Interpretation ID: aiam4307
Director
Automotive Safety Engineering
Environmental Activities Staff
General Motors Corporation
General Motors Technical Center
30400 Mound Road
Warren
MI 48090-9015;
Dear Mr. Rogers: This responds to the letter (USG 2496) from Mr. David Martin concernin how the penetration resistance requirements of Standard No. 205, *Glazing Materials*, would apply to a piece of glazing that has two plys. I regret the delay in our response and hope the following discussion answers the questions raised by General Motors.; The letter explained that the glass manufacturing industry i continuing to develop new types of windshields to reduce facial lacerations. It further explained that a new type of glazing, referred to in the letter as '2-ply' glazing, has been developed which 'differs from the traditional High Penetration Resistant (HPR) windshield and the first generation antilacerative windshields in that it consists of one 'outer' glass ply and an 'inner' plastic laminate.'; The letter stated that there is a question about certifying an item o 2-ply glazing to the requirements of the penetration resistance test (Test No. 26 in ANS Z26.1) that is incorporated in Standard No. 205. In that test, a flat glass sample is supported in a wooden frame and must not allow a 5-pound steel ball to pass through it when the ball is dropped onto the supported sample from a height of 12 feet.; The letter further explains that, >>>When an HPR sample is laid on the wooden frame and the ball i dropped onto it, it cracks and bends somewhat but it is sufficiently rigid so as to remain on the text fixture frame and allow the test to measure its ability to resist penetration of the ball. However, when a 2-ply sample is tested in the traditional manner to Test No. 26, it cracks and bends sufficiently so that the glass test sample falls through the test frame. Thus, the test does not evaluate the ability of the sample to resist penetration of the ball, as is the stated intent of the test. On the other hand, if the traditional test method is appropriately adapted (such as clamping) to retain the 2-ply sample in the test frame, the test does, in fact, serve its intended purpose.'<<<; The letter requests the agency to adopt, by interpretation, modification of the test procedure to permit the retention of a piece of 2-ply glazing in the test frame.; Based on the information you have provided the agency, it appears tha the test procedure used in the penetration resistance test is not appropriate for the newly developed 2-ply windshield. As correctly noted in General Motor's letter, the purpose of the test is to determine whether an item of glazing has satisfactory penetration resistance. Because of (sic) 2-ply glazing material has more flexibility than conventional HPR glazing, the 2-ply material merely flexs (sic) and drops through the wooden test frame when it is struck by the steel ball. Thus, it is not possible to evaluate the penetration resistance of the 2-ply material in the same manner as conventional HPR glazing.; I do not, however, believe that the agency can adopt, b interpretation, a change in the test procedure you have requested. At present, the test procedure provides that the test sample is to be supported in a square wooden frame. The frame, as depicted in Figure 1 of ANS Z26.1, is made so that there is a 7/16 inch lip around the inside edge of the frame. The glass sample is placed inside the frame and supported by the lip during the drop test. The test procedure does not provide for clamping or otherwise holding the sample in place during the drop test.; To address the problem you have raised and to ensure objectivity in th drop test procedure, the agency believes it is necessary to amend the standard to establish uniform requirements for providing additional support to 2-ply glazing materials during the drop test. We will treat the General Motors letter as a petition for rulemaking to amend the standard to set a new test procedure for the impact resistance test. In considering possible amendments, we will carefully examine the work we understand is being done by the International Standards Organization on the clamping of test samples for the drop test.; If you have any further questions, please let me know. Sincerely, Erika Z. Jones, Chief Counsel