MODULAR COMPOSITE SANDWICH STRUCTURES FOR THERMAL AND STRUCTURAL RETROFITTING OF EXISTING BUILDINGS

Around 40% of global energy consumption and 30% of worldwide carbon dioxide (CO2) emissions are attributed to buildings. Most of this consumption is dedicated to ensuring thermal comfort. The goal of this research was to develop and field validate retrofit solutions to improve the energy efficiency of buildings. Exterior cladding panels were designed and tested to ensure adequate thermal and structural performance. Sandwich panels (glass fibers reinforced polymer (GFRP) skins and polymeric foam cores) were fabricated using the vacuum assisted resin transfer molding (VARTM) process. Extruded polystyrene (XPS) and polyurethane (PU) foams were compared as core materials through a series of thermal and mechanical tests. Thermal resistances of 3.62-4.66 h.ft2.°F/Btu (0.64-0.82 K.m2/W) per inch were obtained for sandwich structures. XPS samples were 26% lighter, 24%-40% stronger, and 16%-28% more brittle than PU in quasi-static loading configurations. PU absorbed 11% more energy than XPS in a low-velocity impact (LVI) test. Flatwise tensile test showed that the bonding strength between XPS and GFRP was 47% higher than PU foam. Consequently, XPS was chosen as core material and further tests were conducted accordingly. Tensile testing performed on the GFRP material resulted in a 3,191 ksi (22 GPa) elastic modulus, 42,786 psi (295 MPa) tensile strength, and 0.165 Poisson’s ration. To predict the wind loads according to the American Society of Civil Engineers (ASCE) building standard, flexural tests were conducted on a 4 x 8 ft2 (121.92 x 243.84 cm2) sandwich panel. FEA simulations were also developed to accurately predict the behavior of the retrofit panels based on actual dimensions and connections. Less than 4% variation was noted between experimental and numerical data. The deflections were within the allowable limits set by the International Building Code (IBC). The panels were supposed to be used as an exterior application; therefore, it was important to understand the environmental effects. Discoloration of the GFRP skin due to v ultraviolet (UV) and moisture exposure was observed. Ceramic coating was applied to eliminate the discoloration effect. A fire simulation (ASTM E84) was conducted on a 2 x 24 ft2 (60.96 x 731.52 cm2) panel to obtain surface burning characteristics.