Owing to the outstanding properties of nano-Al 2 O 3 particles have incited material researchers to have a promising invasion in the field of fibrous polymeric composites. There is an uncertainty of nano-Al 2 O 3 /polymer interfacial stability at high temperature engineering applications. Current investigations explicate the effects of nano-Al 2 O 3 content on the mechanical behavior of glass/epoxy (GE) composites at various in-situ elevated temperatures. The flexural properties and viscoelastic behavior of the composites have been investigated and evaluated. The Weibull design parameters were analysed as a function of nano-Al 2 O 3 content and different test temperatures. Scanning electron microscopy analyses were carried out to understand various interfacial strengthening mechanism and micro-mechanism failures. These results indicated that incorporation of 0.1 wt% of nano-Al 2 O 3 in GE composites at room temperature could be considered an optimal value in flexural strength enhancement. The fracture surfaces demonstrated a combination of fiber pullout, interfacial debonding, matrix drainage and fiber imprints failure morphologies. Weibull analyses responded a reasonable agreement with the experimental results. © 2019 Elsevier Ltd