Impact Poster Final

Energy Absorption in nanocomposites at different strain rates Swasti Gupta, P. Raju Mantena, Ahmed Al-Ostaz Composite Structures and Nano Engineering Research Group (CSNERG)- University of Mississippi

Introduction Objectives

• Characterize impact and blast resistant properties of nanocomposites • Maximize energy absorption at varying strain rates

Nanocomposites

Test methods

Derakane 411-350 vinyl ester reinforced with •1.25 & 2.5 wt percent exfoliated graphite nanoplatelets •1.25 & 2.5 wt percent cloisite 30B nanoclay

•Low-velocity impact •Shock tube •Split Hopkinson bar

Experimental Testing and Results Low-velocity Impact Testing o ASTM D-6110-06 with sample size of 127 mm x 9.9 mm x 12.7 mm (5” x 0.39” x 0.5”) o 5 notched and un-notched specimen for each configuration o Drop height of 177.8 mm (7”) o Drop velocity of 1.86m/s (6.1 ft/s) o Impact energy of 5.78 J (4.26 ft-lbf) Impact Tup

Drop Height

Specimen Span

Support

o Typical load vs deflection and energy absorption curves. o Approx strain rate of 13/ sec o Energy absroption • Almost double with 2.5 wt percent reinforcement for both graphite nanoplatelets as well as cloisite nanoclay un-notched specimen.s • Reduced by 50% for notched specimens with 2.5 wt percent reinforced cloisite 30B nanoclay, and 75% for graphite nanoplatelets

Shock Tube Testing 140

o Approx strain rates of 254 mm x 101.6 mm x 9.9 1000/sec and mm (10” x 4” x .39”) sample 1600/ sec for tested at University of Rhode 70 PSI and Island 120 PSI Typical 120 Psi pressure One sample from each respectively profile curve configuration in simply o Energy absorption obtained by supported boundary condition converting pressure to load from Shock tests performed at 70 pressure profile curve, deflection Psi (0.48 MPa) and 120 Psi from real time image, and (0.82 MPa) peak pressure. integrating area under the loaddeflection curve Shock wave velocities of 500 o Samples tested at 120 Psi peak m/s (1640 ft/s) and 600 m/s pressure shattered in pieces while (1968.5 ft/s) no failure occurred for tests at 70 Real time images captured at Psi intervals of 100-150 o Qualitative results show similar microseconds trend at 120 Psi peak pressure as that of low-velocity un-notched Split Hopkinson impact Bar Testing test results 120 100

o

80

(i) u s re P

60 40 20 0

0

2

4

6

8

10

12

14

Time (millisec)

o

o

o

o

Real time deflection image

o Typical energy absorption curves. o Approx. strain rate of 2500/sec and 3500 /sec Typical sample size

0.4

0.050

Sample: DNM00AH-1 Transmission Bar Signal Incident Bar Signal Incident Bar Signal, Volts

0.2

0.025

Incident Compressive Pulse

0

0

-0.2

-0.025

Transmitted compressive pulse -0.4 -0.00050

-0.00025

0

0.00025

-0.050 0.00050

Transmission Bar Signal, Volts

Reflected tensile pulse

o φ 9.9 mm x 4.5 mm (φ 0.39” x 0.18”) samples tested at University of New Orleans o One sample tested from each configuration o Impact velocities of 15 m/s (49.2 ft/s) and 16 m/s (52.5 ft/s)

Time

Future Work oMore specimens to be tested using shock tube and split Hopkinson bar oFinite Element Simulation of shock tube rupture to validate energy absorption.

o Energy absroption • Increased for pure matrix with increase in strain rate. • Increased by 30% with 2.5 wt percent cloisite 30B nanoclay reinforcement for both strain rates. • Increased and than decreased for graphite nanoplatelets at 2500/ sec and showed low energy .than pure matrix for 3500 /sec strain rate.

Acknowledgment

This research is partially supported by ONR Grant # N00014-07-11010, Solid Mechanics Program (Dr. Yapa D.S. Rajapakse, Program Manager) & SERRI/DHS TO # 4000055459.