FACULTY OF ENGINEERING & ARCHITECTURE Digital Image Correlation Technique Applied to Laminated Glass Plates Under Free Air Blast Loading Sam Van Dam 1, Joren Pelfrene 1 & Wim Van Paepegem 1 Bachir Belkassem 2 & David Lecompte 2 1 Materials Science and Engineering, Ghent University 2 Civil Engineering & Materials, Royal Military Academy, Brussels DYMAT 21 st Technical meeting, London, UK, 18-20 November 2013 Children's Hospital of Philadelphia, courtesy: DuPont
Outline... Introduction Experimental setup Instrumentation Post-processing & Results DIC Conclusions 2
Introduction... Increased use laminated glass Wingard Design software ASTM Standards Witness panel Limited instrumentation Courtesy Graham A-RES Architectural Architecture Products 3
Introduction... Increase knowledge mechanical response Widely instrumented tests High dynamic loading Digital Image Correlation Finite Element Analysis Validated numerical framework 4
Experimental setup... Laboratory of Analysis of Explosion Effects (LAEE) RMA Steel mounting frame Specimen size 0.4 by 0.4 m Clamping ring, felt 2 high speed camera s Instrumentation 5
Blast setup... Composition C4 Imperfect spherical shape Detonator Type M75, 1g TNT eq. Light intensity trigger Blast pencil ConWep software 6
Digital Image Correlation setup... 2 Photron Fastcam SA5 25.000 fps Shutter 1/40.000 s 512 x 512 pixels 4 light spots Correlated Solutions VIC 3D 7
Instrumentation... Laser doppler vibrometer High shock accelerometer Strain gauges (Blast pencil) (Pressure sensors) 8
Specimens... Laminated glass 400 x 400 mm t glass 4 mm nominal t PVB 0.76 mm t PVB 0.38 mm BLACK 9
Specimens... Speckle pattern Optimized 512 x 512 pixels Silk-screen print 10
Results... 11
Incident pressure [kpa] Results Blast pencils... Reflections due to nearby wall and floor 600 500 400 300 200 100 0-100 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 Time [ms] 12
Incident pressure [kpa] Results Blast pencils... Shockwave reaches cameras after ~7 ms Loss of calibration 175 undisturbed images 6 4 2 0-2 -4 0 2 4 6 8 10 12 Time [ms] 13
Results Blast pencils... Reflection due to curvature glass 14
Displacement [mm] Results DIC... Elastic response reproducible Large scatter afterwards 50 40 30 20 10 0-10 -20-30 Centre displacement, 30 gr - 30 cm 0 3 6 9 12 15 Time [ms] 15
Results DIC... 16
Results DIC... ε 1 ε 2 Principal strains 17
Results DIC... Concurrent with visually observed crack patterns 18
Results DIC... Concurrent with visually observed crack patterns 19
Results DIC... Crack opening hardly visible Correlation software correlates over cracks Strains too large for glass Future test campaign with smaller speckle size Limited view specimen 20
Conclusions... Widely instrumented test setup Large scatter due to brittle material glass Comparison different parameters made difficult Numerical validation & optimisation of blast resistance laminated glass 21
Thank you for your attention! Any questions, remarks? SAM VAN DAM EA10 Materials Science and Engineering Ghent University, Belgium Sam.VanDam@UGent.be 22