A panel includes a corrugated base with base corrugations configured from first base segments and second base segments. A first of the base corrugations includes a first of the first base segments and a first of the second base segments that is non-parallel to the first of the first base segments. The first of the base corrugations forms a first channel that extends laterally between and longitudinally along the first of the first base segments and the first of the second base segments. A corrugated stringer includes a plurality of stringer corrugations arranged longitudinally along and within the first channel. The stringer corrugations are configured from first stringer segments and second stringer segments. A first of the stringer corrugations includes a first of the first stringer segments and a first of the second stringer segments that is non-parallel to the first of the first stringer segments.

A reinforcing member includes a flange portion extending along a surface of a target member to be reinforced, a web portion extending in a direction intersecting the surface, a joint connecting the flange portion and the web portion. In a filler space formed between the joint and the surface, a filler is placed. The filler is at least partially surrounded by a foam resin in the filler space.

A composite structure forming system configured to form a contoured elongate composite structure in a continuous process is presented. The composite structure forming system comprises a plurality of charge forming stations and a plurality of conveyor systems. The plurality of charge forming stations is configured to operate in parallel, each charge forming station of the plurality of charge forming stations is configured to form a respective composite charge of the contoured elongate composite structure. Each conveyor system of the plurality of conveyor systems is configured to transport a respective composite charge through a respective charge forming station.

Stringers and aircraft skin structures and related methods are disclosed. An example apparatus includes a skin structure and a support. The support includes a first surface, a second surface opposite the first surface, and a tapered edge extending from the first surface. The example apparatus includes a first material disposed between a first portion of the support and a first portion of the skin structure to couple the second surface of the support to the skin structure and a second material disposed between a second portion of the support and a second portion of the skin structure. The second material is different than the first material. The second portion of the support includes at least a portion of the tapered edge.

In an example, a composite structure having a variable gage is described. The composite structure includes a first end having a first gage, a second end having a second gage, which is less than the first gage, a plurality of continuous plies, and a plurality of drop-off plies. Each continuous ply extends from the first end to the second end. Each drop-off ply includes a tip having a tapered shape. Each drop-off ply extends from the first end to a respective position of the tip of the drop-off ply between the first end and the second end. The plurality of drop-off plies are separated from each other by at least one of the plurality of continuous plies.

In an example, a composite structure having a variable gage is described. The composite structure includes a first end having a first gage, a second end having a second gage, which is less than the first gage, a plurality of continuous plies, and a plurality of drop-off plies. Each continuous ply extends from the first end to the second end. Each drop-off ply includes a tip having a blunt-end shape. Each drop-off ply extends from the first end to a respective position of the tip of the drop-off ply between the first end and the second end. The plurality of drop-off plies are separated from each other by at least one of the plurality of continuous plies.

In an example, a composite structure having a variable gage is described. The composite structure includes a first end having a first gage, a second end having a second gage, which is less than the first gage, a plurality of continuous plies, and a plurality of drop-off plies. Each continuous ply extends from the first end to the second end. Each drop-off ply includes a tip having a tapered shape. Each drop-off ply extends from the first end to a respective position of the tip of the drop-off ply between the first end and the second end. The tips of the plurality of drop-off plies are arranged in a monotonically-inward pattern.

A method for fabricating a composite wing structural component for an aircraft is described. The method comprises extruding a filler material into each mold channel of a plurality of mold channels of a die to form a plurality of filler segments, removing the plurality of filler segments from the plurality of mold channels of the die, and arranging the plurality of filler segments in a space in the composite structural component, the space being defined by a radius of the composite structural component, such that the filler segments are in end-to-end contact. The method further comprises curing the plurality of filler segments in the space to fuse the plurality of filler segments.

A method of manufacturing a cured composite structure includes placing a radius filler element into a radius cavity extending along a length of a composite base member. The radius filler element is formed of a permeable material. The method also includes absorbing resin from the composite base member into the permeable material of the radius filler element. The method additionally includes curing or solidifying the resin in the radius filler element and in the composite base member to form a cured composite structure in which the resin bonds the radius filler element to the composite base member.

Some embodiments are directed to an apparatus, such as a panel that might be appropriate for aircraft or space vehicle fuel tanks. According to some embodiments, a plurality of stiffening elements may be attached to a matrix stiffened laminate skin and arranged in an isogrid pattern. Each stiffening element may include, for example, a hollow hat-shaped and substantially rectangular cross-sectional profile and a layer of unidirectional fibers proximate to a top portion of the stiffening element. In some embodiments, the stiffening elements may be created on top of a core element that is later removed (e.g., by dissolving, melting, or vaporizing the core element after the stiffening elements and fiber skin are cured with heat).