Stampable Sheet with Segmented Carbon Fiber Orientation
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Solution Overview
Problem
Conventional stampable sheets with carbon fibers and resin exhibit poor moldability and low flowability due to fiber orientation and crossing, making it difficult to achieve isotropic mechanical properties and complex shape molding.
Innovation Solution
A stampable sheet comprising fiber bundles of discontinuous carbon fibers with a bundle width of 50 μm or greater and opened fibers, oriented in a specific angular distribution to balance fiber bundle and opened fiber proportions, enhancing stress dispersion and isotropy without complex lamination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If carbon fibers are dispersed to exhibit reinforcing effect, then mechanical properties are improved, but flowability at molding time deteriorates
Solution Approach 1:
The carbon fiber sheet is segmented into two distinct fiber components: fiber bundles (A) with bundle width of 50 μm or greater, and opened fibers (B) ranging from fiber bundles less than 50 μm to single fibers. This segmentation allows each component to fulfill different functions - bundles provide flowability while opened fibers provide reinforcement
Solution Approach 2:
Different regions of the fiber structure are assigned different properties: fiber bundles (A) are oriented primarily in the 0° direction to provide flowability, while opened fibers (B) are oriented in multiple directions including 90° to provide reinforcement and isotropy. Each local region contributes differently to the overall performance
2Stability of the object's composition
If carbon fibers are oriented along carding machine rotational direction, then fiber alignment is improved, but anisotropy increases
Solution Approach 1:
The patent deliberately creates asymmetric orientation distributions for the two fiber types: fiber bundles (A) show strong orientation in the 0° direction (aligned with machine direction), while opened fibers (B) show orientation in multiple directions including 90°. This asymmetric distribution of different fiber types compensates for the anisotropy introduced by carding
Solution Approach 2:
The patent adds a dimensional aspect to fiber orientation by considering angular zones from 0° to 90° and creating reverse gradient distribution patterns between the two fiber types across these angular zones, transforming a one-dimensional alignment problem into a two-dimensional orientation control problem
3Strength
If complex lamination is performed to achieve isotropy, then isotropic mechanical properties are improved, but manufacturing complexity increases
Solution Approach 1:
The patent merges the functions of multiple laminates into a single carbon fiber sheet by incorporating two differently oriented fiber populations (bundles and opened fibers) in one sheet structure, eliminating the need for complex multi-layer lamination while achieving isotropic properties
Solution Approach 2:
The desired isotropic fiber orientation distribution is built into the carbon fiber sheet during its manufacturing process (carding and treatment), so that when the sheet is molded, the isotropy is already present without requiring subsequent complex lamination operations
Data Source
AI summary
A stampable sheet includes a resin and carbon fiber sheet including fiber bundles of discontinuous carbon fibers, wherein the carbon fiber sheet includes fiber bundles having a bundle width of 50 μm or greater and opened fibers ranging from fiber bundles having a bundle width less than 50 μm to fibers obtained by opening to the single-fiber level. When the direction along which the opened fibers have been oriented most is a 0° direction and the range of from the 0° to 90° direction is divided into angular zones, the distribution curve showing the proportion of the number of fiber bundles in each angular zone to that in all angular zones and the distribution curve showing the proportion of the number of opened fibers in each angular zone to that in all angular zones are reverse to each other in terms of gradient of the 0° to 90° direction.