Additive manufacturing of discontinuous fiber composites using magnetic fields

1. A method of producing a composite part, comprising:

(a) introducing a precursor material in a first layer adjacent a build plate, the precursor material comprising a matrix material and magnetically responsive particles, the magnetically responsive particles comprising at least in part a magnetic material;

(b) orienting the magnetically responsive particles in a first alignment with a first magnetic field;

(c) consolidating a first portion of the matrix material in the first layer with the magnetically responsive particles within the first portion held in the first alignment in accordance with a particle alignment pattern for the first layer, by concurrently consolidating a first subset of discrete voxels;

(d) orienting a further portion of the magnetically responsive particles in a further alignment different from the first alignment with a further magnetic field; and

(e) consolidating a further portion of the matrix material in the first layer with the magnetically responsive particles within the further portion held in the further alignment in accordance with the particle alignment pattern for the first layer, by concurrently consolidating a further subset of discrete voxels.

2. The method of claim 1 , further comprising:

(f) repeating steps (d) and (e) until a determined portion of the matrix material in the first layer has been consolidated.

3. The method of claim 1 , wherein in steps (c) and (e), the matrix material is partially cured, fully cured, solidified, polymerized, or cross-linked.

4. The method of claim 1 , further comprising, when a desired portion of the matrix material in the first layer has been consolidated, removing the first layer from the build plate and introducing additional precursor material adjacent the build plate in a second layer and adjacent to the first layer.

5. The method of claim 1 further comprising:

(g) introducing additional precursor material in a second layer adjacent the first layer,

(h) orienting the particles in the second layer in a third alignment with a magnetic field;

(i) consolidating a first portion of the matrix material in the second layer with the magnetically responsive particles within the first portion held in the third alignment;

(j) orienting a further portion of the magnetically responsive particles in a fourth alignment with a magnetic field different from the third alignment;

(k) consolidating a second portion of the matrix material in the second layer to consolidate the matrix material with the magnetically responsive particles within the second portion held in the fourth alignment;

(l) repeating steps (j) and (k) until a desired portion of the matrix material in the second layer has been consolidated.

6. The method of claim 1 , wherein the first and further magnetic fields are applied by one or more magnetic field sources parallel to a plane of the first layer and one or more magnetic field sources out of plane with the first layer.

7. The method of claim 1 , wherein the voxels of the first portion are interspaced with the voxels of the further portion.

8. The method of claim 1 , wherein each voxel has a resolution of at least about 50 ×50 ×50 microns.

9. The method of claim 1 , wherein each layer has a thickness of at least about 50 microns.

10. The method of claim 1 , wherein the magnetic material comprises a ferromagnetic material, a paramagnetic material, a superparamagnetic material, iron oxide, iron, cobalt, nickel, an iron alloy, a cobalt alloy, or a nickel alloy.

11. The method of claim 1 , wherein the magnetic material comprises particles, microbeads, nanoparticles, filings, fibers, flakes, rods, whiskers, or platelets.

12. The method of claim 1 , wherein the magnetically responsive particles comprise a non-magnetic material coupled with the magnetic material.

13. The method of claim 12 , wherein the non-magnetic material comprises aluminum oxide, calcium phosphate, copper, glass, calcium sulfate, nylon, polystyrene, or silicon carbide.

14. The method of claim 12 , wherein the non-magnetic material comprises discontinuous fibers, rods, platelets, flakes, or whiskers.

15. The method of claim 12 , wherein the non-magnetic material is coated with the magnetic material.

16. The method of claim 1 , wherein the magnetically responsive particles are anisotropic in shape in at least one dimension.

17. The method of claim 1 , wherein the magnetically responsive particles have a longest dimension ranging from 200 nm to 1000 μm.

18. The method of claim 17 , wherein the magnetically responsive particles have a longest dimension ranging from 1 μm to 20 μm.

19. The method of claim 1 , wherein the magnetically responsive particles have an aspect ratio ranging from 2 to 200.

20. The method of claim 1 , wherein the matrix material comprises a photopolymer and in step (c) and step (e), the matrix material is cured by illumination of selected voxels of the matrix material with radiation having a wavelength selected to effect a curing of the photopolymer.

21. The method of claim 1 , wherein the radiation source ranges from 300 nm to 900 nm in wavelength.

22. The method of claim 1 , wherein the radiation source ranges from ultraviolet to infrared.

23. The method of claim 1 , wherein the matrix material comprises a photocurable acrylic material, a polymethylmethacrylate (PMMA) material, or a polyurethane material.

24. The method of claim 1 , wherein the matrix material of the precursor material has a viscosity prior to consolidation ranging from 0.7 mPa·s to 10 Pa·s.

25. The method of claim 1 , wherein the precursor material comprises an acrylic based photopolymer and reinforcing aluminum oxide micro-platelet particles labeled with iron oxide nanoparticles.

26. The method of claim 1 , wherein steps (c) and (e) further comprise projecting illumination from a digital light projector on the first subset of discrete voxels and the further subset of discrete voxels respectively.