Aggregate-based mandrels for composite part production and composite part production methods

Abstract

A method for forming a composite structure, using a mandrel that is later removed from the composite structure, involves production of a mandrel by depositing a particulate mixture, including an aggregate and a binder, into a mold and removing the mandrel from the mold. The mandrel may be treated while still in the mold by heating, curing with an agent, microwave energy, or by some combination thereof. Once finished, the mandrel can be used in manufacturing polymer and/or composite components. The mandrel can also include materials that can be easily removed from the finished composite structure by water, shakeout, chemically dissolving, or by some combination thereof. The mandrel can be a self-expanding mandrel, and can be used in a process or system for the manufacture of composite structures.

What is claimed is: 
     
         1 . A system for manufacturing a composite structure having external dimensions, comprising
 a tool having internal dimensions that match the external dimensions of the composite structure,   a self-expanding water-soluble mandrel comprising a water-soluble binder and an expandable material, and   a composite material between the mandrel and the tool.   
     
     
         2 . The system of  claim 1 , wherein the composite material comprises a thermosetting or thermoplastic material. 
     
     
         3 . The system of  claim 1 , wherein the expandable material is an expandable polymer particle or an expandable graphite 
     
     
         4 . The system of  claim 1  wherein the water soluble binder comprises an organic polymer. 
     
     
         5 . The mandrel of  claim 1 , wherein the expandable material comprises a material that expands when subjected to heat, light, energy or chemical reaction. 
     
     
         6 . The mandrel of  claim 1 , wherein the expandable material expands under thermal conditions between about 150° F. and about 700° F. 
     
     
         7 . The mandrel of  claim 1 , wherein the expandable material comprises an expandable polymer particle that expands between about 200° F. and about 350° F. 
     
     
         8 . The mandrel of  claim 1 , wherein the expandable material comprises an expandable graphite that expands between about 350° F. and about 650° F. 
     
     
         9 . The system of  claim 1 , wherein the self-expanding mandrel applies pressure to a composite material applied on the mandrel's surface.