Study of the behavior of Shape Memory Polymers in the Active Disassembly Process

This paper reports on a research experience for a teacher in researching the behavior of shape memory polymers. The use of active disassembly using smart materials (ADSM) can be an alternative, with the potential to enable a broad range of electronic devices to be actively disassembled at the same time, reducing the cost of the manual labor or machine operation needed to disassemble the products. Shape memory polymers (SMP) are promising materials for this application. The main aim of the present study was to create SMP snap-fits and analyze the effect design parameters on the disassemble time. Six sets of snap-fits with different design parameters were manufactured form a commercial SMP Veritex. They were tested and the disassemble time was analyzed. According to the results, design parameters showed to have a slight influence in the disassemble time during the active disassemble process. A learning module based on the legacy cycle concept is being developed and it challenges students to think through new applications for the shape memory polymers. This learning module will be introduced into a high school mathematics class during the 2011-2012 school year. Assessment of the student’s performance will be carried out and reported. Overview of the 2011 Research During the summer 2011 I had the opportunity to participate in the Research Experience for Teachers program at the Texas A&M University-Kingsville. This program was a total learning experience, in which I had the opportunity to develop a high level scientific research project. I also got a chance to get to know ten other educators that were selected the same as I to participate in the program. Throughout the six weeks of the summer that this program lasted, I was working on a research project titled “Study of the behavior of Shape Memory Polymers in the Active Disassembly Process” under the supervision of Dr. Hua Li. This project focused on active disassembly using smart materials (ADSM) as an alternative, with the potential to enable a broad range of electronic devices to be actively disassembled at the same time, reducing the cost of the manual labor or machine operation needed to disassemble the products 1-5 . One of the main aspects of this project that excited and motivated me the most was to be working with smart materials such as Shape Memory Polymers 6 (SMPs). These materials have the characteristic of automatically changing form when stimulated by externally trigger 7 , such as heat. Due to this characteristic, the SMPs are promising materials for several applications, such as the Active Disassembly process. The main aim of the research project was to create SMP snap-fits and analyze the effect of the design parameters on the disassembly time. Six sets of snap-fits with different design parameters were manufactured form a commercial SMP called Veritex. The design parameters to manufacture the snap-fit prototypes in their release position were chosen according to various factors analyzed during a pre-test process. The pre-test consisted of heating the material to different temperatures (75, 85, and 95 °C) and bending it to a desired angle. For experimentation, a testing device that simulates a housing case was design and built. For the test a spring was attached to the center of the case, and the walls were machined in order to attach the snap-fits. Four pieces simulating recesses were manufactured and screwed to the cover. The active disassembly tests were carried out in three stages. The first stage was to train the material, in other words, modify its original shape to a temporary shape (assembly position). The second stage of the tests consisted in assemble or close the testing device by means of the snap-fits joints. Finally, during the third stage the testing device was placed inside the oven at 85 °C to activate the snap-fits and release the snap-fit joint. When this happens, the spring ejects the cover disassembling the device. We define as a successful disassembly when all the snap-fits recover its original shape and the cover was ejected by the spring force. During the test, the testing device was monitored every 30 seconds by visual inspection through a 4 inch diameter window on one side of the oven. The disassembly time for each experiment was recorded. Three repetitions for each set of snap-fits were done. According to the results, design parameters showed to have a slight influence in the disassembly time during the active disassemble process. In my opinion, the most significant accomplishments of the research experience were: Development of snap-fits using SMP A state of the art technology was first developed starting with my designs on pen and paper and then materialized into real components using a CNC machine. The CNC machine grew a spark of interest in me during this project which motivated me to research its functionality in detail. At the spike of my interest were various projects’ that came to mind to implement with my students in my math class using a CNC machine. Development of the testing device This took place in a short amount of time which included the design and manufacturing of a functional testing device. During the manufacture of this device I learned a lot in the workshop. My original designs of the testing device were evolving little by little. I have never had the responsibility of manufacture something by myself. In this project, I had the opportunity to participate actively on the manufacture of the components for the testing device working in the workshop and using equipment such as milling machine, lathe, drill, band saw and also precision measuring equipment. This testing device, besides being a key piece for our experimentation, also remained in the hands of the University for future research on this topic. Experimentation process During the experimentation, I had the satisfaction of proving my own designs, both snap fits and testing device. Regardless of the outcome of the experiments, the experience of seeing my designs working was priceless. Research paper and poster presentation Writing a scientific research paper for disseminating the results of the experiments was a challenge due to the short period of time to complete the project. More than a research paper, I see it as a mini thesis. However, authoring a research paper and see your own work expressed on paper to be shared with others is an indescribable experience that makes me proud. I think that to share this experience through a research paper or a poster presentation can be very motivating for many students, which can result in the courage that many of them need to embark on the great adventure of the world of the science and technology. Background of the Legacy Cycle A component of the RET experience was the development of a Legacy Cycle inquiry lesson unit intended to connect the teacher’s research to high school mathematics curriculum standards. The legacy cycle that I developed during the summer 2011 called “Smart Materials in Action” is planned to be implemented with my students during spring 2012 at PSJA High School. PSJA High School is a public school in San Juan, Texas and is one of the four PSJA district's high schools. It educates over 2,500 students. Pharr-San Juan-Alamo Independent School District is a district that caters to over 31,000 students in the tri-city area in Texas. PSJA ISD houses students from three different cities, who come from similar backgrounds and way of life. The student body at PSJA ISD is 98.97% Hispanic, 85.37% economically disadvantaged and 73.16% at risk due to low socioeconomic status. With the district’s proximity to Mexico, 41.36% of the students are considered Limited English Proficient (LEP) with Spanish being the language spoken at home. Despite those figures, PSJA ISD has maintained a culture of pride and excellence. Known for its “children first” environment it has actively taken those challenges and has helped motivate students to pursue an education beyond high school. The “Smart Materials in Action” Legacy Cycle will be implemented with 70 students approximately from two Algebra I classes and two Algebra II classes, including 40 freshmen and 30 juniors respectively. As part of a Dual Language Program one of my Algebra I classes is lectured in the Spanish language. According to the experience and the knowledge learned during the research project in the summer, I designed the Legacy Cycle, "Smart Materials in Action" which will challenge students to think of an existing application and enhance its functionality by means of a new component produced from an SMP, taking advantage of the fact that it can change shape by itself when heat is applied. The new prototypes will be tested on scale models and from the experiments, students will receive and record information such as temperature, strain and time. Before I began the Legacy Cycle, I obtained a grant from the RET program to purchase the materials needed for implementation. The detailed list of materials is showed below: Shape memory polymer For the Legacy Cycle, 4” x 6” and 12” x 12” 3-ply Veritex Shape Memory Composite Sheets were acquired to manufacture the new components. We have previous knowledge on this material since it is the same that was used during the summer.