Isogrid Stiffening Elements via Core Removal
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Solution Overview
Problem
Existing methods for creating isogrid stiffening elements are difficult and expensive to manufacture, making it challenging to efficiently and accurately produce structural panels that require substantial stiffness while minimizing material usage, such as those needed for aircraft or space vehicle fuel tanks.
Innovation Solution
A method involving a core element placed in an isogrid pattern on a matrix stiffened laminate skin, with hollow hat-shaped stiffening elements created over the core that include unidirectional fibers, which are then cured and have the core removed, either by dissolving, melting, or vaporizing, to produce lightweight and strong panels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If traditional honeycomb or stringer stiffening elements are used, then structural stiffness is achieved, but the panel weight increases significantly
Solution Approach 1:
The panel is segmented into a grid pattern with stiffening elements positioned at intersections, dividing the structure into manageable triangular panels. This segmentation provides structural stiffness at critical locations without requiring continuous heavy reinforcement across the entire panel surface.
Solution Approach 2:
The stiffening elements are constructed using composite materials including a core element, a hat-shaped stiffening element, and unidirectional fibers. This composite structure achieves high strength-to-weight ratio, providing structural stiffness while minimizing panel weight compared to traditional homogeneous materials.
2Quantity of substance
If isogrid configuration of triangular integral stiffening ribs is used, then material usage is minimized, but manufacturing difficulty and cost increase
Solution Approach 1:
A core element is placed in the desired isogrid pattern before the stiffening elements are formed around it. This preliminary placement of the core element guides the formation of the hat-shaped stiffening elements and ensures accurate positioning, simplifying the manufacturing process compared to attempting to form the complex isogrid pattern without a template.
Solution Approach 2:
The core element serves as an intermediary tool that facilitates the creation of the isogrid pattern. It is temporarily present during manufacturing to enable precise positioning and formation of the stiffening elements, then removed after curing, leaving the desired isogrid structure without the complexity of direct isogrid fabrication.
3Shape
If core element removal by dissolving, melting, or vaporizing is used, then the desired hollow hat-shaped stiffening elements are achieved, but additional processing steps are required
Solution Approach 1:
The core element is removed by inducing phase transitions - dissolving (solid to solution), melting (solid to liquid), or vaporizing (solid to gas). These phase transitions enable clean removal of the core element after curing, creating the desired hollow interior of the hat-shaped stiffening elements without complex mechanical removal processes.
Solution Approach 2:
The core element is designed as a temporary, disposable component that serves its purpose during manufacturing (providing form and positioning) and is then easily removed. This approach simplifies the overall manufacturing process by using a simple removable core rather than attempting to create the hollow shape through complex direct forming methods.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach enables the efficient and accurate creation of isogrid stiffening elements, resulting in panels that are approximately 25% lighter than honeycomb panels and half the weight of conventional stringer stiffened aluminum panels, while avoiding environmental issues associated with traditional honeycomb cores.
Implementation Method 1
a core element placed in an isogrid pattern on a matrix stiffened laminate skin, with hollow hat-shaped stiffening elements created over the core that include unidirectional fibers, which are then cured and have the core removed, either by dissolving, melting, or vaporizing
Implementation Method 2
a core element placed in an isogrid pattern on a matrix stiffened laminate skin, with hollow hat-shaped stiffening elements created over the core that include unidirectional fibers, which are then cured and have the core removed, either by dissolving, melting, or vaporizing
Implementation Method 3
a core element placed in an isogrid pattern on a matrix stiffened laminate skin, with hollow hat-shaped stiffening elements created over the core that include unidirectional fibers, which are then cured and have the core removed, either by dissolving, melting, or vaporizing
Implementation Method 4
a core element placed in an isogrid pattern on a matrix stiffened laminate skin, with hollow hat-shaped stiffening elements created over the core that include unidirectional fibers, which are then cured and have the core removed
Data Source
AI summary
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).