Abstract: A method of vacuum moulding a composite material in which laid-up prepregs uncured resin and reinforcing filaments are placed on a heated former and covered with a sheet of a microporous film material a breather material and an impermeable membrane. The volume enclosed by the membrane is evacuated and the temperature of the mould increased to firstly outgas the resin and mould the prepregs to the shape of the former and finally cure the resin. The arrangement ensures excellent access of the prepregs to the vacuum during the moulding operation, thereby in turn ensuring that the resultant moulded article has very low porosity as a result of gas or vapor inclusions or is porosity-free.

Abstract: A method of manufacturing a damped resonator acoustical panel in which a porous acoustical damping fabric and a resin impregnated open weave fabric are laid up and subjected to moulding by the application of heat and pressure thereto to cause a portion of the resin from the open weave fabric to impregnate the abutting portions of the acoustical damping fabric and bond the fabrics together. A film of an adhesive is then applied to the open weave fabric and heated by a hot gas stream until it reticulates. The bonded fabrics are then bonded to the edges of an open honeycomb core by means of the reticulated adhesive. A solid sheet is bonded to the other side of the honeycomb core in order to close the cells thereof.