Patent Application
20110039057
The present disclosure relates to structural rods which reinforce structural panel stringers. More particularly, the present disclosure relates to a pre-cured laminated composite rod and a fabrication method for a laminated composite rod which is suitable for supporting structural panel stringers during resin infusion and curing of the stringers and which can be tailored to meet design requirements and reduce thermal stresses in a panel stringer by providing a reduced Coefficient of Thermal Expansion.
The PRSEUS (Pultruded Rod Stitched Efficient Structure) structural design concept may require a rod to support the panel stringers during assembly, infusion and cure of the stringers. The rod used in the current panel stringer design may be made by a process-pultrusion- that results in the rod having all zero degree orientation fibers. This process may result in a rod with a higher stiffness and Coefficient of Thermal Expansion than is required in most design situations. The zero degree fibers running longitudinally may undergo diametric expansion and provide no constraint on resin expansion across the diameter of the rod during cure. This architecture of the rod may yield high residual cure stresses and result in cracking of the resin in the layer between the rod and the wrap ply.
Methods which have been proposed to improve the pultruded rod have included helical wrapping of the rod with fibers that are intended to partially constrain the resin expansion. These solutions, however, may remove only a small portion of the zero degree fibers and greatly increase the part cost for the pultruded rods. Moreover, the existing pultruded rod design may be attended by residual stresses in the rod-to-wrap interface of the panel stringer.
The conventional pultruded rod may be formed with all zero degree fibers and therefore, may be very stiff with little amenability to tailor the properties to meet different requirements. Additionally, the pultruded rod may exhibit a very high Coefficient of Thermal Expansion due to the 100% zero degree dominated architecture.
Therefore, a pre-cured laminated composite rod is needed which is suitable for supporting structural panel stringers during resin infusion and curing of the stringers and which can be tailored to meet design requirements and reduce thermal stresses in a panel stringer by providing a reduced Coefficient of Thermal Expansion.
The present disclosure is generally directed to a laminated composite rod. An illustrative embodiment of the laminated composite rod includes a rod body having a generally circular or oval cross-section and comprising a plurality of laminated composite plies disposed at various orientations with respect to each other.
The present disclosure is further generally directed to a rod stitched efficient composite structure comprising a stitched composite structure and a pre-cured laminated composite rod having a generally circular or oval cross-section and incorporated in the stitched composite structure.
The present disclosure is further generally directed to a laminated composite rod fabrication method. An illustrative embodiment of the method includes providing a plurality of composite plies, forming a laminated composite panel by laying down the composite plies, curing the laminated composite panel and forming a laminated composite rod having a generally circular or oval cross-section from the laminated composite panel.
In some embodiments, the rod stitched efficient composite structure comprises a skin panel assembly; a pre-cured laminated composite rod comprising a rod body including a plurality of laminated composite plies selected from the group consisting of graphite tape, epoxy tape and a prepreg material devoid of pultruded plies and disposed at different orientations with respect to each other in the rod body; and a rod stitched efficient structure panel assembly comprising a pair of adjacent stringer panels, a panel wrap connecting the stringer panels and extending around the laminated composite rod and a pair of panel flanges extending from the stringer panels and stitched to the skin panel assembly.
In some embodiments, the rod stitched efficient composite structure may include a skin panel assembly; a pre-cured laminated composite rod comprising a rod body including a plurality of laminated composite plies selected from the group consisting of graphite tape, epoxy tape and a prepreg material devoid of pultruded plies and disposed at different orientations with respect to each other in the rod body; and a rod stitched efficient structure panel assembly comprising a pair of adjacent stringer panels, a panel wrap connecting the stringer panels and extending around the laminated composite rod and a pair of panel flanges extending from the stringer panels and stitched to the skin panel assembly.
In some embodiments, the laminated composite rod fabrication method may include providing a plurality of composite plies selected from the group consisting of graphite tape, epoxy tape and a prepreg material and devoid of pultruded plies; forming a laminated composite panel by laying down the composite plies at various orientations with respect to each other; curing the laminated composite panel; forming a laminated composite rod from the laminated composite panel by cutting and machining the laminated composite panel; subjecting the laminated composite rod to surface abrasion; providing a rod stitched efficient structure panel assembly comprising a pair of adjacent stringer panels, a panel wrap connecting the stringer panels and a pair of panel flanges extending from the stringer panels; inserting the laminated composite rod in the panel wrap of the stringer; providing a skin panel assembly; stitching the pair of panel flanges of the stringer to the skin panel assembly; infusing resin into the stringer; and curing the stringer.
The following detailed description is merely exemplary in nature and is not intended to limit the described embodiments or the application and uses of the described embodiments. As used herein, the word “exemplary” or “illustrative” means “serving as an example, instance, or illustration.” Any implementation described herein as “exemplary” or “illustrative” is not necessarily to be construed as preferred or advantageous over other implementations. All of the implementations described below are exemplary implementations provided to enable persons skilled in the art to practice the disclosure and are not intended to limit the scope of the claims. Furthermore, there is no intention to be bound by any expressed or implied theory presented in the preceding technical field, background, brief summary or the following detailed description.
Referring initially to
As shown in
After it is cured, the laminated composite panel 6 may be subjected to rough cutting to generally transform the shape of the laminated composite panel 6 into the shape of the laminated composite rod 16. Rough cutting of the laminated composite panel 6 may be accomplished using water jet techniques or suitable alternative techniques which are known to those skilled in the art. The laminated composite panel 6 may then be machined into the final desired shape of the laminated composite rod 16. In some embodiments, the machined laminated composite rod 16 may be subjected to surface abrasion and/or other surface preparation treatments. As shown in
As shown in
The panel flanges 24 of the panel assembly stringer 20 may be attached to a skin panel assembly 30. In some embodiments, the panel assembly stringer 20 may be attached to a base panel 26 which may be attached to the skin panel assembly 30. Stitching 25 may be used to attach the adjacent stringer panels 21 to each other and the panel flanges 24 to the skin panel assembly 30. After attachment of the panel assembly stringer 20 to the skin panel assembly 30, the panel assembly stringer 20 may be placed in a vacuum bag (not shown). Resin (not shown) may be infused into the fabric of the panel assembly stringer 20, after which the panel assembly stringer 20 may be cured.
The laminated composite rod 16 may be tailored to match varying structural requirements and greatly reduces the Coefficient of Thermal Expansion (CTE) between the pre-cured laminated composite rod 16 and the surrounding infused fabric portions of the panel assembly stringer 20. Moreover, due to the low CTE of the laminated composite rod 16, residual stresses may be substantially reduced during curing of the panel assembly stringer 20, reducing or eliminating interfacial cracking at the rod-to-wrap interface 23 of the panel assembly stringer 20. The laminated composite rod 16 may be designed with tailorable strength and stiffness characteristics for specific structural applications by varying the number, sequence and orientation of the laminated composite panel 6 (
Referring next to
In block 804, the laminated composite panel may be sealed in an autoclave using vacuum bagging. In block 806, the laminated composite panel may be cured. In block 808, the laminated composite panel may be subjected to a rough cutting process in which the laminated composite panel is cut into the general configuration of a laminated composite rod. The rough cutting process may be implemented using a water jet or other cutting process. In block 810, the laminated composite panel may be machined to form the laminated composite rod. In block 812, the laminated composite rod may be subjected to surface abrasion and/or other surface preparation techniques.
In block 814, the laminated composite rod may be inserted into a panel assembly stringer. In block 816, the fabric panel flanges of the panel assembly stringer may be stitched or otherwise attached to a skin panel assembly. In block 818, the panel assembly stringer may be sealed in vacuum bagging. In block 820, resin may be infused into the panel fabric of the panel assembly stringer. In block 822, the panel assembly stringer may be cured.
Referring next to
Each of the processes of method 78 may be performed or carried out by a system integrator, a third party, and/or an operator (e.g., a customer). For the purposes of this description, a system integrator may include without limitation any number of aircraft manufacturers and major-system subcontractors; a third party may include without limitation any number of vendors, subcontractors, and suppliers; and an operator may be an airline, leasing company, military entity, service organization, and so on.
As shown in
The apparatus embodied herein may be employed during any one or more of the stages of the production and service method 78. For example, components or subassemblies corresponding to production process 84 may be fabricated or manufactured in a manner similar to components or subassemblies produced while the aircraft 94 is in service. Also one or more apparatus embodiments may be utilized during the production stages 84 and 86, for example, by substantially expediting assembly of or reducing the cost of an aircraft 94. Similarly, one or more apparatus embodiments may be utilized while the aircraft 94 is in service, for example and without limitation, to maintenance and service 92.
Although the embodiments of this disclosure have been described with respect to certain exemplary embodiments, it is to be understood that the specific embodiments are for purposes of illustration and not limitation, as other variations will occur to those of skill in the art.
