Cooling of fibrous sheet for composite structure during machining

An apparatus for machining a fibrous sheet 10 for a composite structure comprises a support for the sheet 12a, 12b, a machining tool 30 movable relative to the support and a cooling system 20, 34 for cooling the sheet. A method of machining the sheet comprising a resin matrix comprises supporting the sheet for machining and cooling at least part of the sheet to maintain the temperature of the matrix below its glass transition temperature during machining. The sheet may be pre-cooled before machining or cooled during machining. Preferably a cooling fluid 18 may be applied to the sheet at a location that moves to correspond with the region of the sheet being machined. The cooling means may comprise sandwiching the sheet between opposed cooled surfaces 12a, 12b, cooling the matrix to at or below zero degrees Celsius. The machining tool may have a cutting or grinding action preferably to effect tapering an edge of the sheet. The sheet may be incorporated into a composite structure with the tapered edge lying beside at least one other fibrous reinforcement sheet.