Project Report

A sandwich composite is a unique layup of different materials that have the beneficial properties of being lightweight yet strong and stiff. They also have the ability to absorb impact energy due to the high compressibility of its thick core material. These kinds of structures can be found in the product components of several different industries such as aerospace, naval, wind turbine, and electronics. I have developed a structural theory for my PhD at Georgia Institute of Technology that models the core material's compressibility. This theory can be used to predict the behavior of the composite under different loading conditions. The goal of my collaborative research at the Centre for Advanced Composites Materials (CACM) at the University of Auckland in New Zealand was to conduct dynamic impact experiments alongside experienced experimentalists on sandwich composite test specimens in order to validate the new sandwich composite theory. The researchers at CACM taught me how to manufacture the sandwich composites using a vacuum resin infusion method. This method involves laying up the different materials dry, compacting them under vacuum, and then using the vacuum to pull the resin (glue material) in from outside the bag (or mold) which subsequently progresses through the dry layup. After the sandwich specimens were made we conducted three-point bend impact experiments where the panels were supported on the bottom near the edges and a mass was dropped on the top center of the composite. In order to validate the theory we attached strain gauges on the top and bottom of the panel. The strain gauges measured the amount of deformation of the panel during the impact. I compared the predictions from my theory to the measured data and found that my theory can capture the behavior of the sandwich composite just after impact. During the impact the specimens bend. It is well known that when the specimens bend upwards, the top material is in compression and the bottom material is tension. However, during a short time after impact, the specimen exhibited areas of tension on the compression side, and some areas of compression on the tension side. Later in time the top and bottom of the specimen behaved in the well known way. The experiment and the new theory captured this behavior well just after impact. Beyond some time, but still during impact, structural damping began to play a role. I was also able to validate my theory with some additional experimental data the host researchers had conducted before my arrival. We wrote and submitted a collaborative article to a journal on validationg my theory to the experimental results they had on the wrinkling behavior of sandwich composite when they undergo a purely compressive load. Also during my work at CACM, I met other researchers in the area of composites, who studied the manufacturing processes and mechanics of new composite materials. My stay at CACM allowed me to make contacts that I will continue to correspond with. I will continue to collaborate with my host researchers to compare the new theory to their experimental data.

National Science Foundation (NSF)
Office of International and Integrative Activities (IIA)
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Carter Kimsey
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Phan Catherine N
United States
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