Patent Application
20240246302
The present specification generally relates to methods for joining unidirectional tapes.
Unidirectional tapes are often used in combination with automated fiber placement (AFP) process. The unidirectional tapes may be supplied in spools of several lbs per roll. The unidirectional tapes may be connected by overlapping a certain length at an end and fusing the unidirectional tapes together by heat. This connection is called a splice. When layering the unidirectional tapes having a splice, a location of the splice may become a defect point, especially when the location of the splice is in a close vicinity of a splice of another layer of the unidirectional tapes. The splices in close proximity may cause a thickness of a spliced area where the splices are located to be greater than other areas because the unidirectional tapes are overlapped to each other. Differences in thickness may create a kink and/or buckling in a thickness direction.
In one embodiment, a method for joining unidirectional tapes is provided. The method includes placing a plurality of unidirectional tapes by abutting without overlapping an end of one of the unidirectional tapes with an end of other one of the unidirectional tapes at a butt joint. The unidirectional tapes includes a resin material and a plurality of fibers running in a running direction. The method further includes placing a prepreg including a resin material and a plurality of short fibers over the butt joint to cover an area surrounding the butt joint such that the short fibers run in the running direction. The method further includes fusing the prepreg by applying heat such that the short fibers are fused into a matrix of the unidirectional tapes at the butt joint.
These and additional features provided by the embodiments described herein will be more fully understood in view of the following detailed description, in conjunction with the drawings.
The embodiments set forth in the drawings are illustrative and exemplary in nature and not intended to limit the subject matter defined by the claims. The following detailed description of the illustrative embodiments can be understood when read in conjunction with the following drawings, where like structure is indicated with like reference numerals and in which:
Referring now to
In embodiments, the end 111 of the unidirectional tape 110 and the end 121 of the unidirectional tape 120 have the same shape. For example, the end 111 and the end 121 may be cut straight in a direction perpendicular to a longitudinal direction of the unidirectional tapes 110, 120. The end 111 may be aligned with the end 121 such that to create no overlaps between the unidirectional tapes 110, 120 at the butt joint 130. In embodiments, the butt joint 130 may have a gap about 0.2 mm or less. The gap may be about 0.1 mm or less. In embodiments, the butt joint 130 does not have a gap. For example, the end 111 and the end 121 may touch at respective edges of the end 111 and the 121 in the longitudinal direction of the unidirectional tapes 110, 120.
The unidirectional tapes 110, 120 include a resin material and a plurality of fibers running in a running direction R (e.g., the longitudinal direction of the unidirectional tapes 110, 120). In embodiments, the resin material of the unidirectional tapes 110, 120 may be any material that is either thermoset or thermoplastics. For example, the resin material of the unidirectional tapes 110, 120 may be epoxy, silicone, polyurethane, polyester, vinyl ester, polyimide, urethane, nylon, phenolic, or the like. Also, for example, the resin material of the unidirectional tapes 110, 120 may be polyetherimide (PEI), polyetheretherketone (PEEK), polyamide-imide (PAI), polycarbonate (PC), or the like. The resin material of the unidirectional tapes 110, 120 may be a combination of any of the thermoset or thermoplastics. Above examples of the resin material are non-limiting.
In embodiments, the fibers of the unidirectional tapes 110, 120 may be carbon fibers, which may be polyacrylonitrile (PAN)-based carbon fibers, for example. The carbon fibers may exhibit a fiber modulus of about 33 to 34 million pounds per square inch (msi) or slightly higher. In embodiments, the fibers of the unidirectional tapes 110, 120 may be glass, Kevlar®, carbon, glass comingled, or the like. The fibers of the unidirectional tapes 110, 120 may be aligned in the running direction R.
In embodiments, a basis weight of the unidirectional tapes 110, 120 may be about 50 to 200 grams per square meter. The basis weight of the unidirectional tapes 110, 120 may be about 100 grams per square meter.
A prepreg 140 is placed over the butt joint 130 to cover an area surrounding the butt joint 130. In embodiments, the prepreg 140 may have a width (e.g., the width in a direction perpendicular to the running direction R) sufficient to cover the area surrounding the butt joint 130. For example, the width of the prepreg 140 may be substantially the same as a width of the unidirectional tapes 110, 120. In embodiments, the prepreg 140 may have a length (e.g., the length in the running direction R) sufficient to cover the area surrounding the butt joint 130. For example, the length of the prepreg 140 may be about ¼ inch. The length may be less than ¼ inch. For example, the length may be about ⅛ inch. In embodiments, the prepreg 140 may have a thickness of about 150 μm or less. The thickness of the prepreg 140 may be about 100 μm or less. The prepreg 140 may be a short fiber clef that includes unidirectionally aligned short fibers and resin powder. The short fiber clef may be heated to melt the resin powder to tack the short fibers together for the handling purpose.
The prepreg 140 includes a resin material and a plurality of fibers running in the running direction R. For example, the prepreg 140 is a fiber prepreg impregnated with a resin matrix. In embodiments, the resin material of the prepreg 140 may be any material that is either thermoset or thermoplastics. For example, the resin material of the prepreg 140 may be epoxy, silicone, polyurethane, polyester, vinyl ester, polyimide, urethane, nylon, phenolic, or the like. Also, for example, the resin material may be polyetherimide (PEI), polyetheretherketone (PEEK), polyamide-imide (PAI), polycarbonate (PC), or the like. The resin material of the prepreg 140 may be a combination of any of the thermoset or thermoplastics. The prepreg 140 may be impregnated above examples of the resin material of the prepreg 140 are non-limiting.
In embodiments, the fibers of the prepreg 140 may be short fibers. The fibers of the prepreg 140 may be carbon fibers, which may be polyacrylonitrile (PAN)-based carbon fibers, for example. The carbon fibers of the prepreg 140 may exhibit a fiber modulus of about 33 to 34 million pounds per square inch (msi) or slightly higher. In embodiments, the fibers of the prepreg 140 may be glass, Kevlar®, carbon, glass comingled, or the like. In embodiments, only the fibers of the prepreg 140 impregnate in between the fibers of the unidirectional tapes 110, 120.
In embodiments, a basis weight of the prepreg 140 may be about 5 to 40 grams per square meter. The basis weight of the prepreg 140 may be about 8 to 10 grams per square meter. In embodiments, a volume ratio of the resin material may be about 50% and a volume ratio of the fiber may be about 50%. The volume ratio of the resin material may be less than the volume ratio of the fiber. For example, the volume ratio of the resin material may be about 40% and the volume ratio of the fiber may be about 60%. The significantly low weight and volume of the prepreg 140 may allow the total weight and volume at the butt joint 130 to be within a deviation range of the unidirectional tapes 110, 120 when the prepreg 140 is impregnated into the unidirectional tapes 110, 120, which may enable to avoid thickness and width increases of the unidirectional tapes 110, 120.
In embodiments, the resin material of the unidirectional tapes 110, 120 may be the same as the resin material of the prepreg 140. In embodiments, the resin material of the unidirectional tapes 110, 120 may be different from the resin material of the prepreg 140. In embodiments, the resin material of the unidirectional tape 110 may be different from the resin material of the unidirectional tape 120.
Referring to
In embodiments, the end 211 of the unidirectional tape 210 and the end 221 of the unidirectional tape 220 have the same shape. In embodiments, the end 211 of the unidirectional tape 210 and the end 221 of the unidirectional tape 220 may be cut in a shape including a diagonal portion. For example, the end 211 and the end 221 are cut diagonally with respect to a longitudinal direction of the unidirectional tapes 110, 120. In embodiments, the shape may include a V shape, a W shape, a zigzag shape, or the like. The shape may be symmetrical or asymmetrical.
The end 211 may be aligned with the end 221 such that to create no overlaps between the unidirectional tapes 210, 220 at the butt joint 230. In embodiments, the butt joint 230 may have a gap about 0.2 mm or less. The gap may be about 0.1 mm or less. In embodiments, the butt joint 230 does not have a gap. For example, the end 211 and the end 221 may touch at respective edges of the end 211 and the 221 in the longitudinal direction of the unidirectional tapes 210, 220.
The unidirectional tapes 210, 220 include a resin material and a plurality of fibers running in a running direction R (e.g., the longitudinal direction of the unidirectional tapes 210, 220). Unless noted otherwise, the configurations of the unidirectional tapes 210, 220 including materials are the same as those described in the embodiments of the splice 100, thereby omitted detailed descriptions.
A prepreg 240 is placed over the butt joint 230 to cover an area surrounding the butt joint 230. In embodiments, the prepreg 240 may have a width (e.g., the width in a direction perpendicular to the running direction R) sufficient to cover the area surrounding the butt joint 230. For example, the width of the prepreg 240 may be substantially the same as a width of the unidirectional tapes 210, 220. In embodiments, the prepreg 240 may have a length (e.g., the length in the running direction R) sufficient to cover the area surrounding the butt joint 230. For example, the length of the prepreg 240 may be sufficient to cover an area surrounding the diagonal end 211 of the unidirectional tape 210 and the diagonal end 221 of the unidirectional tape 220. For example, the length of the prepreg 240 may be sufficient to cover a longitudinal length of the diagonal end 211 of the unidirectional tape 210 and the diagonal end 221 of the unidirectional tape 220. In embodiments, the prepreg 240 may have a thickness of about 150 μm or less. The thickness of the prepreg 240 may be about 100 μm or less.
The prepreg 240 includes a resin material and a plurality of fibers running in the running direction R. Unless noted otherwise, the configurations of the prepreg 240 including materials are the same as those described in the embodiments of the prepreg 140, thereby omitted detailed descriptions.
Referring to
In embodiments, the short fibers of the prepreg 140 may be fused into the matrix of the unidirectional tapes 110, 120 at the butt joint 130 such that a thickness of the joined unidirectional tapes is not greater than a thickness of the unidirectional tapes 110, 120. In embodiments, the thickness of the joined unidirectional tapes may be substantially the same as the thickness of the unidirectional tapes 110, 120. During fusing, the short fibers of the prepreg 140 may be moved to be positioned between the fibers of the unidirectional tapes 110, 120. The resin of the prepreg 140 may be spread over the area surrounding the butt joint 130. The short fibers of the prepreg 140 may be aligned in the running direction R. Therefore, the short fibers of the prepreg 140 and the fibers of the unidirectional tapes 110, 120 may be aligned in the same direction (e.g., the running direction R).
Referring to
It is noted that the terms “substantially” and “about” may be utilized herein to represent the inherent degree of uncertainty that may be attributed to any quantitative comparison, value, measurement, or other representation. These terms are also utilized herein to represent the degree by which a quantitative representation may vary from a stated reference without resulting in a change in the basic function of the subject matter at issue.
While particular embodiments have been illustrated and described herein, it should be understood that various other changes and modifications may be made without departing from the spirit and scope of the claimed subject matter. Moreover, although various aspects of the claimed subject matter have been described herein, such aspects need not be utilized in combination. It is therefore intended that the appended claims cover all such changes and modifications that are within the scope of the claimed subject matter.
