Session: 12-29-01: Mechanics of Soft Materials

Paper Number: 150571

150571 - Dynamic Tensile Response of Soft Material 

Soft materials with low mechanical impedance and strength are extensively used as shock‑absorbing components in industries such as automotive, aerospace, transportation, and portable electronics. Soft materials are also used to make wearable electronics due to their flexibility and ability to conform to the body's contours while maintaining functionality and comfort. Understanding their mechanical properties, especially under impact, is crucial for their efficient utilization. The mechanical behavior of soft materials is highly sensitive to strain rates. During high strain loading such as impacts, the dynamic response and failure patterns of these materials can differ significantly from those under slower, quasi-static loading. However, there are limited studies on their tensile response under medium strain rates (10¹/s to 10³/s). Here, we report our recent experimental studies using Polydimethylsiloxane (PDMS) as an example material. PDMS has become widely favored because of its distinctive physical properties, compatibility with biological systems, thermal resilience, and cost-effectiveness in production. From a mechanical property standpoint, PDMS is classified as a soft viscoelastic material exhibiting large deformation and rate dependent characteristics. In a previous study, we characterized how PDMS with pre-determined defects behave under quasi-static loading conditions. As a continuation, the objective of this study was to analyze how crack propagation of PDMS samples with defects behave under dynamic loading conditions and how it differs from a quasi-static test. PDMS was manufactured by mixing a base with a curing agent using the standard mixing ratio 10:1. The mixture was de-gassed in a pressure chamber to remove air bubbles and reduce inhomogeneity. The prepared mixture is poured into custom 3D printed molds to create three rectangular PDMS samples measuring 152 mm × 25 mm simultaneously. Each mold was designed with elliptical holes of predetermined size to create rectangular PDMS samples featuring defects of varying sizes at their centers. The first type of sample contained no defect, the second contained a 5 mm by 1 mm elliptical horizontal defect, the third contained a 5 mm by 5 mm circular defect, and the fourth contained a 1 mm by 5 mm elliptical vertical defect. Once the mixture was carefully poured into each mold, it was placed at room temperature (25◦C) to cure for 24 hours. Our previous study used the Shimadzu’s AGS-X series universal testing machine along with a stroke rate of 5 mm/min (which translates to a strain rate of 0.0006 s^-1) to maintain quasi-equilibrium in the samples. With the drop tower based tensile test setup, strain rates up to 1000 s^‑1 can be obtained. At elevated strain rates, PDMS samples exhibit characteristics reminiscent of brittle behavior, showing diminished capacity to absorb energy but demonstrating higher tensile strength compared to their performance at lower strain rates. This behavior suggests that under dynamic loading conditions, PDMS tends to experience quicker failure with less deformation before reaching its ultimate tensile strength. This contrasts with its behavior at lower strain rates, where the material typically displays greater ductility and energy absorption capabilities, allowing it to deform more extensively before eventual failure. Understanding these differences is essential for designing PDMS components that can withstand the specific mechanical demands imposed by varying strain rates encountered in different applications.

Presenting Author: Yukti Shinglot The University of Texas at Arlington

Presenting Author Biography: Yukti Shinglot is a Graduate Student at the University of Texas at Arlington (UTA). She is pursuing a Master of Science in Aerospace Engineering with a thesis focus on the Mechanics of Materials. Her research interests include the tensile response of soft materials and the development of additively manufactured protective material to mitigate laser exposure.

Authors:

Yukti Shinglot The University of Texas at Arlington
Tina Ko The University of Texas at Arlington
John Cross The University of Texas at Arlington
Ashfaq Adnan The University of Texas at Arlington