Determination of minimum waiting time following windshield replacement in direct glazed vehicles fitted with airbags.

Adhesive-bonded windshields have to meet certain minimum performance criteria in the event of an accident. These criteria are laid down in US Federal Motor Vehicle Safety Standards (FMVSS). The adhesive bond must exhibit adequate mechanical strength at the time of the impact. The viscoelastic polyurethane adhesives used for windshield bonding require 1-20 hours before they have attained adequate strength. When carrying out windshield replacements, therefore, it is important to know how long the adhesive needs to cure before the adhesive bond is capable of meeting the minimum strength requirements of FMVSS. Hitherto this waiting time has generally been determined by carrying out one or more crash tests. Depending on the design of the airbag system, considerable additional stresses may be imposed on the windshield bond in the event of a crash. Given the variety of different airbag systems that are now available, there was a need to develop an alternative method that does not rely exclusively on crash testing. The developed method includes high deformation rate testing at the Swiss Federal Institute of Technology Lausanne as well as computer simulation performed by PARS GmbH, Alzenau/Germany. In short, it is now possible to analyse newly developed adhesives in the laboratory at relatively little expense, and thus to determine the necessary waiting times after a windshield replacement without the need for elaborate and costly crash test programs. For the covering abstract see ITRD E116488.