Method for preparing a composite high strength to weight structure having shell and sleeved core

Claim 1

A method of producing a structural member of high strength to weight ratio comprising inserting an elongated core strip comprising a foamable resin composition within a seamless sleeve made of a thin, flexible cellulosic film, arranging within a mold cavity an outer shell comprising at least one layer of unidirectionally oriented resin-coated graphite fibers in sheet foam and said elongated core within said sleeve with said shell surrounding said core and sleeve, sealing said mold cavity, activating said foamable resin composition to cause expansion thereof and generate pressure within said mold cavity pressing said core within said sleeve against said shell and thereby providing intimate bonding of said core to said shell, and thereafter removing said core and said shell from said mold cavity as an integral composite structure.

Claim 2

A method of producing a structural member of high strength to weight ratio comprising inserting an elongated core strip comprising a foamable resin composition within a seamless sleeve made of a thin, flexible cellulosic film, arranging within a mold cavity an outer shell comprising at least one layer of unidirectionally oriented resin-coated graphite fibers in sheet foam and said elongated core within said sleeve with said shell surrounding said core and sleeve, sealing said mold cavity, activating said foamable resin composition to cause expansion thereof and generate pressure within said mold cavity pressing said core within said sleeve against said shell and thereby providing intimate bonding of said core to said shell, and thereafter removing said core and said shell from said mold cavity as an integral composite structure.

Claim 8

A method of producing a tennis racket frame of high strength to weight ratio comprising providing a mold cavity shaped in the form of a tennis racket frame having a handle with a grip at one end and a head of ellipsoid shape attached to the other end, the handle grip of said mold cavity having two substantially parallel cavity portions corresponding to two sides of said handle, forming an elongted core strip comprising a foamable resin composition, inserting said core strip into a seamless sleeve made of a thin, flexible cellulosic film which sleeve is of greater cross-sectional area than said core strip, wrapping said core strip within said sleeve with a plurality of layers of unidirectionally oriented resin-coated graphite fibers, at least one of said layers having its fibers oriented in a direction different from the direction of orientation of the fibers in at least one other of said layers, arranging said wrapped core within said mold cavity with both ends of said wrapped core at the grip end of said mold, said wrapped core extending from one of its ends at the grip end of said mold cavity, up one of said substantially parallel cavity portions in the handle portion of said mold cavity, around a major portion of the head portion of said mold cavity and down the other substantially parallel cavity portion in the handle portion of said mold cavity to terminate at the grip end of said mold cavity, thereafter sealing said mold cavity, heating said foamable resin composition to cause expansion thereof and generate pressure within said mold cavity pressing said core against said layers of graphite fibers and thereby provide intimate bonding of said core to said layers, and thereafter removing said expanded wrapped core as an integral composite tennis racket frame.

Claim 9

A method of producing a tennis racket frame of high strength to weight ratio comprising providing a mold cavity shaped in the form of a tennis racket frame having a handle with a grip at one end and a head of ellipsoid shape attached to the other end, the handle grip of said mold cavity having two substantially parallel cavity portions corresponding to two sides of said handle, forming an elongted core strip comprising a foamable resin composition, inserting said core strip into a seamless sleeve made of a thin, flexible cellulosic film which sleeve is of greater cross-sectional area than said core strip, wrapping said core strip within said sleeve with a plurality of layers of unidirectionally oriented resin-coated graphite fibers, at least one of said layers having its fibers oriented in a direction different from the direction of orientation of the fibers in at least one other of said layers, arranging said wrapped core within said mold cavity with both ends of said wrapped core at the grip end of said mold, said wrapped core extending from one of its ends at the grip end of said mold cavity, up one of said substantially parallel cavity portions in the handle portion of said mold cavity, around a major portion of the head portion of said mold cavity and down the other substantially parallel cavity portion in the handle portion of said mold cavity to terminate at the grip end of said mold cavity, thereafter sealing said mold cavity, heating said foamable resin composition to cause expansion thereof and generate pressure within said mold cavity pressing said core against said layers of graphite fibers and thereby provide intimate bonding of said core to said layers, and thereafter removing said expanded wrapped core as an integral composite tennis racket frame.