A liquid (meth)acrylic syrup for impregnating a fibrous substrate, said fibrous substrate consisting of long fibers, said liquid (meth)acrylic syrup comprising:
- a) a (meth)acrylic polymer,
- b) a (meth)acrylic monomer,
- c) 10% by weight to 70% by weight of fillers, based on the total liquid (meth)acrylic syrup, wherein the fillers are chosen from particles with a degree of swelling in the (meth)acrylic monomer of less than 200%, the degree of swelling being defined as the capacity of a particle immersed in a compound to change in volume, and a mean diameter D50 of less than 50 μm, wherein the particles include hollow glass beads, cross-linked PMMA beads, or both, and
- said liquid (meth)acrylic having a dynamic viscosity of between 10 mPa·s and 10,000 mPa·s.