Flexible bags having enhanced capacity and enhanced stability in use

A flexible bag comprising at least one sheet of flexible sheet material assembled to form a semi-enclosed container having an opening defined by a periphery, said opening defining an opening plane, said bag having an upper region adjacent to said opening and a lower region below said upper region, said upper region having an elongation axis perpendicular to said opening plane which permits said upper region to expand in response to an externally-applied force upon said bag, said lower region having an elongation axis parallel to said opening plane which permits said lower region to expand in response to forces exerted by contents within said bag to provide an increase in volume of said bag, wherein said sheet material exhibits an elastic-like behavior along at least one axis, said sheet material comprising:

• at least a first region and a second region, said first region and said second region being comprised of the same material composition and each having an untensioned projected pathlength, said first region undergoing a substantially molecular-level deformation and said second region initially undergoing a substantially geometric deformation when said web material is subjected to an applied elonation in a direction substantially parallel to said axis in response to an externally-applied force upon said flexible storage bag when formed into a closed container, said first region and said second region substantially returning to their untensioned projected pathlength when said applied elongation is released.