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A Systematic Experimental Approach for Damage Quantification in Sandwich Structures under Low-heat Fire Induced Damage



The amount of damage propagating into the core due to excessive heat or lowintensity fire will initiate several interacting failure modes in sandwich structures. Using several characterization techniques, this paper presents a systematic experimental approach to demonstrate the effect of low heat-intensity damage in GFRP foamsandwich structures. GFRP composite sandwich panels were fabricated using the Vacuum-Assisted Resin Transfer Molding (VARTM) process. The laminate stacking sequence included four plies on each side of the PVC foam core (Divinycell® Inc.). Each ply was constructed of knitted E-glass [+45/−45/Mat; 883g/m2] with mat facing the core. Heat was induced by localized heat fluxes (10 kW/m2) using the cone calorimeter test. The baseline sample experienced global buckling, whereas samples exposed to one sided heat exposure exhibited skin wrinkling and core shear instability. This shift in failure modes in the presence of damage must be taken into account in the design process. Techniques including the 3D optical profilometer, Dynamical Mechanical Analysis (DMA), and X-Ray CT scan, captured the morphology of the damage, the thru-thethickness thermal decomposition of the core, and the extent of damage in the foam core, respectively. Detailed mechanical tests were also performed to quantify the degraded and residual mechanical properties of all constituent materials constructing the sandwich panel. The developed methodology may well serve to predict the edge wise compression behavior and failure mechanisms of post-fire/heat damaged sandwich structures. This approach could be implemented in a material characterization code/software to support the hierarchical modeling from the macro-scale to the structural scale of deployable and in-service sandwich structures


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