1971-02-01

Nonlacerating Glass Windshields - A New Improved Approach 710867

This study was part of a research program which aimed to develop a laminated glass windshield with a very weak-or almost nonexistent-laceration potential.Two types of new safety windshields were tested. They differed only in the strengthening level of the V.H.R. glass used. In both cases, the very thin 0.050 in (1.2 mm) thick inner sheet and the 0.110 in (2.8 mm) thick outer sheet were made of V.H.R. glass. Nevertheless, the glass of the outer ply had a deliberately limited tensile strength. The polyvinylbutyral plastic interlayer was 0.030 in (0.76 mm) thick.The evaluation of the biomechanical behavior of these windshields was made in a laboratory study described in this paper, and in impact tests with a headform free falling on positioned samples.During the impact, the following were recorded or filmed at high speed: the deceleration peak along two orthogonal axes, the resultant severity index relating to the initial impact and to the plow-in, the tearing length of the plastic interlayer, and finally the laceration potential.The latter was evaluated on basis of the laceration rating scale used by Patrick at Wayne State University. A laceration index was given following the number and size of the cuts measured on the two superposed chamois leathers covering the headform.The experimental parameters whose influence was particularly studied were temperature, impact velocity, impact location, and increase of the mechanical strength of the sheets.The research was sytematically carried out in order to compare the new windshield safety performances with that of the conventional laminated ones.All the results of the measurements were statistically analyzed: parameters of distribution, lines of regression, analysis of correlations, signification tests, etc.The new safety reinforced laminated windshield might be used as a true passive restraint system if the tensile strengths of the reinforced glass are adjusted. This double performance will have to be developed in a later series of simulated crash tests with anesthetized primates, anthropomorphic dummies and, if possible, human cadavers.

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