A Foundational Approach to Extrusion and Compounding

With a history of nearly 200 years, polymer processing and compounding is constantly changing to fit the material science needs of the era. Exposure of undergraduate students to the technology and practices used in industry today in a lab setting would create new opportunities for experiential learning and growth. The objective was to set up a 0.75”, 25 L/D Thermo Haake single screw extruder for lab use and run trials of material in a single screw extruder to set up a basis for experiments. Trials were run of co-polyester resin through a single screw extruder with carbon fiber additives varying at 0, 5, and 10% as a reinforcing agent and screw speed to determine degree of mixing vs tensile stress. Pellets were then molded and tensile stress and Young’s Modulus were determined, with a linear trend with slopes of 383.8 MPA/% and 28930 MPA/% vs percent carbon fiber loading were found, respectively. More data points are needed to definitively say whether the screw speed had an effect on tensile data with failure to reject H0 in a one-way ANOVA test at each fiber loading. This failure indicates that there is no effect on mixing of polymer and tensile data

Development of a Closed-Loop Force Reduction Mechanism in a Gait Rehabilitation Device

Elliptical trainers are prescribed in rehabilitative exercise but difficult to implement in populations with significant functional gait deficits. Typical elliptical machines do not mimic normal gait and therefore require modifications for clinical rehabilitation. This research builds on previous modifications of an elliptical trainer designed to simulate level-surface walking. This design differed from a commercial version. It included articulated footplates and an electromechanically-driven virtual-cam to control footplate position. Ankle dorsiflexion elicited lower-extremity muscle spasticity which produced an unwanted gait variant during stroke patient testing. Spasticity is a hyperexcitable stretch reflex causing inefficient gait. This project’s purpose was to develop an autonomous cam-profile adjustment to optimize the device’s rehabilitation potential. Foot-to-footplate forces were measured in stroke patients and compared to normative data. Greater than normal forces were considered spastic. An embedded controller was designed to reduce footplate forces via real-time cam-profile attenuation. A simulated spastic dorsiflexion load successfully proved the algorithm’s efficacy