Experimental investigation of impact response of composite plates/panels

• Main Author: Gan, Jia Li
• Other Authors: Seah Leong Keey
• Format: Final Year Project
• Language: English
• Published: 2010
• Subjects: DRNTU::Engineering::Materials::Testing of materials
• Online Access: http://hdl.handle.net/10356/40579
• Institution: Nanyang Technological University

In this report, it provides a review of the author‟s results and findings on the impact response of acrylic sandwich panel. Impact-induced cracking and fractured acrylic sandwich plates adhered by araldite epoxy are generated in an instrumented drop- weight impact machine. Damage patterns in the acrylic sheet include radial and ring cracks and, together with slight delamination at the interface, which may cause peeling-off of acrylic material from the sandwich plate. The delamination damage is often accompanied by severe shattering in the acrylic substratum. Theories and plots of load against displacement and time can be used to explain these damage patterns. The impact tests are conducted at various thickness and core size. The experiments involve testing of effects of different impact energy and impact velocity on the energy absorption characteristics of the sandwich panels. Results have shown that smaller the core size, the better it is for impact absorption as small core size can generate high concentration of cores per unit area so it provides the required stiffness in the sandwich panel and also, thicker sandwich panels have much thicker core to provide the stiffness and absorb more impact energy. Varying velocities will caused the energy absorption characteristics to differ where damage will be less localized under low velocity. For low velocity impact, the stiffness of the sandwich panels can influence the amount of energy absorbed, which is the reason why the amount of impact energy absorbed varies from one specimen to another. It can also be concluded that for high velocity the amount of energy absorbed is almost the same irrespective of specimens‟ stiffness and the damage on the point of impact. Material of crossheads are changed to give a lighter impactor, producing damage states characterized by residual dent depths that are comparable to the core thickness, accompanied by visible facesheet fractures. As far as is possible, the aim throughout has been to relate the behavior and characteristics of the acrylic sandwich panels. Acrylic composites have some limitations which are their response to localize impact loading. The manner it dissipates the incident kinetic energy of the projectile is different from metal. The datas collected from these impact tests are generated in the form of a graph of load versus time and displacement. Comparisons of results are made between past year FYP students and other journal papers. Furthermore, acrylic sandwich is strongly influenced by the material properties such as strength toughness, adhesive techniques and bonding strength while the latter can be affected by the specimen geometry and loading parameters. In the last chapter, the author will also list out some constructive recommendations and conclude on what the author has achieved during the final year project.