A parametric study of guided mechanical waves in windshields: a three–layer laminated structure Shihong Huo and Henrique Reis * Department of Industrial and Enterprise Systems Engineering, University of Illinois at Urbana-Champaign, 104 S. Mathews Ave., Urbana, IL, USA 61801 ABSTRACT A parametric study of guided mechanical wave propagation in laminated safety glass (windshields) is presented. Laminated safety glass is considered a three layered structure modeled as a viscoelastic layer bonded by two elastic layers, i.e., glass plates. The interface between each of the two bonded layers is modeled as a bed of longitudinal and shear linear springs. The spring constants are estimated using surface analysis in conjunction with atomic force microscopy and profilometer analysis. Attenuation due to material absorption of the viscoelastic interlayer is considered while calculating the dispersion curves for the system. The dependence of phase and energy velocities, attenuation, and resonance frequencies, upon variations of material properties (e.g., modulus of elasticity, Poisson’s ratio, and longitudinal and shear ultrasonic material attenuation) is discussed. The relative physical dimensions (i.e., layer thickness variation of each layer) influence upon guided wave behavior is also presented and discussed. Results are applicable to any similar three-layer laminated structure. Keywords: Guided waves, laminated safety glass, windshields, attenuation 1. INTRODUCTION Laminated safety glass is used in the automobile industry (i.e., windshields) and in architectural applications. It is typically a three–layered laminated structure consisting of a viscoelastic plastic interlayer, such as a layer of poly vinyl butyral (PVB) or Butacite, surrounded by two adjacent elastic glass plates. Figure 1 shows a laminated safety glass, and Tables 1 and 2 show typical material properties used in the three layered structure. The main purpose of this study is to investigate the dependence of guided mechanical wave behavior upon material and geometric variations of this three- layered system. The results should be applicable to similar layered systems. Figure 1: Schematic diagram of guided wave measuring system to assess levels of adhesion in laminated safety glass samples. Figure is duplicated after Huo and Reis 14 . Function-Generator and Amplifier Computer A/D Card Band-Pass Filter & Amplifier Plastic Interlayer Receiving Transducer Sending Transducer Glass Plates Sensors and Smart Structures Technologies for Civil, Mechanical, and Aerospace Systems 2008, edited by Masayoshi Tomizuka, Proc. of SPIE Vol. 6932, 69322O, (2008) 0277-786X/08/$18 · doi: 10.1117/12.768005 Proc. of SPIE Vol. 6932 69322O-1 2008 SPIE Digital Library -- Subscriber Archive Copy