Quantitative and consistent tests for interlayer adhesion in laminated glass
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The use of the double cleavage drilled compression (DCDC) for determining the toughness of glass/PVB interfaces has been examined. Experiments were conducted on two different types of samples: low and high adhesion. Stress and fracture analysis was conducted using the finite element method. The numerical analysis was first validated against simple strength of materials analyses and the measured load deflection response. The numerical analysis then provided the variation of stress intensity factors, energy release rate and fracture mode-mix with crack length for the extraction of toughness. Further microscopic analysis of the fracture surfaces elaborated different scenarios to describe the observed fracture mechanisms. At least partial delamination was observed, followed by finger shaped interface cracking and/or kinking. In addition, glass cracks branched to the interface and provoked partial interface delamination. In all cases, cracks were considered to be close enough to the interface to be considered as such. Values for the interfacial fracture toughness were extracted and found to be 160 J/m² and 230 J/m² for the low and high adhesion specimens, respectively.