Carbon fiber reinforced plastic (CFRP) stringer termination softening with stacked CFRP noodle

A method of controlling delamination and separation between a composite stringer and a composite structure, the method comprising:

• providing a base flange of the composite stringer, the base flange comprising a bottom surface configured for coupling to the composite structure and an acreage region, a transition region, and a runout region along a longitudinal length;
• providing a web extending away from the base flange, the web comprising a bottom adjacent to the base flange and a top edge opposite the bottom, the web extending along the acreage region, the transition region, and the runout region of the longitudinal length;
• providing a noodle having a noodle length substantially corresponding to the longitudinal length and configured to substantially fill a stringer cavity defined between the base flange and the web along the longitudinal length, wherein providing the noodle comprises
• providing a unidirectional fiber top portion;
• providing a stacked laminate bottom portion comprising a plurality of stacks, wherein providing each of the plurality of stacks comprises
• abutting a first ply having a first ply orientation against a second ply having a second ply orientation,
• abutting the second ply against a third ply having a third ply orientation along the acreage region of the noodle length, and
• terminating the second ply within the transition region of the noodle length;
• and
• bonding the bottom surface of the base flange to a top surface of the composite structure.

A stringer having a longitudinal length defining an acreage region, a transition region, and a runout region, the stringer comprising:

• a base flange comprising a plurality of plies and a bottom surface configured for coupling to a vehicle skin, wherein a number of plies of the plurality of plies decreases in the transition region;
• a web extending away from the base flange, the web comprising a bottom adjacent to the base flange and a top edge opposite the bottom, wherein the top edge of the web is trimmed from a first height at the top edge at a first height location in the transition region to a second height proximate to the bottom at a web termination location in the runout region;
• and
• a noodle having a noodle length substantially corresponding to the longitudinal length and configured to substantially fill a stringer cavity defined between the base flange and the web along the longitudinal length, the noodle comprising
• a unidirectional fiber top portion having a constant cross-sectional area throughout the acreage region and the transition region;
• and
• a stacked laminate bottom portion coupled to the unidirectional fiber top portion, the stacked laminate bottom portion comprising a plurality of stacks, each of the plurality of stacks comprising
• a first ply having a first ply orientation, a second ply abutting the first ply and having a second ply orientation, and a third ply abutting the second ply and having a third ply orientation along the acreage region of the noodle length, and
• the first ply having the first ply orientation and the third ply having the third ply orientation abutting the first ply along the transition region of the noodle length.