba Specialty Chemicals Ltd. Tel: +44 (0)1223 493000; Fax: +44 (0)1223 493322; E-mail: carla.watson@gbdu.mhs.ciba.com