Thermoplastic composite material, process for its preparation, composite structures made thereof and process for preparing composite structures

1. A thermoplastic composite material comprising:

(i) a thermoplastic matrix, and

(ii) a fibrous material impregnated with the thermoplastic matrix, wherein

the fibrous material comprises at least 20 wt. %, relative to the total weight of the thermoplastic composite material, of carbon fibers with a weight average aspect ratio of length divided by diameter (L/D) of at least 500; and wherein

the thermoplastic matrix comprises a thermoplastic polymer and 0.01-2 wt. %, relative to the total weight of the thermoplastic composite material, of a laser absorbing additive, and wherein

the thermoplastic composite material is a tape comprising at least a layer comprising unidirectionally oriented continuous carbon fibers.

2. The thermoplastic composite material according to claim 1 , wherein the composite material is a tape having a thickness in the range of 50 μm-1000 μm, and/or having a width in the range of 5 mm-50 cm.

3. The thermoplastic composite material according to claim 1 , wherein the thermoplastic polymer comprises a thermoplastic polyamide.

4. The thermoplastic composite material according to claim 1 , wherein the laser absorbing additive comprises carbon black.

5. The thermoplastic composite material according to claim 1 , wherein the thermoplastic polymer comprises a semi-crystalline semi-aromatic polyamide.

6. A process for the preparation of the thermoplastic composite material according to claim 1 , comprising steps of:

(i) providing the fibrous material comprising the carbon fibers;

(ii) providing a melt of a thermoplastic composition comprising the thermoplastic polymer and the laser absorbing additive;

(iii) impregnating the fibrous material with the melt thereby obtaining an impregnated material; and

(iv) cooling the impregnated material and solidifying the melt to thereby form the thermoplastic composite material.

7. A process for preparing a thermoplastic composite structure, comprising an assembly step which comprises consolidating at least a first piece of the thermoplastic composite material according to claim 1 onto a second piece of a second material.

8. The process according to claim 7 , wherein the second material is a thermoplastic composite material, identical to or different from the thermoplastic composite material in the first piece.

9. The process according to claim 7 , wherein the step of consolidating the first and second pieces is done by at least partially heating or welding.

10. The process according to claim 7 , wherein the step of consolidating the first and second pieces is done by laser welding.

11. The process according to claim 7 , wherein the step of consolidating the first and second pieces is done by nip-laser welding.

12. The process according to claim 7 , wherein the first piece is a piece of a tape, optionally wrapped or wound around the second piece.

13. The process according to claim 12 , further comprising the steps of:

(a) winding the tape such that successive windings of the tape partially overlap with each other at overlapping areas;

(b) consolidating the overlapping areas of the tape thereby creating a hollow body; and

(c) cooling the hollow body to become solid.

14. A composite structure comprising a first piece comprising the thermoplastic composite material according to claim 1 consolidated onto a second piece of a second material.

15. The composite structure according to claim 14 , wherein the first and second pieces have been consolidated by laser welding.

16. The composite structure according to claim 14 , wherein the composite structure is a hollow body, a hollow pipe or a 3-dimensional part comprising a core part made of a plastic material and local reinforcement elements made of a thermoplastic composite material consolidated on the core part.

17. A process for the preparation of a composite tape material, comprising the steps of:

(i) providing unidirectional continuous fibers, and

(ii) impregnating the fibers with a thermoplastic material, wherein

the unidirectional continuous fibers comprise carbon fibers and the thermoplastic material comprises a semi-aromatic polyamide and a laser absorbing additive dispersed in the semi-aromatic polyamide.