Energy Absorption Behaviour of Kevlar Impregnated with Shear Thickening Fluid Under Low Velocity Impact

Abstract

Shear thickening fluid (STF) has been exploited in combination with high performance fabric such as Kevlar to produce new thin, flexible, lightweight, and inexpensive material that is equivalent or even better performance than existing body protection materials. This area of research has received a great deal of attention and number of publications related to STF studies has remarkably increasing in the past decade. However, up until now, there are still no clear and specific method or formulation to the production of smart materials from STF. Hence, the purpose of this study is to investigate the effect of different impregnation methods of Kevlar/STF fabric composites to the energy absorption behaviour of the composites under low velocity impact and to study the effect of STF-impregnated Kevlar to inter-yarn friction properties to support the mechanism of energy absorption. The composition of STF used in this study were 15 weight percentage (wt%) and 20 wt%. The first method (Method A) used to fabricate Kevlar/STF composites was adopted from previous studies, where dry STF was produced prior to the impregnation process. Ethanol was added to the STF to improve dispersibility of the mixture and after that the sample was dried in the oven to remove the ethanol. For the second method (Method B), Kevlar was directly impregnated with the mixture of ethanol, fumed silica particles and polyethylene glycol (PEG), before drying in the oven to produce the Kevlar/STF fabric composites. The performance of the composites fabricated using the first and second methods was analysed through drop weight impact test under low velocity and single yarn pull-out test. Kevlar impregnated with 20 wt% of STF showed significantly better performance than Kevlar impregnated with STF of 15 wt%. Between the first and second method, the latter shows better improvement by 19% in terms of the energy absorption.