Sheet molding compound having improved characteristics
View Patent ↗A composite part made from a sheet molding compound is disclosed as having improved characteristics over traditional sheet molding compound composite parts. The fibrous material is introduced as a veil layer adjacent a paste layer, the veil flows well during the molding process. The improved flow and surface characteristics of a composite part are attributed to the elongation of the veil during molding and to the improved filling capabilities.
1. A sheet molding composite sheet for use in structural reinforced compression molded composite parts, the sheet comprising in an uncompacted form between a pair of outer film layers:
a first layer of resin paste applied to one of the pair of outer film layers;
a second layer of resin paste applied to the other of the pair of outer film layers;
n layers of nonwoven discrete filaments or reinforcement fibers, wherein the filaments or fibers do not melt when exposed to a temperature of 200 degrees C. for twenty seconds; and
(n−1) layers of resin paste volumetrically applied to between each of said n layers of reinforcement fibers using a volumetric paste extrusion device so as to provide alternating layers of nonwoven discrete filaments or reinforcement fibers and resin paste, wherein n is at least 2.
2. The sheet molding composite sheet of claim 1 , wherein at least one of said (n−1) layers of resin paste is a bulk molding compound layer.
3. The sheet molding composite sheet of claim 2 , wherein said bulk molding compound layer is volumetrically applied using a volumetric paste extrusion device having a bulk molding volumetric slit extrusion die.
4. The sheet molding composite sheet of claim 2 , wherein said bulk molding compound layer contains low-density fillers.
5. The sheet molding composite sheet of claim 2 , wherein said bulk molding compound layer contains recycled materials of various granulometry and morphology.
6. The sheet molding composite sheet of claim 1 , wherein said first layer of resin paste is volumetrically applied using a volumetric paste extrusion device.
7. The sheet molding composite sheet of claim 1 wherein said first layer and said second layer are volumetrically applied using a volumetric paste extrusion device.
8. The sheet molding composite sheet of claim 1 , further comprising introducing at least one layer of a preformed veil in place of a respective one of said layers of reinforcement fibers.
9. The sheet molding composite sheet of claim 1 , wherein said veil comprises a binder substantially soluble in said paste.
10. A sheet molding composite sheet for use in structural reinforced compression molded composite parts, the sheet comprising in an uncompacted form between a pair of outer film layers:
a first layer of resin paste applied to one of the pair of outer film layers;
a second layer of resin paste applied to the other of the pair of outer film layers;
n layers of irregularly shaped reinforcement filaments or fibers; and
(n−1) layers of resin paste volumetrically applied to between each of said n layers of reinforcement fibers using a volumetric paste extrusion device so as to privede alternating layer of nonwoven discrete filaments or reinforcement fibers and resin paste, wherein n is at least 2.
11. The sheet of claim 1 wherein said fibers or filaments comprise glass fibers or filaments.