Hughes Aircraft Company

Raymond E Kelchner, Jr

Leon B Keller

A polymeric fibrous sheet is provided in the form of a composite of an open matrix of coarse fibers extending throughout the sheet and integrated with co-crystallized, fine fibers spanning the open spaces within the matrix. This non-woven sheet is formed by applying a thin film of polymer solution to the top surface of a substrate undergoing agitation. The substrate can be continuous, such as a belt, agitated by applying oscillatory motion from an acoustic or pneumatic driver to the shafts carrying the cylindrical rollers for the belt. The agitation is at a level sufficient to develop a reciprocating flow field with a velocity gradient sufficient to uncoil and orient the polymer chains in solution and induce the growth of fibers. As the agitated solution cools, a sheet is formed as linear polymer chains crystallize. Residual solvent is removed and the sheet is then dried in the dryer. Sheets with higher fiber content and strength are produced by using substrates containing grooves, especially substrates containing a second set of grooves normal to the first set of grooves, formed by a pattern of raised protrusions. The sheet produced using the patterned substrate contains a network of coarse fibers which roughly replicate the pattern of the grooves.

Non-woven sheet by in-situ fiberization

A polymeric fibrous sheet is provided in the form of a composite of an open matrix of coarse fibers extending throughout the sheet and integrated with cocrystallized, fine fibers spanning the open spaces within the matrix. This non-woven sheet is formed by applying a thin film of polymer solution to the top surface of a substrate undergoing agitation. The substrate can be continuous, such as a belt, agitated by applying oscillatory motion from an acoustic or pneumatic driver to the shafts carrying the cylindrical rollers for the belt. The agitation is at a level sufficient to develop a reciprocating flow field with a velocity gradient sufficient to uncoil and orient the polymer chains in solution and induce the growth of fibers. As the agitated solution cools, a sheet is formed as linear polymer chains crystallize. Residual solvent is removed and the sheet is then dried in the dryer. Sheets with higher fiber content and strength are produced by using substrates containing grooves, especially substrates containing a second set of grooves normal to the first set of grooves, formed by a pattern of raised protrusions. The sheet produced using the patterned substrate contains a network of coarse fibers which roughly replicate the pattern of the grooves.

Composite materials are disclosed which consist of extensible polymer matrices in combination with three-dimensionally structured, interconnected fibrous masses which are formed 'in situ'. These composites exhibit novel mechanical characteristics which are distinctly different from those exhibited by conventional fiber-filled elastomers.

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Los Angeles, CA, United States of America

Raymond E Kelchner, Jr