Failure of plastic structures due to drop impact

• Main Author: Yuen, Shuqin.
• Other Authors: Chai Gin Boay
• Format: Final Year Project
• Language: English
• Published: 2009
• Subjects: DRNTU::Engineering::Materials::Mechanical strength of materials
• Online Access: http://hdl.handle.net/10356/16827
• Institution: Nanyang Technological University

This report presents the experimental investigation and analysis of the failure of three different types of test specimens subjected to transverse point load. One test specimen type is made of two acrylic face skins bonded to a Nomex honeycomb core in the middle. The second type of test specimen is made of two acrylic face skins that are not bonded to its honeycomb core. The factor of the honeycomb sandwich specimens is the thickness of the acrylic facings, varying of 1.5mm, 2mm and 3mm. The final type of specimen is plain acrylics sheets of varying thickness of 1.5mm, 2mm and 3mm. Variation of the specimens enable the comparison of their performance in terms of the maximum load attainable, total energy absorbed and the deflection of the upper facing or acrylic. The transverse point loads include impact load whereby a tup was dropped onto each specimen at varying impact speeds of 0.7m/s, 0.8m/s, 0.9m/s, 1.7m/s and 2.3m/s, and a static load in which the tup was quasi-statically moved downwards. This was done to investigate the fracture differences at varying speeds. It was found that specimens with thicker face skins were able to absorb the most energy generally, and that the higher the velocity of the impact test, the higher is the energy absorbed and maximum load that can be achieved. Comparisons of the fracture mechanisms after these two types of tests were carried out, and it was found that bonded honeycomb sandwich panels demonstrated the best performance in the impact test, but the worst in the quasi-static test. Also, specimens that underwent quasi-static load were able to absorb higher amount of energy compared to those that underwent the impact load. Analysis and a study of the specimens were done. Recommendations for future work were also suggested.