Copolymerization of polylactic acid with ductile polymers (to create polymer blends) is one of the starting steps for enhancing the ductility of this biopolymer. You can begin with studying our preliminary work on this direction at: https://www.scientific.net/AMR.530.46 and the references cited therein. The full pdf is also available in my researchgate profile. The major tasks ahead with you are in property analysis, processing techniques, selection of appropriate copolymer, mass percentage of the two/multi polymers and thermo-mechanical-chemical characterization of the blend. Then you can prepare composite with the polymer blend.
Depending on the trimethylene carbonate content, poly(L-lactic acid)-co-(trimethylene-carbonate) -PTMC- exhibits much lower Tg than pristine PLA. Therefore, the incorporation of certain PTMC quantites in the PLA composites' recipie would reduce their brittleness.