Abstract

The four-point bend test is one of the most popular strength testing methods used to test LCD panels. Traditionally, a panel is assumed to be either a monolithic piece of glass or two independent pieces of glass sliding against each other. This paper uses finite element analysis to show that a panel behaves like a monolithic piece of glass in the epoxy region (near the edges) but behaves like two pieces of glass at the center. Assuming a panel to be a monolithic piece of glass may overpredict the stresses by a factor of two at the center. Similarly, assuming a panel to be two pieces of glass may underpredict the stresses by a factor of two at the edges. During four-point testing of a panel, the stresses are not uniform in the load-span region and so finite element analysis is required to obtain an accurate stress distribution.

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2011

S. T. Gulati, J. D. Helfinstine, "Edge strength testing of thin glasses," Int. J. Appl. Glass Sci. 2, 39-46 (2011).

2010

J. Westbrook, Strength Measurements of Thin AMLCD Panels 41, 1073-1076 (2010).

2004

S. T. Gulati, J. F. Bayne, W. R. Powell, J. D. Helfinstine, "Mirror constant for AMLCD glass," Amer. Cer. Soc. Bull. 83, 14-15 (2004).

1995

T. Maruno, N. Murata, "Properties of a UV-curable, durable precision adhesive," J. Adhesion Sci. and Technol. 9, 1343-1355 (1995).

1987

C. V. G. Vallabhan, J. E. Minor, S. R. Nagalla, "Stresses in layered glass units and monolithic glass plates," J. Structural Eng. 113, (1987).

1985

R. A. Behr, J. E. Minor, M. P. Linden, C. V. G. Vallabhan, "Laminated glass units under uniform lateral pressure," J. Structural Eng. 111, (1985).

1965

C. J. Phillips, "The strength and weakness of brittle materials," Amer. Scientist 53, 20-51 (1965).

1921

A. A. Griffith, "The phenomena of rupture and flow in solids," Phil. Trans. Roy. Soc. London A 221, 163-198 (1921).

Amer. Cer. Soc. Bull.

S. T. Gulati, J. F. Bayne, W. R. Powell, J. D. Helfinstine, "Mirror constant for AMLCD glass," Amer. Cer. Soc. Bull. 83, 14-15 (2004).

Amer. Scientist

C. J. Phillips, "The strength and weakness of brittle materials," Amer. Scientist 53, 20-51 (1965).

Int. J. Appl. Glass Sci.

S. T. Gulati, J. D. Helfinstine, "Edge strength testing of thin glasses," Int. J. Appl. Glass Sci. 2, 39-46 (2011).

J. Adhesion Sci. and Technol.

T. Maruno, N. Murata, "Properties of a UV-curable, durable precision adhesive," J. Adhesion Sci. and Technol. 9, 1343-1355 (1995).

J. Structural Eng.

C. V. G. Vallabhan, J. E. Minor, S. R. Nagalla, "Stresses in layered glass units and monolithic glass plates," J. Structural Eng. 113, (1987).

J. Structural Eng.

R. A. Behr, J. E. Minor, M. P. Linden, C. V. G. Vallabhan, "Laminated glass units under uniform lateral pressure," J. Structural Eng. 111, (1985).

Phil. Trans. Roy. Soc. London

A. A. Griffith, "The phenomena of rupture and flow in solids," Phil. Trans. Roy. Soc. London A 221, 163-198 (1921).

Strength Measurements of Thin AMLCD Panels

J. Westbrook, Strength Measurements of Thin AMLCD Panels 41, 1073-1076 (2010).

Other

T. Ono, G. Pai, S. T. Gulati, "A simple correction to thin panel strength value as calculated from 4-point bend test," 16th Int. Display Workshops (IDW) MiyazakiJapan (2009) session FMC5-3.

S. T. Gulati, J. D. Helfinstine, T. Ono, J. C. Lapp, "Behavior of LCD panel during bending," SID Symp. Dig. Tech. Papers pp. 1508-1511.

M.-H. Lin, C.-H. Hsieh, K.-F. Huang, "Strength of LCD panel during bending," Soc. Inf. Display (SID) Symp. Dig. (2010) pp. 1069-1072.

ANSYS Help Manual .

S. T. Gulati, J. D. Helfinstine, J. F. Bayne, W. R. Powell, J. C. Lapp, "Mechanical reliability of LCD panels under static loading," Soc. for Inf. Display (SID) Symp. Dig. (2004) pp. 1593-1596.

Standard Test Method for Monotonic Equibiaxial Flexural Strength of Advanced Ceramics at Ambient Temperature ASTM C1499-09 (2009).

S. T. Gulati, J. T. Westbrook, K. H. Vepakomma, T. Ono, J. S. Kim, "Overview of strength tests for LCD substrates and panels," 18th Int. Display Workshops (IDW) NagoyaJapan (2011) session FMC6-1.

S.-H. Chae, J.-H. Zhao, D. R. Edwards, P. S. Ho, "Verification of ball-on-ring test using finite element analysis," 12th IEEE Intersoc. Conf. on Thermal and Thermomech. Phenomena in Electron. Syst. (ITherm) (2010).

R. Huet, M. Wu, "LCD display strength: Why edge preparation matters," IEEE Int. Conf. on Portable Inf. Devices (PORTABLE07) (2007) pp. 1-4.

S. T. Gulati, J. Westbrook, S. Carley, H. Vepakomma, T. Ono, "Two point bending of thin glass substrate," SID Symp. Dig. Tech. Papers (2011) pp. 652-654.

J. D. Helfinstine, S. T. Gulati, J. F. Bayne, W. R. Powell, J. C. Lapp, "Mechanical reliability of LCD panels under dynamic loading," Soc. for Inf. Display (SID) Symp. Dig. (2004) pp. 1597-1599.

S.-W. Chung, J.-W. Jeong, S. Oh, Y.-J. Moon, I.-Y. Baek, D.-S. Hong, "Drop reliability of glass panel for LCD," 2011 IEEE Electron. Components and Technol. Conf. pp. 1250-1254.

K. H. Vepakomma, S. Carley, J. Kim, "Finite element analysis of ball drop on LCD panels," SID Symp. Dig. Tech. Papers (2012) pp. 675-678.

Standard Test Method for Strength of Glass by Flexure (Determination of Modulus of Rupture) ASTM C158-02 (2007).

J. T. Westbrook, J. F. Bayne, S. H. Carley, K. H. Vepakomma, J. S. Kim, S. T. Gulati, "Four point bending of AMLCD panel," SID Symp. Dig. Tech. Papers (2012) pp. 996-997.

S. Garner, "Flexible glass substrates for roll-to-roll manufacturing," AIMCAL Web Coating Conf. (2011).

Development Labs.,Adherent Technologies, IncAlbuquerqueNM“AT-945 UV curing epoxy resin,” (2012).

Three Bond Co. Ltd.TokyoJapan“Three bond 3025G UV sealant for liquid crystal panels,” (1997).

Development Laboratories,DELO Industrial AdhesivesWindachGermany“DELO-Katiobond UV-curing epoxy resin,” (2009).

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