A manufacturing process for manufacturing mechanical or structured parts or articles comprising a thermoplastic composite material comprising (a) a polymeric thermoplastic (meth)acrylic matrix which is poly methyl methacrylate meaning a methyl methacrylate homopolymer or a copolymer comprising at least 70% by weight of methyl methacrylate and having a weight average molecular weight larger than 100 000g/mol as measured according to according to the method in the description (b) a fibrous material as reinforcement wherein the fibrous material comprises either a fiber with an aspect ratio of the fiber of at least 3000 or the fibrous material has a two dimensional macroscopic structure, said process comprising the following steps: a) impregnating a fibrous substrate with a liquid syrup comprising a monomer or monomers for forming said polymeric thermoplastic (meth)acrylic matrix and an oligomer or a polymer that is a methyl methacrylate homopolymer or copolymer comprising at least 70% by weight of methyl methacrylate, obtained by dissolving said oligomers or polymers in the monomer or monomers, the dynamic viscosity at 25°C of the liquid syrup is between 10 mPa * s and 1000 mPa * s measured with a Rheometer, b) polymerising the liquid syrup impregnating said fibrous substrate, characterized in that the oligomers or polymers in the syrup represent at least 18% by weight of total syrup and characterized in that the composite material comprises at least 40% by weight of fibrous material. (a) a polymeric thermoplastic (meth)acrylic matrix which is poly methyl methacrylate meaning a methyl methacrylate homopolymer or a copolymer comprising at least 70% by weight of methyl methacrylate and having a weight average molecular weight larger than 100 000g/mol as measured according to according to the method in the description (b) a fibrous material as reinforcement wherein the fibrous material comprises either a fiber with an aspect ratio of the fiber of at least 3000 or the fibrous material has a two dimensional macroscopic structure, said process comprising the following steps: a) impregnating a fibrous substrate with a liquid syrup comprising a monomer or monomers for forming said polymeric thermoplastic (meth)acrylic matrix and an oligomer or a polymer that is a methyl methacrylate homopolymer or copolymer comprising at least 70% by weight of methyl methacrylate, obtained by dissolving said oligomers or polymers in the monomer or monomers, the dynamic viscosity at 25°C of the liquid syrup is between 10 mPa * s and 1000 mPa * s measured with a Rheometer, b) polymerising the liquid syrup impregnating said fibrous substrate, characterized in that the oligomers or polymers in the syrup represent at least 18% by weight of total syrup and characterized in that the composite material comprises at least 40% by weight of fibrous material. a) impregnating a fibrous substrate with a liquid syrup comprising a monomer or monomers for forming said polymeric thermoplastic (meth)acrylic matrix and an oligomer or a polymer that is a methyl methacrylate homopolymer or copolymer comprising at least 70% by weight of methyl methacrylate, obtained by dissolving said oligomers or polymers in the monomer or monomers, the dynamic viscosity at 25°C of the liquid syrup is between 10 mPa * s and 1000 mPa * s measured with a Rheometer, b) polymerising the liquid syrup impregnating said fibrous substrate,