System and method for manufacturing monolithic structures using expanding internal tools

1. A method of manufacturing a composite article, comprising;

providing an outer mold line (OML) tool having an OML tool surface;

loading an inner mold line (IL) tool within the OML tool encapsulating the IML tool, the IML tool having an IML tool surface having a hollow internal shell and a layer of expandable material on at least a portion of an exterior of the hollow internal shell;

providing a composite assembly between the OML tool surface and the IML tool surface, the OML tool having a gas flow channel extending from the OML tool surface to an exterior of the OML tool;

applying a vacuum bag over a portion of the OML tool at a location of the gas flow channel; drawing a vacuum on the vacuum bag;

heating the layer of expandable material to cause expansion thereof,

drawing at least one of air, gas, and volatiles through the gas flow channel from the tool interior to the exterior of the OML tool using the vacuum drawn on the vacuum bag;

and applying, using the IML tool, an internal compaction pressure on the composite assembly against the OML tool surface during the expansion of the layer of expandable material.

2. The method of claim 1 , further comprising:

positioning an internal component of the composite assembly between a pair of IML tools; and

applying the internal compaction pressure to the internal component positioned between the IML tools during expansion of the expandable material.

3. The method of claim 1 , wherein the step of providing a composite assembly between the OML tool surface and the IML, tool surface includes:

applying a composite layup skin to one or more IML, tool surfaces prior to loading the composite assembly and the IML tool into the OML tool.

4. The method of claim 1 , wherein the step of loading the IML tool within the OML tool comprises:

indexing the IML tool to a locating feature included with the OML tool.

5. The method of claim 1 , wherein the step of loading the composite assembly in the OML tool comprises:

indexing the composite assembly to a locating feature included with at least one of the OML tool and the IML tool.

6. The method of claim 1 , further comprising the steps of:

venting a tool interior of the OML tool to an exterior thereof.

7. The method of claim 1 , further comprising the step of:

curing the composite assembly to form a unitized, monolithic composite article.

8. The method of claim 7 , further comprising the steps of:

applying a solvent to the IML tool;

solubilizing the expandable material; and

removing solubilized expandable material from the composite article.

9. The method of claim 1 , further comprising the step of:

applying a polymer layer to the IML tool surface prior to loading the IML tool inside the OML tool.

10. The method of claim 1 , wherein the step of providing the IML tool comprises at least one of the following:

curing a material mixture within a mold of the IML tool;

curing a material mixture within the OML tool having inserts sized and configured to substantially duplicate a shape of the composite assembly; and

three-dimensional printing the IML tool based upon a computer aided design (CAD) model of the IML tool.

11. The method of claim 1 , wherein the step of applying the vacuum bag includes:

including a breather layer underneath the vacuum bag to provide a continuous path for at least one of the air, gas, and volatiles.

12. The method of claim 8 , wherein:

the solvent comprises one of water and a polar solvent.

13. The method of claim 1 , further comprising the step of:

applying heat to the composite assembly when applying the internal compaction pressure on the composite assembly against the OML tool surface.

14. The method of claim 13 , wherein the step of applying heat to the composite assembly is performed using at least one of:

a convection oven, an autoclave, direct heating of the OML tool.

15. The method of claim 1 , further comprising the step of:

monitoring a temperature of at least one of the expandable material and the composite assembly when heating the layer of expandable material.

16. The method of claim 15 , wherein the step of monitoring the temperature of at least one of the expandable material and the composite assembly includes:

monitoring the temperature using an array of thermal sensors mounted to at least one of the OML tool, the IML tool, and the composite assembly.

17. The method of claim 16 , wherein the step of monitoring the temperature of at least one of the expandable material and the composite assembly includes:

tracking, using the thermal sensors, the temperature at different locations within the composite assembly.

18. The method of claim 1 , further comprising the step of:

adjusting a rate at which the internal compaction pressure is applied to the composite assembly by adjusting the heating of the expandable foam.

19. The method of claim 3 , wherein the step of applying a composite layup to the IML tool surface comprises at least one of:

filament winding composite material over the IML tool surface; and

fiber placing composite material on the IML tool surface.

20. The method of claim 19 , wherein:

the composite material comprises pre-preg.