In-tool compaction for composite structures

A method for in-tool compaction of an out-of-plane feature of a composite structure, the method comprising:

• forming a stiffener preform;
• placing an insert adjacent an out-of-plane feature of the stiffener preform;
• placing a second insert adjacent the out-of-plane feature of the stiffener preform;
• placing the stiffener preform, the insert, and the second insert into a preform holding fixture to form a stiffener preform assembly, the preform holding fixture in contact with and constraining the insert, the second insert, and the stiffener preform;
• inserting the stiffener preform assembly into a cavity of a tool, wherein the insert comprises a first face complementary to an angled surface of the cavity and the insert comprises a second face complementary to a compaction surface of the out-of-plane feature of the stiffener preform, the first face opposite the second face, and wherein the second insert comprises a third face complementary to a second angled surface of the cavity and the second insert comprises a fourth face complementary to a second compaction surface of the out-of-plane feature of the stiffener preform, the second insert continuously spaced from the insert on opposite sides of the out-of-plane feature;
• and
• applying a force on the stiffener preform or the insert such that the second face of the insert transmits a compression force on the compaction surface of the stiffener preform;
• wherein the preform holding fixture has a cross section complementary to the angled surface of the cavity and the first face of the insert and wherein the stiffener preform assembly is configured to be transported to and inserted into the cavity as a whole.

A stiffener preform assembly for in-tool compaction of out-of-plane features of a stiffener preform, the assembly comprising:

• a cavity formed in a tool, the cavity comprising an angled surface;
• a stiffener preform comprising an out-of-plane feature, the out-of-plane feature comprising a compaction surface;
• an insert comprising a first face complementary to an angled surface of the cavity of the tool and a second face complementary to the compaction surface, the first face opposite the second face;
• and
• a second insert, the second insert comprising a third face complementary to a second angled surface of the cavity and a fourth face complementary to a second compaction surface of the out-of-plane feature, the second insert continuously spaced from the insert on opposite sides of the out-of-plane feature;
• and
• a preform holding fixture having a cross section complementary to the angled surface of the cavity of the tool and the first face of the insert, the preform holding fixture in contact with the insert, the second insert, and the stiffener preform, the preform holding fixture including a non-adhesive inner layer for contact with the out-of-plane feature, the insert, and the second insert;
• wherein the stiffener preform assembly is configured to be transported to and inserted into the cavity of the tool as a whole.