Rib-Stiffened Composite Grid Structure Node Thickness
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Solution Overview
Problem
The economical manufacturing of grid-stiffened structures using advanced composite materials is challenging due to increased thickness at nodes, reduced structural efficiency, and susceptibility to moisture absorption leading to delamination.
Innovation Solution
Incorporating a lightweight core material within the rib structure itself, using advanced composite surfaces with continuous fiber reinforcement and innovative manufacturing methods like overmolding and additive manufacturing to create grid-stiffened structures with reduced node thickness and improved stiffness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If continuous fiber composites are used to create grid-stiffened structures, then structural strength and stiffness are improved, but the thickness at nodes increases which reduces structural efficiency
Solution Approach 1:
The patent divides the rib structure into three distinct segments: a face sheet, a rib cap, and a core material. This segmentation allows each component to be optimized independently - the face sheet and rib cap provide structural strength with continuous fibers, while the core material fills the space between them without causing excessive node thickness, thereby resolving the contradiction between strength and node thickness.
Solution Approach 2:
The patent implements a nested structure where the core material is positioned between and supported by the face sheet and rib cap, creating a sandwich-like configuration. This nesting allows the core to contribute to stiffness and strength while maintaining compact node dimensions, as the core is enclosed within the structural framework rather than adding external thickness.
2Strength
If a lightweight core is sandwiched between composite skins to improve structural efficiency, then specific strength and stiffness are maximized, but the encapsulated core absorbs moisture leading to delamination and failure
Solution Approach 1:
The patent extracts the core material from full encapsulation between composite skins and instead positions it within a开放式 framework where the rib cap provides partial coverage. This extraction eliminates the moisture trapping issue while maintaining structural efficiency, as the core is exposed to airflow and can dry naturally without being sealed in a moisture-prone sandwich structure.
Solution Approach 2:
Instead of enclosing the core between two composite skins (traditional sandwich structure), the patent inverts the approach by using the rib cap to provide only partial coverage over the core, leaving it partially exposed. This inversion transforms the core from a moisture-vulnerable encapsulated element to a moisture-resilient structure that can breathe and dry, thereby improving reliability.
3Weight of moving object
If complex molding or machining is used to create rib-like features in isotropic materials, then weight reduction is achieved, but manufacturing cost increases
Solution Approach 1:
The patent replaces traditional isotropic materials with a composite structure consisting of fiber-reinforced face sheets and rib caps combined with a lightweight core material. This composite approach achieves superior strength-to-weight ratio without requiring complex molding or machining operations, as the components can be manufactured separately and assembled, thereby reducing manufacturing cost while maintaining weight reduction benefits.
Solution Approach 2:
The patent segments the structure into modular components (face sheet, rib cap, and core) that can be manufactured independently using simpler processes and then assembled. This segmentation eliminates the need for complex single-piece molding or machining operations, reducing manufacturing cost while achieving the desired weight reduction through optimized material distribution.
Data Source
AI summary
A rib-stiffened composite structure includes a composite face sheet having a continuous reinforcing fiber in a polymer matrix. A polymer core is in a grid pattern disposed on the composite face sheet, the grid pattern having a first series of paths crossing over a second series of paths. Material voids are formed in the spaces between the series of paths. A composite rib-cap is disposed upon an upper surface of the polymer core. The composite rib-cap includes a continuous reinforcing fiber in a polymer matrix. The fibers of the continuous reinforcing fiber of the polymer matrix of the composite rib cap are oriented in a direction along the first and second series of paths of the grid pattern of the extruded polymer core.