Composite materials display many advantages over traditional materials, whether in terms of lightness or mechanical and chemical resistance. The development of composites meets the requirements of industrial markets for applications in the fields of transport and construction, as well as sports and leisure. In a context of sustainable development, a growing number of works relate to the production of composites with bio-based matrices [1] including polylactide (PLA), which has become a major actor in the market which could in the long term serve as an alternative to petroleum-based polyolefins.[2]Among the various composites production processes, Resin Transfer Molding (RTM) is a specific process which relies on the injection, into a mold containing fibers, of a monomer and a catalyst in order to carry out the polymerization of the matrix in situ. The major advantage over conventional melt processes is the possibility of reaching a high amount of fibers while improving their wetting by the matrix. While a wide selection of thermosetting matrix resins are available on the market for RTM process, there are only a few commercial resins for thermoplastic matrices.[3]Although work has been carried out in RTM with -caprolactone,[4] composites with a polylactide matrix via this process had never been described, due to the lock linked to the solid state of the monomer at room temperature (initiation of polymerization before injection into the mold during the melting phase in the presence of the catalyst). Recent work carried out at UMET made it possible to obtain the first prototypes of PLLA/glass fiber composites with different reinforcement rates.[5] We present here current work aimed at strengthening the mechanical properties of the PLLA matrix, and in particular its elongation at break, by producing a novel family of composites with PLLA-based copolymer matrices, by copolymerization of L-LA with other cyclic esters.References[1] “Green Composites: Polymer Composites and the Environment”. C. Baillie, CRC Press, 2004. [2] M. Jamshidian, E. A. Tehrany, M. Imran, M. Jacquot, S. Desobry, Compr. Rev. Food. Sci. F., 2010, 9, 552-571.[3] (a) K. Van Rijswijk, H.E.N. Bersee. Compos. Part A Appl. S., 2007, 38, 666-681. (b) B. Campos, S. Bourbigot, G. Fontaine, F. Bonnet, Polym. Compos. under press. [4] T. J. Corden, I. A. Jones, C. D. Rudd, P. Christian, S. Downes. Compos Part A. Appl Sci Manuf. 1999, 30, 737-746.[5] E. Louisy, F. Samyn, S. Bourbigot, G. Fontaine, F. Bonnet. Polymers, 2019, 11, 339-347.