Abstract: A filled hollow fibre composite material is made by laying up a plurality of prepreg plies (1) of hollow fibre composite material and non-stick film material (2) one on top of another with the non-stick film material (2) interleaving successive plies (1) at selected areas thereof. The laid up interleaved plies are treated to resin bond the ply areas (3) not interleaved with the non-stick film material and leave the interleaved areas (4) unbonded. The so formed laminate is treated at edge regions to expose open unfilled hollow fibre ends (5, 6) and the plies in the unbonded interleaved areas (4) are separated at the non-stick film material (2) to provide access to the open hollow fibre ends (7) in each ply for the introduction of a film material into the hollow fibres through the open hollow fibre ends (7) in one or more of the separated plies (1) to form a filled hollow fibre composite material.

Abstract: The diffusion bonding of aluminum and aluminum alloys presents problems because, when left exposed to the atmosphere even for a short time, they acquire an extremely tenacious surface oxide layer that inhibits or prevents satisfactory diffusion bonding. Unlike titanium, this oxide layer is not absorbed at diffusion bonding temperatures. The present invention comprises a method of reducing oxidation of a surface of aluminum or aluminum alloy by causing a nitride film to form on the surface. This film is believed to prevent oxidation of the aluminum or aluminum alloy, but to be absorbable into it at diffusion bonding temperatures. In the preferred embodiment shown in FIG. 1, the nitride film is applied to the piece of aluminum or aluminum alloy (10) in a vacuum chamber (4) by sputtering with nitrogen ions, or by heating the piece (10) in a nitrogen gas atmosphere.