Instrumentation for microscale measurement and characterization of bio-fibers
Date
2005
Authors
Journal Title
Journal ISSN
Volume Title
Publisher
University of Delaware
Abstract
Recent interest in very small scale fibers has driven testing of these materials for their mechanical properties. Due to the difficulty in handling specimens for testing and measuring small loads and displacements required for deformation, mechanical properties of these fibers have not been widely characterized. Existing technologies used for small scale fiber testing are the designs made for larger scale material testing. There exists a gap between the capabilities of existing technologies and a technology capable of truly quantitative small scale measurements. This work makes steps toward narrowing this gap by integrating small mechanical and electrical designs, enabling high resolution in small scale measurements. ☐ In this work, the design development, modeling and simulation, fabrication, instrumentation and the calibration stages of the small scale tensile testing machine have been made. Conducting experiments on single nylon fibers, the mechanical properties of the material have been analyzed and the performance of the machine has been evaluated. ☐ Design goals include having flexibility for testing of different size specimens at different testing speeds, elimination of factors affecting the accuracy of the tests, such as electrical noise, vibration, and airflow, building a PID controller to control the speed for different strain rate experiments and, implementation of safety precautions for saving the system from being damaged. ☐ A MC9S0GB60 Motorola type microcontroller has been programmed as the base unit in the instrumentation. The instrumentation consists of three main parts: processing analog to digital conversion of the data, controlling the motor by Pulse Width Modulation (PWM) method with a PID control, and implementing the RS232 serial communication protocol between the microcontroller and the PC. ☐ The experimental data indicate the force and displacement resolutions to be 7.676 ±1.510mg and 43.556 ±2.175μm respectively. ☐ Testing of one specimen takes less than a minute using this machine. Therefore, repetitive tests can be carried out efficiently and easily for the analysis of small scale fiber mechanical properties.