The work aims at the experimental investigation and theoretical modeling of the physical phenomena responsible for thermal bonding of polymer fibers in nonwovens and their effect on such mechanical properties as the nonwoven stiffness, the yield stress, the stress at failure, toughness, and the entire stress-strain curve. In the experiments two types of nonwovens were explored: Polybutylene Terephthalate (PBT) nonwoven and Polybutylene Terephthalate (PBT)/Polyethylene (PE) (80/20) nonwoven. Special attention was paid to the effect of the bonding pattern (e.g. circular or rhombic) on the nonwoven failure patterns in stretching. It was shown that failure happens at the periphery of stiffened bonds. A theory of this phenomenon is given which predicted tensile stress concentration up to 140% of the applied tensile stress in that area, which was responsible for the failure modes observed experimentally. (C) 2018 Elsevier Ltd. All rights reserved.