Investigations on the execution and evaluation of the Pummel test for polyvinyl butyral based interlayers
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SI: CHALLENGING GLASS
Investigations on the execution and evaluation of the Pummel test for polyvinyl butyral based interlayers Miriam Schuster
. Jens Schneider
. Tuong An Nguyen
Received: 1 February 2020 / Accepted: 7 April 2020 The Author(s) 2020
Abstract Laminated safety glass (LSG) is increasingly used as structural element in buildings. Of central importance for safety are the adhesion and the residual load-bearing capacity in the post fractured state. In literature a large number of tests to assess adhesion is mentioned. These include, e.g. peel tests, through-cracked-tensile/-bending tests, VW-pull tests and compressive shear tests. However, especially in industry, the Pummel test is widespread for determining the quality of adhesion in LSG with polyvinyl butyral based interlayers. This test method proves to be simple and quick to carry out: The laminate is stored at - 18 C and then completely destroyed at room temperature with hammer blows. The adhesion level (0–10) is determined by visually comparing the adhering glass fragments with reference pictures or with the help of diagrams and tables which indicate the Pummel value as a function of the free film surface. Pummel value 0 is to be interpreted as no adhesion and Pummel value 10 as very high adhesion. Due to the lack of standardization, the execution and evaluation is very much dependent on the test institution and executive person. This paper shows different Pummel classifications that can currently be found on the market. Subsequently, approaches to the automatization and standardization of the execution and especially the evaluation of the Pummel test are shown. M. Schuster (&) J. Schneider T. A. Nguyen TU Darmstadt, Darmstadt, Germany e-mail: [email protected]
Three image evaluation methods in Matlab are presented, discussed and compared: (1) analysis of binary images, (2) statistical evaluation of the greyscale images and (3) texture analysis using cooccurrence matrices. Keywords Laminated safety glass Adhesion Pummeltest Automatization Digital image evaluation
1 Introduction 1.1 Laminated safety glass The use of glass in the building industry has risen sharply in recent years with the ongoing architectural trend towards transparent structures. In this context, the glass must increasingly meet safety-relevant requirements with regard to breakage and post-breakage behaviour. The unannounced failure of the brittle material glass is countered by the use of laminated safety glass (LSG). According to EN ISO 12543-2 (2011), laminated safety glass, consisting of two or more glass panes that are laminated together to form a package by means of polymer interlayers, must bind the resulting glass splinters after glass breakage and enable a residual load-bearing behaviour of the glazing. Accordingly, the adhesion between glass
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and film plays a decisive role. In laminated safety glass with low to no adhesion, the glass pane will delaminate and after glass
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