Low and high velocity impact evaluation of self-stiffening gel

• Main Author: Tng, Jerrell
• Other Authors: Leong Kah Fai
• Format: Final Year Project
• Language: English
• Published: Nanyang Technological University 2021
• Subjects: Engineering::Materials::Material testing and characterization; Engineering::Mechanical engineering
• Online Access: https://hdl.handle.net/10356/150206
• Institution: Nanyang Technological University

This study analyses the dynamic mechanical properties and behaviour of pure shear-stiffening gel (SSG) and evaluates its potential for sports protective equipment (SPE). The SSG, polyborondimethylsiloxane (PBDMS), was tested at three different types of velocities ranges, (a) low; (b) medium; (c) high. The different velocities correspond to the different situation the PBDMS is subjected to as well as the three different states of PBDMS. The lack of comfort and mobility of most SPE has led to higher sports injury rates, demanding the need for new materials for SPE. Even though SSG-based foam variants have been used in the SPE industry, the use of pure SSG has not been evaluated. Also, the thickness of SSG in relation to its impact absorption performance has not been clarified. The small amplitude oscillatory analysis (SAOS) was used to evaluate the low velocity properties of PBDMS. The impact drop weight test was to quantify how thickness affect various factors of PBDMS and to compare PBDMS with EVA. Split Hopkinson’s pressure bar (SHPB) test was used to test the PBDMS sample at high velocity. Results from the three test indicates the three different states of PBDMS: (a) viscous; (b) elastic; (c) glassy.Under the angular frequency of 11.1 rad/s, PBDMS exhibits liquid-like behaviour, indicating high comfort and mobility for low velocity activities. At impact energy of 15 J and above, the 11 mm PBDMS sample outperforms the 11 mm Ethyl vinyl acetate (EVA) sample in loading capacity and elastic recovery. Although, high velocity studies show that PBDMS behaves like a glassy solid and shatters at 4980/s, these velocities are highly unachievable under normal sporting circumstances. These results suggest that the desirable viscoelastic properties of PBDMS, compared to EVA, making it a superior material for SPE.