This International Standard specifies a method for the determination of the mass per unit area and five methods (Method A to Method E) for the determination of the fibre mass per unit area of moulding compounds and prepregs. Method A: Extraction by soxhlet Method B: Extraction by immersion in solvent in a beaker Method C: Decomposition by loss ignition Method D: Extraction by wet combustion Method E: Method by calculation This International Standard is applicable to the following types of material: moulding compound and preimpregnated unidirectional sheet, tape, fabric and mats. prepregs in which any type of reinforcement (aramid, carbon, glass, etc.) and any type of matrix (thermosetting or thermoplastic) has been used. Typically, reinforcement fibres are coated with sizing or finishes. These normally dissolve with the resin and are, therefore, included in the resin content. This International Standard is not applicable to the following types of prepregs: these containing reinforcements which are soluble (or partly soluble) in the solvents used to dissolve the resin.