Session: 15-01-01: ASME International Undergraduate Research and Design Exposition

Paper Number: 99890

99890 - Structure-Property Relations of Pdms-Based Nanocomposites as a Brain Simulant Material. 

When head is covered by protective gear such as helmet, the actual impact load is directly felt by the outer surface of the helmet. With the advent of new generations of helmet systems, a large fraction of the applied impact force is absorbed by the helmet materials. The long-term goal is to gain fundamental understanding on the head/brain injury sensing capabilities of a conceptual “smart” protective equipment in a dynamic environment. This will be done by trapping living neuron cells inside a realistic “phantom” head model, and then by covering the head with a smart protective layer equipped with a set of sensing elements. The injury scenario studied here includes impact due to rapid acceleration/deceleration. Advanced sensing elements such as EEG can be integrated to the helmet layers for monitoring real-time brain health. To determine whether EEG can be used as a potential on-field sensor for detecting localized brain activity due to exposure to brain trauma, we develop a phantom brain tissue material.

Polydimethylsiloxane (PDMS) is a high-performance polymer since it is easily manufacturable, resistant to oxidation, and has beneficial mechanical and physical properties. Thus, it has a wide range of mechanical engineering, civil engineering, electrical engineering, and biomedical applications. Our interest is to study the feasibility of using PDMS-based nanocomposites as a brain simulant material. Different nanoparticles mixed with PDMS can make nanocomposite materials that allows us to enhance the mechanical strength of pure PDMS. Understanding how the mechanical properties of PDMS are affected by the addition of these conductive particles will allow us to make a head model with both desired mechanical and electrical properties. Two components used to manufacture PDMS are: a silicon base and a curing agent or hardener. Nanocomposites are made by incorporating a filler material with PDMS base before mixing with the hardener. The mixture is then cured, either at room temperature for 24-48 hours, or can be heat treated to cure for shorter time. Several studies have investigated the effect of the PDMS-Hardener mixing ratios on its mechanical properties in an effort to improve PDMS properties. Researchers with different objectives have used different dimensions and die given by ASTM standards for their applications. Depending on the change in cross-sectional areas of samples, the relationship between different proportions of test samples and test results is still an obscure area of research. So, it is considerable to study if a change in the shape of a dog bone specimen influences its stress-strain curves depending on its manufacturing process. This paper analyzes how the stress-strain curves of PDMS specimens are impacted by: a variation in the gage to grip cross-sectional area of a dog bone specimen and when manufactured with different filler materials. For the experiment, we used QSIL 216 Clear Liquid Silicone PDMS Elastomer Encapsulant to make test samples. Composite specimen and PDMS samples with various gage-to-grip cross-sectional area ratios are made using a 10:1 PDMS-Hardener ratio and tested in a universal tensile testing machine. Gage to grip cross-sectional area ratios were changed from 1:1 to 1:10. Two filler materials with distinct conductivities used for our experiment were: copper nanoparticles and graphite powders. Specimen molds with different gage to grip area ratios were made for each case using the same material. For each of the gage to grip ratios, a total of three types of samples have been made, one with just PDMS and two others with filler materials. Type A is PDMS-Hardener, and Type (B-C) are PDMS-Filler-Hardener. For each type of test a minimum of 5 samples have been tested. This brief experiment-based study will assist in making the right decision in choosing the range of sample dimensions for tensile test specimens, and save time and cost for any PDMS-based experiment. The structure-property relations for PDMS will also advance our understanding in using PDMS-based nanocomposites for designing biologically relevant materials.

Presenting Author: Yukti Shinglot The University of Texas at Arlington

Presenting Author Biography: Ms. Yukti Shinglot is an undergraduate student in the Department of Mechanical and Aerospace Engineering at the University of Texas at Arlington. Her research is related to traumatic brain injury mechanisms, sensors, mechanisms of materials, and additive manufacturing.

Authors:

Yukti Shinglot The University of Texas at Arlington
Tina Ko The University of Texas at Arlington
Richie Ranaisa Daru The University of Texas at Arlington
Ashfaq Adnan The University of Texas at Arlington