Method for producing a dry preform produced by knitting, method for manufacturing a product made of composite materials from said preform

A method for producing a product made of composite materials, comprising:

• using a dry preform obtained by a sequence comprising the following steps:
• simultaneous weft/wale knitting of at least one stitch thread and at least one unidirectional reinforcement thread, at least one of said materials being thermoplastic and having a melting point lower than the melting point of at least one other material, referred to as reinforcement material, and
• creating a three-dimensional knit that constitutes a dry preform in a shape of a product that is to be obtained from the dry preform
• putting said preform in place on a model having the profile of the product that is to be created;
• heating to at least the lowest melting point so as to impregnate and/or coat the at least one other thread made of at least one other material with the at least one thermoplastic material transformed by melting;
• and
• cooling the product obtained in this manner,
• wherein the method for producing a product made of composite materials does not include a step of adding resin.