FIELD

The present disclosure generally relates to methods and equipment for fabricating composite resin parts, and generally relates to bladder systems that are used in curing composite parts.

BACKGROUND

Composite resin parts may be cured within an autoclave that applies heat and pressure to the composite part during a cure cycle. Some part geometries include internal cavities that may cause the composite part to collapse under autoclave pressure unless a tool such as an inflatable bladder is placed in a composite part cavity. Such an inflatable bladder may be inflated during a cure process so as to react to the autoclave pressure force applied to the composite part. Typically, these inflatable bladders are pressurized by venting them through a vacuum bag.

There are several problems with the vented bladders that often lead to inconsistencies in the cured parts. For example, failure to properly vent the bladder may prevent the bladder from becoming pressurized sufficiently to react to the applied autoclave pressures. Similarly, insufficient bladder pressurization may result from a failure of a sealant used to seal a vent hole coupling the bladder with an outside vent. It is also possible for a bladder wall to fail or be penetrated, in which event autoclave gases may be forced into the part throughout the cure cycle. In addition, it is sometimes difficult to design a nominal bladder cross section that is both small enough to fit inside a composite stringer prior to cure, yet large enough to expand to a desired cross section during cure. Moreover, because the bladders are flexible during lay up operations, it can be a manufacturing challenge for an Automated Fiber Placement machine operation particularly when orientation dictates that the ply must be laid in a perpendicular direction to that of the bladder: a situation that can cause excess fiber length to be laid.

Accordingly, there is a need for a bladder system that may reduce or eliminate the adverse effects resulting from leaks in the bladder or failure to properly pressurize the bladder. There is also a need for a bladder system that has a desired cross section that allows the bladder to expand during a cure process. There is also a need for a bladder system that reduces the cause of excess fiber length being laid.

SUMMARY

In one arrangement, a structure comprising a plurality of walls defining a bladder cavity is disclosed. The bladder cavity comprises an initial cross section size. A first plurality of wave features provided along at least one of the plurality of walls defining the bladder cavity. In one arrangement, the first plurality of wave features allow the structure to expand from the initial cross section size to a second cross section size after the structure becomes inflated during a composite charge cure, the second cross section size larger than the initial cross sectional size.

In one arrangement, the structure comprises a bottom wall, a first side wall extending from the bottom wall, a second side wall extending from the bottom wall, a first end wall, a second end wall, and a top wall extending from the first end wall to the second end wall enclosing the structure, such that the bottom wall, the first side wall, the second side wall, the first end wall, the second end wall, and the top wall define the bladder cavity, wherein at least one of the bottom wall, the top wall, the first side wall, the first end wall, the second end wall, or the second side wall comprises the first plurality of wave features. In one arrangement, the first plurality of wave features extend over a length of the at least one of the bottom wall, the top wall, the first side wall, the first end wall, the second end wall, or the second side wall.

In one arrangement, the first plurality of wave features extend over a portion of a length of the at least one of the bottom wall, the top wall, the first side wall, the first end wall, the second end wall, or the second side wall. In one arrangement, the first plurality of wave features comprise a plurality of uniform wave features. The first plurality of uniform wave features may comprise a similar radius of curvature. In one arrangement, at least one of the bottom wall, the top wall, the first side wall, the first end wall, the second end wall, or the second side wall comprises a second plurality of wave features. In such an arrangement, the first plurality of wave features may comprise a first radius of curvature and the second plurality of wave features comprise a second radius of curvature. The first radius of curvature may be different than the second radius of curvature.

In one arrangement, a pressure fitting is adapted to be coupled with a vacuum source for inflating the structure.

In one arrangement, a method of curing a charge is described. The method comprising the steps of placing a charge on a tool; installing a structure having an initial cross section size in a charge cavity of the charge placed on the tool; coupling the structure to a vent port; sealing a flex bag over the charge, the tool, and the structure; drawing a vacuum; debulking the charge by inflating the structure; beginning to expand the structure from the initial cross section size to a desired cross section size; increasing an effective pressure that is applied to an inside radii of the charge; finalizing debulking; and curing charge.

In one arrangement, a multilayered bladder system for use in curing of a composite charge having an internal cavity is disclosed. The multilayered bladder comprises a bladder outer layer. The bladder outer layer defining a top wall, a bottom wall, a first sidewall, and a second sidewall, wherein the first and second sides walls extend between the top wall and the bottom. The multilayered bladder further comprising a bladder first inner layer. The bladder first inner layer defining a top wall, a bottom wall, a first sidewall, and a second sidewall, wherein the first and second sides walls extend between the top wall and the bottom wall. The multilayered bladder further comprising a bladder intermediate layer disposed between the bladder outer layer and the bladder first inner layer. In one arrangement, the outer layer comprises an overlapping top wall. For example, in one arrangement, the overlapping top wall of the outer layer comprises a partially overlapping top wall.

In yet another alternative arrangement, the first inner layer comprises an overlapping top wall. For example, the overlapping top wall of the first inner layer comprises a partially overlapping top wall.

In one arrangement, the multilayered bladder comprises a layer of fiberglass provided within the overlapping top wall of the first inner layer. The multilayered bladder may further comprise a second inner layer, the second inner layer provided below the top wall of the first inner layer. For example, in one arrangement, the first inner layer comprises an overlapping top wall, and the second inner layer is provided below the overlapping top wall of the first inner layer. In one arrangement, the second inner layer comprises a fluoroelastic rubber layer.

In yet another arrangement, the multilayered bladder further comprises a plurality of fluoroelastic rubber layers provided between the top wall of the first inner layer and the intermediate layer.

In yet another arrangement, the multilayered bladder further comprises a second inner layer provided between the first inner layer and the intermediate layer. The second inner layer extends along at least a portion of the first sidewall of the first inner layer. In one arrangement, the second inner layer comprises fluoroelastic rubber.

In yet another arrangement, the top wall of the outer layer comprises a first thickness and the first sidewall and the second side wall of the outer layer comprises a second thickness. In one arrangement, the first thickness of the top wall of the outer layer is different than the second thickness of the first and second sidewalls of the outer layer.

In one arrangement, a method of curing a charge is disclosed. The method comprising the steps of placing a charge on a tool; positioning a multilayered structure in a charge cavity defined by the charge placed on the tool; coupling the multilayered structure to a vent port; covering the charge, the tool, and the multilayered structure with a flex bag over; drawing a vacuum; initiating a debulking process of the charge by inflating the multilayered structure; finalizing debulk; and curing the charge.

In one arrangement, a bladder system for use in curing a composite charge having an internal cavity is disclosed. The bladder system comprising a bladder comprising a bladder bottom wall, a first bladder side wall extending from the bottom wall, a second bladder side wall extending from the bottom wall, and a bladder top wall extending from a bladder front wall to a bladder back wall enclosing the bladder. The bladder bottom wall, the first bladder side wall, the second bladder side wall, the bladder top wall, the bladder front wall, and the bladder back wall define a bladder cavity. A flexible bladder support is positioned within the bladder cavity, such that a first bearing surface of the flexible bladder support and a second bearing surface of the flexible bladder support provide a compressive load support between a bottom surface of the bladder top wall and a top surface of the bladder bottom wall. In one arrangement, the bladder support further provides the compressive load support between an inner surface of the bladder first side wall and an inner surface of the bladder second side wall. In one arrangement, the flexible bladder support comprises at least one corkscrew support.

In another arrangement, the flexible bladder support comprises a sinusoidal support. In one arrangement, the sinusoidal support comprises a constant width along a length of the sinusoidal support. In one arrangement, an additional support is provided between the bladder top wall and the sinusoidal support. In one arrangement, the additional support provided between the bladder top wall and the sinusoidal support comprises a rectangular support.

In one arrangement, the support structure comprises a segmented support.

In one arrangement, the flexible bladder support comprises a double concave support. For example, in one arrangement, the double concave support comprises a top bearing surface, a bottom bearing surface, a first side support, and a second side support. The first side support extends in a concave manner from a first end of the bottom bearing surface to a first end of the top bearing surface. The second side support extends in a concave manner between a second end of the bottom bearing surface upwards towards a second end of the top bearing surface.

In one bladder system arrangement, the flexible bladder support extends along an entire length of the bladder. In yet another bladder system arrangement, the bladder system comprises a bladder system comprising wave features. In yet another bladder system arrangement, the bladder system comprises a multilayered bladder system.

In yet another arrangement, a bladder system for use in curing a composite charge having an internal cavity is disclosed. The bladder system comprising a bladder comprising a bladder bottom wall, a first bladder side wall extending from the bottom wall, a second bladder side wall extending from the bottom wall, and a bladder top wall extends from a bladder front wall to a bladder back wall enclosing the bladder. The bladder bottom wall, the first bladder side wall, the second bladder side wall, and the bladder top wall define a bladder cavity. A flexible bladder support is positioned within the bladder cavity, such that a first bearing surface of the flexible bladder support and a second bearing surface of the flexible bladder support provide a compressive load support between a bottom surface of the bladder top wall and an inner surface of the bladder first side wall and an inner surface of the bladder second side wall. In one arrangement, the flexible bladder support comprises a trapezoidal bladder support. In one arrangement, the bladder support comprises a segmented flexible bladder support.

In an alternative arrangement, the bladder support comprises a double concave support structure. In one arrangement, the double concave support structure comprises a top bearing surface, a bottom bearing surface, a first side support, and a second side support. The first side support extends in a concave manner from a first end of the bottom bearing surface to a first end of the top bearing surface. The second side support extends in a concave manner between a second end of the bottom bearing surface upwards towards a second end of the top bearing surface. In one arrangement, the bladder support comprises a segmented bladder support.

In an alternative arrangement, a method of curing a charge is disclosed. The method comprising the steps of placing a charge on a tool; positioning a bladder in a charge cavity defined by the charge placed on the tool; positioning a bladder support into a bladder cavity defined by the bladder; laying up a plurality of plies over the structure and the bladder support; providing a compressive load support by the bladder support; coupling the bladder to a vent port; covering the charge, the tool, and the bladder with a flex bag over; drawing a vacuum; initiating a debulking process of the charge by inflating the bladder; finalizing debulk; and curing the charge.

The features, functions, and advantages can be achieved independently in various arrangements of the present disclosure or may be combined in yet other arrangements in which further details can be seen with reference to the following description and drawings.

