Composite material and synthetic sleeper using the composite material

A composite material comprising:

• a core layer comprising a particulate filler having an average particle size of 0.5 mm or more and synthetic resin and containing the filler having a weight 0.7 times or more the product of volume of the core layer and bulk density of the filler;
• and
• a surface layer comprising a thermosetting resin including lightweight filler reinforced by long fibers extending parallel in a longitudinal direction thereof, said long fibers being present in an amount of 5 volume % to 40 volume %;
• and the surface layer being laminated on the core layer to cover at least one surface of the core layer with respect to a thickness direction thereof.

A composite material comprising a core layer comprising synthetic resin as a main component and a surface layer comprising foam thermosetting resin reinforced by long fibers extending parallel in a longitudinal direction thereof or elastic synthetic resin reinforced by long fibers extending parallel in a longitudinal direction thereof and laminated on the core layer to cover both surfaces of the core layer with respect to a thickness direction thereof, wherein the core layer and the surface layer have the relation that satisfies the equations of CSa≧½×CSb, Ea<Eb, and ESa≧½×ESb (where CSa represents yield strain in compression of the core layer;

• CSb represents yield strain in compression of the surface layer;
• Ea represents a tension elasticity modulus of the core layer;
• Eb represents a tension elasticity modulus of the surface layer;
• ESa represents yield strain in tension of the core layer;
• and ESb represents yield strain in tension of the surface layer).