Process for manufacturing thermoplastic polymer composite parts, and object obtained by said process

A process for manufacturing an object made of a thermoplastic polymer composite from at least two parts made of (meth)acrylic thermoplastic polymer composite, said (meth)acrylic thermoplastic polymer composite comprising a fibrous reinforcement of long fibers having an aspect ratio of at least 7500 or continuous fibers and a thermoplastic polymer matrix, said process comprising the steps of:

• impregnation of a fibrous reinforcement with a liquid (meth)acrylic composition,
• polymerization of the liquid (meth)acrylic composition to manufacture the at least two parts made of (meth)acrylic thermoplastic polymer composite comprising the fibrous reinforcement and a (meth)acrylic thermoplastic polymer matrix,
• deposition of a layer of (meth)acrylic thermoplastic polymer at least at an assembly interface zone,
• arranging the two parts made of thermoplastic polymer composite adjacent or overlapping at said assembly interface zone, and
• heating to melt the thermoplastic polymer matrix at said assembly interface zone, so as to form an object made of thermoplastic polymer composite comprising a welded interface,
• wherein the thermoplastic polymer matrix is melted by a technique selected from the group consisting of:
• ultrasonic welding, induction welding, resistance wire welding, friction stir welding, laser welding, and heating by infrared or ultraviolet radiation, wherein at least one of the two parts made of thermoplastic polymer composite comprises the layer of (meth)acrylic thermoplastic polymer at least 0.5 mm thick on a surface intended to be welded, and wherein the (meth)acrylic thermoplastic polymer of the (meth)acrylic thermoplastic polymer composite and the layer of (meth)acrylic thermoplastic polymer has a glass transition temperature between 50° C. and 140° C. and the (meth)acrylic thermoplastic polymer or a portion of the (meth)acrylic thermoplastic polymer of the (meth)acrylic thermoplastic polymer composite and the layer of (meth)acrylic thermoplastic polymer has a melt flow index less than 20 g/10 min according to the standard ISO 1133.