SHEAR THICKENING FLUID-FABRIC COMPOSITE :SHEAR THICKENING FLUID-FABRIC COMPOSITE MALAYSIAN TECHNOLOGIES EXPO. (MTE) 19 – 21 FEB. 2009 MOHD SUHAIRUL B. SUHAIMI flit85@yahoo.com 012-9440290 PM DR RAHMAH MOHAMED drrahmah@gmail.com 019-3568847 AHMAD FAIZA MOHD ahmadfaizamohd@yahoo.com 019-2727076


Slide 2:OUTLINE >> BACKGROUND - Shear thickening fluid (STFs) - STF – Fabric composites >> MATERIALS - STF components and preparation -Fabric and STF impregnation >> TESTING - Stab testing .. Drop tower - spike >>FIELDABILITY >> CONCLUSIONS


Shear Thickening Fluid (STF) :Shear Thickening Fluid (STF) 0.5 µm colloidal silica particles


Objective :Objective • Impregnate STF into fabric to improve its protective properties – STF should be flowable and deformable during low speed, low deformation events • STF-fabric should be drapable, flexible like ordinary fabrics – STF should be rigid during high speed, high deformation events • STF may enhance the ability of the fabric to protect against threats such as projectiles and sharp objects • U.S. Army applications – Improve flexbility, reduce weight and thickness of vest materials – Enable flexible, low thickness extremities protection PASGT Vest Kevlar® 29


Materials :Materials STF – 90 nm PMS particles – Polyethylene glycol carrier fluid – Silica particles added at 0.4 volume fraction, mixed to achieve high dispersion • Fabrics ? all fabric plain woven – Kevlar ? Hexcel-Schwebel Style 706 • 600 denier KM-2, 34x34 yarns per inch (ypi), 0.0369 lbm/ft2 (psf) 90nm PMS


Fabric Impregnation :Fabric Impregnation Processing route – STF diluted in ethanol – Fabric dipped into solution – Fabric squeezed in roller to remove excess – Fabric dried for 30 minutes at 150ºF to remove acetone Impregnate fabrics at ~20% wt STF Control STF wt% by aceton:STF ratio in dip bath


Stab Resistance Testing :Stab Resistance Testing Testing method based on NIJ Standard 115.00 (2000) – Drop tower with two types of impactors Ice pick – Stab target backed by multi-layer foam support – Measure depth of penetration of spike into backing • Witness papers between foam layers determine whether puncture occurred – Vary impact energy by varying drop height (velocity) and drop mass


Spike Stab Results :Spike Stab Results • STF-Kevlar show consistently less penetration depth than neat Kevlar – For lowest impact velocities, STF-Kevlar never penetrated • Note that areal density of targets are comparable, but STF-Kevlar composite uses fewer total layers of Kevlar fabric


Fieldability :Fieldability Manufacturability – Dip process for STF fabrication should be scalable – Base materials for STF (silica, PEG) are commodity materials Environmental resistance - STF can be further engineered to achieve high levels of thermal and moisture resistance. Health - STF components are benign and non-toxic Some care required in handling dry colloidal silica, which aerosolizes easily, during processing


Conclusions :Conclusions STF addition significantly improves puncture resistance of fabrics – At same areal density, STF-Kevlar has dramatically higher spike protection than STF-COTTON – At same areal density, STF-Kevlar and STF-COTTON offer comparable knife protection However, STF-Kevlar has significantly fewer fabric layers than neat Kevlar ? STF-Kevlar thinner, more flexible than neat fabric – Mechanisms of STF performance apply to multiple threats Other work – Ballistic properties • Y.S. Lee, E.D. Wetzel, and N.J. Wagner. “The ballistic impact characteristics of Kevlar woven fabrics impregnated with a colloidal shear thickening fluid.” J. Mat. Sci. v38 n13 p2825-2833. 2003.