Study On The Dynamic Response And Cracks Propagation Of Laminated Glass Subjected To Blast Load

As a new composite structure, laminated glass(LG) is made up of glass andglue layer under high temperature and high pressure, which has the advantage ofbetter transmittance, no color-fading, fatigue resistance, weathering resistanceand convenience to install. In recent years, LG has been widely used as the mainsafety-protecting device in the areas of building industry, auto industry,aerospace, ship-manufacture and so on. However, with the rampant developmentof terrorisms, the big-iconic architecture, autos, subway and ships are all in thescope of the attack. Now the research on the blast resistance of LG is domesticand international research hot point due to the great casualties and enormousproperty loss caused by the terrorist attacks.Based on the research results of LG blast resistance published in recentyears, we investigated the dynamic response and cracks propagation laws of LGsubjected to blast loads by experimental test, numerical simulation andtheoretical analysis as follows.:(1) The blast experiments on LG wereperformed to obtain its dynamic response. The dynamic mechanic behaviors of LG under different explosion circumstances were analyzed by changing thesingle glass layer thickness, the equivalent explosion mass and the detonationdistance. The finite element(FE) models of LG blast experiments have been builtby the software LS-DYNA. The ALE element algorithm and FSI fluid-solidcoupling contact are applied to simulate the interaction between impact waveand LG, the simulation results are compared and validated with the experiments;(2) The researches of LG crack propagation laws under blast loads, which areimplemented using the*LOAD_BLAST, have been performed on LS-DYNA.The process of generation and propagation of cracks are described and thefailure mechanisms of LG under different loads are compared in this model,which are meshed into tetrahedron and hexahedron.(3) Based on the classicalthin-plate large and small deflection theories and laminated plate stiffness theory,the center deflections of LG, which is under uniformly distributed loads withfour edges simply supported, have been studied by theoretical analysis. Thedeflections deduced from theoretical analysis are compared and validated withFEA results in literature [14] and the center deflections of LG with symmetricalthicknesses are investigated by theoretical analysis and FEA.Through the research, three results have been obtained as follows:(1) Interms of the blast experiment:(a) As the main bearing structure, the thickness ofglass had a big influence on the blast resistance of LG, what meant by this wasthe blast resistance of LG improved significantly by the increase of thickness ofinternal and external glass;(b) the equivalent explosion mass and detonation distance were the crucial factors of the blast overpressure values.(c) Byanalyzing the strain of LG, the compressive stress wave reflected to tensile wavethrough free-edge side and the internal glass was suffered tension force. Thestrain gages suffered the tensile strain and the compressive strain was caused bythe vibration of glass and the effect of experimental environment.(2) Thesimulation results of LG cracks propagation show:(a) The increasing of theexplosion mass could cause more radial cracks, which propagate from the centerto the boundary in radial shape under the same detonation distance. Thecircumferential cracks are not obvious when the explosion mass is small, andfew cracks occur just at the center if it appeared;(b) The number of LG cracksdecrease with increasing the detonation distance by using the same explosionmass. The radial cracks take a great proportion and the circumferential cracksconcentrate at the center of glass;(c) At20cm detonation distance, LG just hasthe radial cracks with15g explosion mass, the circumferential cracks occur with30g explosion mass and, the number of radial and circumferential crackssignificantly increase with45g explosion mass.(3) The deflection formulas atthe center of LG with four-edge simply supported under the uniform loads arededuced based on the classical thin-plate large and small deflection theory andlaminated plate stiffness theory. The deflection curves are compared with theliterature [14] to verify the reliability of the deflection formulas. The theoreticalanalysis and FEA methods are used to simulate the deflections of more LGmodels under the pressureP020KPa， t m5msfor the verification of the deflection theory.