The present disclosure is directed to a composite structure that is generally planar in shape. The composite structure has one or more layers； at least one of the layers includes one or more types of fibers. In one aspect, the present disclosure is directed to a composite structure including a hydrophobic support layer and a hydrophilic reservoir layer. The hydrophilic reservoir layer includes a composition that is liquid at temperatures below 30-35 degrees Celsius and that is a hydrogel at temperatures above 30-35 degrees Celsius. In order to better control the phase change of the composition and, therefore, to insulate the hydrophilic reservoir layer from warmth, the hydrophobic support layer may have a thermal conductivity that is 5 to 30 times less, in watts per meter kelvin, than water.
