Composite Feedstock Strips via Slitting and Coating
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Solution Overview
Problem
Current additive manufacturing techniques face challenges in incorporating continuous fibers, leading to difficulties in achieving superior mechanical properties and complex geometries due to issues like clogging and voids in composite feedstock, especially for aerospace applications.
Innovation Solution
The method involves forming composite feedstock strips with continuous unidirectional fibers by slitting a laminated sheet parallel to the fibers and coating the strips with a second resin, preserving fiber continuity and orientation, which allows for uniform fiber distribution and enhanced mechanical properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If extrusion techniques are used to fabricate composite feedstock, then continuous fibers can be incorporated, but clogging and voids occur in the feedstock
Solution Approach 1:
The process segments the feedstock fabrication into two distinct stages: first forming a composite laminate sheet with continuous fibers, then slitting it into strips. This segmentation allows the fiber-containing laminate to be formed without clogging (since fibers are not forced through a nozzle), and then divided into usable strips for additive manufacturing, eliminating the voids and defects caused by extrusion.
Solution Approach 2:
The invention performs preliminary action by forming the complete composite laminate sheet with continuous fibers before slitting it into strips. The laminate is fabricated with fibers already embedded in the matrix material, ensuring fiber continuity and proper distribution before the final stripping operation, which prevents fiber disruption and maintains feedstock quality.
2Strength
If continuous fibers are incorporated into additive manufacturing feedstock, then superior mechanical properties are achieved, but fiber disruption and clogging occur
Solution Approach 1:
The invention inverts the conventional approach by not forcing fibers through a nozzle during extrusion. Instead, it first creates a laminate sheet containing continuous fibers, then slits this sheet into strips. This inversion eliminates clogging (since fibers never encounter a restrictive nozzle) while preserving fiber continuity and mechanical properties.
3Strength
If slitting is performed parallel to fibers, then fiber continuity is preserved, but manufacturing complexity increases
Solution Approach 1:
The slitting process applies local quality by making precise cuts only at specific locations perpendicular to the fiber direction, preserving fiber continuity in the main direction while creating the necessary strip geometry. The coating process then applies a different material property (release agent) specifically at the strip surfaces, creating localized functional zones without disrupting overall fiber continuity.
4Shape
If coating is applied to slit strips, then cross-sectional shape can be modified, but processing time increases
Solution Approach 1:
The coating operation performs a preliminary action by applying a release agent or additional matrix material to the slit strips before they are used in additive manufacturing. This preliminary coating modifies the cross-sectional shape and provides necessary surface properties, and can be integrated into the manufacturing flow to minimize additional processing time.
Data Source
Figure 1A
Figure 1B
Figure 2A~2B
AI summary
Provided are composite feedstock strips for additive manufacturing and methods of forming such strips. A composite feedstock strip may include continuous unidirectional fibers extending parallel to each other and to the principal axis of the strip. This fiber continuity yields superior mechanical properties, such as the tensile strength along strip's principal axis. Composite feedstock strips may be fabricated by slitting a composite laminate in a direction parallel to the fibers. In some embodiments, the cross-sectional shape of the slit strips may be changed by reattributing material at least on the surface of the strips and/or by coating the slit strips with another material. This cross-sectional shape change may be performed without disturbing the continuous fibers within the strips. The cross-sectional distribution of fibers within the strips may be uneven with higher concentration of fibers near the principal axis of the strips, for example, to assist with additive manufacturing.