Discusses the mechanical properties of polymeric materials and their various reactions to moisture content and temperature. Specifically, the interfiber forces in dry and immersed assemblies and drained and drying assemblies are explained. The changes in fibrous assemblies are attributed to both intrinsic fiber behavior and complex interaction between fibers in theassembly. It is also determined that the presence of capillary water and surface tension forces dominate the behavior of the assembly. These statements are verified through experimentation. In conclusion, the application of the findings in both textile and paper manufacturing are briefly given. -- AATA