Edgewise Drop Impact on Liquid Crystal Display (LCD) glass panels

The LCD glass substrate industry seems to be growing rapidly with the increasing popularity of LCD TV's, notebook computers and wide screen mobile phones. Market research says that LCD glass substrates are typically as thin as 0.3 to 0.8 mm. Since LCD glass is widely used in the electronics industry, manufacturers are interested in the mechanical properties, especially the impact resistance, to analyze the level of impact that these materials resist in case of random drops, blows, collisions etc.

To replicate real life impacts closely on such materials, the glass industry is interested in analyzing impact strength in edgewise position as shown in the picture. Hence, in addition to the standard flatwise drop weight test we developed a fixture on Instron 9450. Drop Weight Impact Tester for performing an edgewise impact on LCD glass coupon specimens. This design of the fixture is intended to help the user understand material failure at different angles and positions apart from 0º and/or 90º. The device is equipped with an auto centering device to keep the impact point unvaried at all times. This fixture can perform edgewise impacts on specimens at various angles like 5º, 15º, 30º, 45º and 60º.

One of the challenges faced when conducting edgewise impact tests is off-centered impact, which would cause erroneous results from the side load experienced by the striker. To avoid this problem, the striker insert used was semi-cylindrical instead of semi-spherical. We impacted 100 x 100 mm specimens of 0.7 mm thickness using a 20 mm diameter semi-cylindrical insert oriented with its axis perpendicular to the edge of the specimen. The absorbed energy for this particular grade of LCD glass specimens at 0º and 30º ranged around an average value of 0.479 J and 0.135 J respectively.

We see a possibility of broader range of testing to be accomplished on different materials in future with the development of such an impact capability.