Patent Application
20240165912
The information provided in this section is for the purpose of generally presenting the context of the disclosure. Work of the presently named inventors, to the extent it is described in this section, as well as aspects of the description that may not otherwise qualify as prior art at the time of filing, are neither expressly nor impliedly admitted as prior art against the present disclosure.
The present disclosure relates to composites including bast fibers, and more particularly to composites with bast fiber having minimum bending lengths.
Natural fibers include bast, leaf, seed, wood, and grass stem. Bast fibers include flax, hemp, jute, ramie and kenaf. To increase sustainability and renewability, bast fibers may be used instead of other types of reinforcing fibers such as carbon fibers or glass fibers when manufacturing structural and semi-structural composite components.
A composite panel includes a polymer matrix and a plurality of reinforcing fibers encapsulated in the polymer matrix. The plurality of reinforcing fibers includes bast fibers having a predetermined bending length greater than 80 μm and less than 2 mm.
In other features, the plurality of reinforcing fibers are discontinuous fibers and are not aligned in the composite panel. The plurality of reinforcing fibers are discontinuous fibers and are aligned in a predetermined direction in the composite panel. The reinforcing fibers comprise at least one of continuous fiber tows and twine that are spun together.
In other features, the at least one of the continuous fiber tows and twine are aligned in the composite panel. The at least one of the continuous fiber tows and twine are attached to a surface of a backing sheet using stitches. The polymer matrix, the backing sheet, and the at least one of the continuous fiber tows and twine are encapsulated in the polymer matrix. The reinforcing fibers comprise cloth that is woven from at least one of continuous fiber tows and twine including the reinforcing fibers that are spun together.
In other features, the bast fibers comprise flax. The polymer matrix is opaque. The predetermined bending length is greater than 80 μm and less than 1 mm.
A composite panel comprise a polymer matrix and at least one of continuous fiber tows and twine, wherein the at least one of the continuous fiber tows and twine are encapsulated in the polymer matrix. The at least one of continuous fiber tows and twine includes bast fibers having a predetermined bending length greater than 80 μm and less than 2 mm that are spun together.
In other features, the at least one of the continuous fiber tows and twine are aligned in a first direction in the composite panel. The at least one of the continuous fiber tows and twine are attached to a surface of a backing sheet using stitches. The polymer matrix, the backing sheet, and the at least one of the continuous fiber tows and twine are encapsulated in the polymer matrix.
In other features, the bast fibers comprise flax. The polymer matrix is opaque. The predetermined bending length is greater than 80 μm and less than 1 mm.
A composite panel includes a polymer matrix and woven cloth encapsulated in the polymer matrix. The woven cloth comprises at least one of continuous fiber tows and twine that are woven together. The at least one of the continuous fiber tows and twine comprise a plurality of bast fibers having bending lengths greater than 80 μm and less than 2 mm that are spun together.
In other features, the woven cloth is attached to a surface of the backing sheet using stitches. The polymer matrix, the backing sheet, and the woven cloth are encapsulated in the polymer matrix.
In other features, the bast fibers comprise flax. The polymer matrix is opaque. The predetermined bending length is greater than 80 μm and less than 1 mm.
Further areas of applicability of the present disclosure will become apparent from the detailed description, the claims, and the drawings. The detailed description and specific examples are intended for purposes of illustration only and are not intended to limit the scope of the disclosure.
The present disclosure will become more fully understood from the detailed description and the accompanying drawings, wherein:
In the drawings, reference numbers may be reused to identify similar and/or identical elements.
While composites with bast fibers having minimum bending lengths are described below in the context of vehicle applications, the composites with bast fibers can be used in other applications.
Natural fibers include bast, leaf, seed, wood, and grass stem. Bast fibers include flax, hemp, jute, ramie and kenaf. Bast fibers such as flax can be used as reinforcing fibers in a polymer matrix. For example, the reinforcing fibers can be mixed with polymer and used in injection molding, molding of structural and semi-structural composites, and additive manufacturing such as 3D printing of components.
Flax fibers have excellent properties for use as reinforcing fibers such as a density of approximately 1.38 g/cm3, a tensile strength of 700 to 1000 MPa, a Young's modulus of 60-70 GPa, and an elongation of 2.3% at break.
During processing of bast fibers, the fibers are fed in a random, misaligned manner and bending lengths of the fibers vary after passing through the roller system during scutching/breaking. Bending length refers to the distance between adjacent bends of a bast fiber after passing through the roller system. In other words, as the fibers pass through the roller systems, the fibers are bent at fiber bending lengths that are relatively short (e.g., typically less than 30 μm). The fibers break at variable fiber lengths.
The roller systems described below control the bending lengths such that they are greater than a predetermined minimum bending length. As a result, the bast fibers (such as flax stems) have variable lengths and bending lengths greater than a predetermined minimum bending length. Fibers that have bending lengths greater than the predetermined minimum bending length allow complete load transfer from the fibers to the polymer matrix. Fiber lengths produced by conventional scutching/breaking processes are substantially shorter the predetermined minimum bending length and therefore do not allow complete load transfer from the fibers to the polymer matrix.
In some examples, the predetermined minimum bending length is greater than 80 μm. In some examples, the predetermined minimum bending length is greater than 100 μm. In some examples, the predetermined minimum bending length is greater than 230 μm. In some examples, the predetermined minimum bending length is greater than 460 μm. In some examples, the predetermined minimum bending length is in a range from 80 μm to 2 mm. some examples, the predetermined minimum bending length is in a range from 230 μm to 1 mm. For example, the predetermined minimum bending length may be selected using the relationship
where lc is the critical fiber length, d is a fiber diameter, σf is a fiber tensile strength, and τi is the interfacial shear strength. Using typical values of σf (850 MPa), d (18 μm), and τi (33 MPa), the critical length would be 232 μm. In some examples, two times the critical length is used (e.g., 464 μm). These values will differ depending upon the specific fibers and polymer matrix that are used.
The length of the bast fibers typically varies after passing through the roller system. In some examples, the length of bast fibers such as flax fibers can be as high as 30 inches (or perhaps longer) prior to scutching/breaking. After passing through the roller systems described herein, the bast fibers are bent and have bending lengths that are greater than a predetermined minimum bending length. The fibers break at variable lengths so that the fiber is not straight, but the individual bends may still be connected.
In the description that follows,
Referring now to
At 14, retting is performed. Retting involves decomposition of woody matter enclosing the fibers. At 16, scutching/breaking is performed. When the decomposed woody tissue dries, the fibers are fed through rollers of a roller system and crushed. The scutching/breaking process separates the woody matter from the fibers. At 18, combing/heckling is performed to separate coarse fiber bundles from finer bundles and to arrange the fibers generally parallel to one another.
In some examples, the bast fibers are spun into fiber tow or twine at 20. The fiber tow or twine can be used as a reinforcing fiber in a composite. Alternately, the fiber tow or twine can be woven into cloth at 22.
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In some examples, the bast fibers are spun into fiber tow or twine at 20. The fiber tow or twine can be used as a reinforcing fiber in a composite. Alternately, the fiber tow or twine can be woven into cloth at 22.
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In
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In some examples, each of the first plurality of teeth 314-1, 314-2, . . . , and 314-T has rectangular tooth profile. In some examples, each of the plurality of teeth 324-1, . . . , and 324-R has a triangular profile, a rectangular profile, or another suitable tooth profile. One of the first plurality of teeth 314-1, 314-2, . . . , and 314-T is aligned or centered between an adjacent pair of the second plurality of teeth 324-1, . . . , and 324-R.
In some examples, the bast stems have a diameter in a range from 0.5 to 3 mm. A span s between the plurality of teeth 324-1, . . . , and 324-R is in a range from 4 to 7 times the thickness/diameter of the bast stems. In other words, the span is in a range from 2 mm to 21 mm.
In some examples, the bast stems have a diameter in a range from 2 to 3 mm. A span s between the plurality of teeth 324-1, . . . , and 324-R is in a range from 4 to 7 times the thickness/diameter of the bast stems. In other words, the span is in a range from 8 mm to 21 mm. The roller system 300 in
In
The roller systems described herein control bending locations of the bast fiber (such as a flax stem) to a length greater than the predetermined minimum bending length required for use in semi-structural and structural composites. In some examples, the predetermined minimum bending length is greater than 80 μm. In some examples, the predetermined minimum bending length is greater than 100 μm. In some examples, the predetermined minimum bending length is greater than 230 μm. In some examples, the predetermined minimum bending length is greater than 460 μm. In some examples, the predetermined minimum bending length is in a range from 100 μm to 2 mm. some examples, the predetermined minimum bending length is in a range from 230 μm to 1 mm.
Using a shearing process, the fiber bundle is loaded under different conditions that use a lower energy shearing failure mode to separate the fiber bundle from the stem. The fiber bending length dictates the mechanical bending/breaking process and gear tooth spacing for the roller system for bast fibers. Furthermore, the roller systems according to the present disclosure use a shear mode to drive extraction of fiber bundles from woody stems as opposed to a bending failure mode.
Referring now to
In some examples, each of the first plurality of teeth 414-1, 414-2, . . . , and 414-T has a “W”-shaped cross section (including a pair of adjacent triangular tooth sub-portions). Each of the first plurality of teeth 424-1, . . . , and 414-R has a “W”-shaped profile, a triangular profile, a rectangular profile, or another suitable tooth profile. One of the first plurality of teeth 414-1, 414-2, . . . , and 414-T is aligned or centered between an adjacent pair of the second plurality of teeth 424-1, . . . , and 414-R.
In
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In some examples, the continuous reinforcing fibers 554 are positioned by a robot and stitched onto a backing sheet in a predetermined pattern and/or density using tailored fiber placement (TFP). TFP uses a computer numerical controlled robot to stitch the fiber tows or twine onto a backing sheet using stitches. After the fiber tows or twine are attached, the backing sheet and fiber tows are encapsulated in polymer. In
In
Referring now to
While the foregoing examples described the use of bast fibers in the polymer matrix, the bast fibers can be comingled with other types of reinforcing fibers that are not bast fibers (e.g., such as carbon fibers, glass fibers, etc.).
The foregoing description is merely illustrative in nature and is in no way intended to limit the disclosure, its application, or uses. The broad teachings of the disclosure can be implemented in a variety of forms. Therefore, while this disclosure includes particular examples, the true scope of the disclosure should not be so limited since other modifications will become apparent upon a study of the drawings, the specification, and the following claims. It should be understood that one or more steps within a method may be executed in different order (or concurrently) without altering the principles of the present disclosure. Further, although each of the embodiments is described above as having certain features, any one or more of those features described with respect to any embodiment of the disclosure can be implemented in and/or combined with features of any of the other embodiments, even if that combination is not explicitly described. In other words, the described embodiments are not mutually exclusive, and permutations of one or more embodiments with one another remain within the scope of this disclosure.
Spatial and functional relationships between elements (for example, between modules, circuit elements, semiconductor layers, etc.) are described using various terms, including “connected,” “engaged,” “coupled,” “adjacent,” “next to,” “on top of,” “above,” “below,” and “disposed.” Unless explicitly described as being “direct,” when a relationship between first and second elements is described in the above disclosure, that relationship can be a direct relationship where no other intervening elements are present between the first and second elements, but can also be an indirect relationship where one or more intervening elements are present (either spatially or functionally) between the first and second elements. As used herein, the phrase at least one of A, B, and C should be construed to mean a logical (A OR B OR C), using a non-exclusive logical OR, and should not be construed to mean “at least one of A, at least one of B, and at least one of C.”
In the figures, the direction of an arrow, as indicated by the arrowhead, generally demonstrates the flow of information (such as data or instructions) that is of interest to the illustration. For example, when element A and element B exchange a variety of information but information transmitted from element A to element B is relevant to the illustration, the arrow may point from element A to element B. This unidirectional arrow does not imply that no other information is transmitted from element B to element A. Further, for information sent from element A to element B, element B may send requests for, or receipt acknowledgements of, the information to element A.
