Method for fabricating composite fasteners

Patent metadata

Field	Value
Publication number	US-9623612-B2
Application number	US-201313773042-A
Country	US
Kind code	B2
Filing date	Feb 21, 2013
Priority date	Feb 21, 2013
Publication date	Apr 18, 2017
Grant date	Apr 18, 2017

Abstract

Composite fasteners have a high fraction of discontinuous, randomly oriented reinforcing fibers. A charge of thermoplastic fiber flakes are heated to melting temperature within a reservoir, flowed into multiple mold cavities and compression molded. The molded fasteners have high strength, exhibit quasi-isotropic properties and may be produced in high volume.

First claim

What is claimed is:

1. A method of producing a composite fastener, comprising:
introducing thermoplastic resin infused fiber flakes into a reservoir;
heating the infused fiber flakes in the reservoir to the melting temperature of the thermoplastic resin, resulting in a mixture of melted thermoplastic resin and fiber flakes; and,
flowing the mixture of the melted thermoplastic resin and fiber flakes into a mold having the shape of the fastener.

2. The method of claim 1 , further comprising;
providing a fiber pre-preg having a relatively high fiber content, and
chopping the fiber pre-preg into the infused fiber flakes.

3. The method of claim 2 , wherein the fiber pre-preg includes unidirectional reinforcing fibers forming at least approximately 60% by volume of the pre-preg.

4. The method of claim 2 , wherein the fiber pre-preg includes bidirectional reinforcing fibers.

5. The method of claim 1 , further comprising:
measuring a charge of the infused fiber flakes to be introduced into the reservoir, wherein the charge corresponds to a volume when melted that substantially matches the volume of a plurality of mold cavities in the mold.

6. The method of claim 1 , further comprising:
compressing melted thermoplastic resin and the infused fiber flakes in the mold.

7. The method of claim 1 , wherein flowing the mixture into the mold includes randomly orienting the fiber flakes in the mixture.

8. A method of producing fiber reinforced thermoplastic fasteners, comprising:
producing thermoplastic resin infused fiber flakes;
placing a charge of the infused fiber flakes into a reservoir;
heating the infused fiber flakes within the reservoir until resin in the infused fiber flakes melt and become a flowable mixture of thermoplastic resin and fibers;
flowing the flowable mixture from the reservoir into each of a plurality of mold cavities in a mold, each of the mold cavities having the shape of a fastener; and,
compression molding the flowable mixture into a plurality of fasteners.

9. The method of claim 8 , wherein producing the infused fiber flakes is performed by cutting fiber pre-preg.

10. The method of claim 9 , wherein cutting the fiber pre-preg is performed by chopping strips of unidirectional pre-preg tape.

11. The method of claim 8 , further comprising:
forming a charge of the infused fiber flakes having a volume, when melted, that substantially corresponds to the volume of the mold cavities.

12. The method of claim 8 , wherein flowing the flowable mixture into the mold cavities is performed such that fiber orientations of the fiber flakes are random substantially throughout each of the mold cavities.

13. The method of claim 8 , further comprising:
allowing the fasteners to cool and solidify within the mold cavities; and, removing the fasteners from the mold cavities.

Assignees

• Boeing Co

Inventors

• Bartel Aaron William
• Muntz Nathan A

Classifications

• F16B23/0038

  substantially prismatic with up to six edges, e.g. triangular, square, pentagonal, Allen-type cross-sections · CPC title

• B29K2105/12

  of short lengths, e.g. chopped filaments, staple fibres or bristles · CPC title

• B29C43/52

  Heating or cooling · CPC title

• B29C43/02

  of articles of definite length, i.e. discrete articles {(B29C35/0227 takes precedence)} · CPC title

• B29C43/36

  Moulds for making articles of definite length, i.e. discrete articles · CPC title