A female die part has an upwardly opening die cavity for receiving a male die plunger, a supporting surface around the cavity for a porous batt of fibrous reinforcing material overlying the cavity, and a first shearing edge defining the periphery of the opening for the cavity. Peripheral portions of the batt are clamped to the supporting surface, whereupon the die plunger presses portions of the batt into a mold formed between the male plunger and the sidewalls of the cavity to completely fill the mold. A cutter having a second shearing edge cooperates with the first shearing edge to shear peripheral portions of the batt from the portions overlying the die cavity. The shearing edges in cooperation with the die plunger seal the mold to enable injection of reactive chemicals that impregnate the porous batt within the mold.