Fiber sheets and structures comprising fiber sheets

A fiber sheet comprising:

• fibers having an average fiber length of 0.5-100 mm,
• a binder selected from the group consisting of a polyvinyl alcohol, a polyvinyl acetate dispersion, an ethyl vinyl alcohol dispersion, a polyurethane dispersion, an acrylic latex, a styrene butadiene dispersion, a binder based on finely divided cellulose, a binder based on cellulose a derivative, a biopolymer, and combinations thereof, and
• a foaming agent, and
• wherein 50-99 wt % of the fibers are natural fibers and 1-50 wt % of the fibers are reinforcement fibers selected from the group consisting of a polymer fiber, a mineral fiber, a non-wood natural fiber, a glass-fiber, and combinations thereof,
• and wherein the fiber sheet has a stretch in the range of 3-50%.