Process for manufacturing composite articles, and composite articles made thereby
The present disclosure relates to a process for manufacturing composite articles, and composite articles made thereby. The processes described herein make use of curable compositions containing NCF fabrics having certain types of stitching yarns. The curable compositions and composite articles made according to the present disclosure are particularly suited to the production of composite parts for use in many applications, such as in aviation, automotive, and marine applications.
1 . A process for manufacturing a composite article, the process comprising:
a) providing a curable composition, the curable composition comprising a matrix resin and a non-crimp fabric comprising at least one layer of unidirectionally oriented multifilament carbon yarns and a multifilament stitching yarn interlinking the multifilament carbon yarns, wherein the multifilament stitching yarn comprises a thermoplastic polymer and has a linear density of less than or equal to 80 dtex;
b) heating the curable composition to a temperature T 1 , wherein T 1 is greater than a melting temperature (T m ) of the multifilament stitching yarn and wherein a conversion of the matrix resin at T m or at T 1 is less than or equal to 30%; and
c) maintaining the temperature T 1 or heating to a temperature T 2 for a time sufficient for the curable composition to be cured, thereby manufacturing the composite article.
2 . The process according to claim 1 , wherein the time sufficient for the curable composition to be cured is less than or equal to 6 hours.
3 . The process according to claim 1 , wherein the melting temperature of the multifilament stitching yarn is less than or equal to 230° C.
4 . The process according to claim 1 , wherein the melting temperature of the multifilament stitching yarn is from 70° C. to 200° C.
5 . The process according to claim 1 , wherein the multifilament stitching yarn comprises one or more thermoplastic fibers or filaments.
6 . The process according to claim 1 , wherein the thermoplastic polymer of the multifilament stitching yarn is a polymer selected from the group consisting of polyesters, polyamides, polyimides, polycarbonates, polyurethanes, and copolymers thereof.
7 . The process according to claim 1 , wherein the linear density of the multifilament stitching yarn is in a range of 1 to 55 dtex.
8 . The process according to claim 1 , wherein the non-crimp fabric is multiaxial and comprises more than one layer of unidirectionally oriented multifilament carbon yarns.
9 . The process according to claim 1 , wherein the non-crimp fabric further comprises a veil.
10 . The process according to claim 1 , wherein heating the curable composition to the temperature T 1 comprises heating the curable composition at a ramp rate of about 10° C./min or less.
11 . The process according to claim 1 , wherein heating the curable composition to the temperature T 1 comprises heating the curable composition at a ramp rate from 0.2 to 10° C./min.
12 . The process according to claim 1 , wherein the temperature T 1 is a cure temperature of the curable composition.
13 . The process according to claim 1 , wherein the T m of the multifilament stitching yarn is less than a temperature (T gel ) at which the curable composition gels.
14 . The process according to claim 1 , wherein the curable composition is provided at an infusion temperature and T 1 is greater than both the infusion temperature and the T m of the multifilament stitching yarn.
15 . The process according to claim 1 , wherein the thermoplastic polymer of the multifilament stitching yarn is a semi-crystalline polymer.
16 . The process according to claim 1 , wherein the matrix resin comprises epoxy resin.
17 . The process according to claim 1 , wherein the multifilament stitching yarn of the non-crimp fabric and the matrix resin interdiffuse during the process such that there are little or no areas having only the chemical character of the multifilament stitching yarn.
18 . The process according to claim 1 , wherein the composite article manufactured exhibits a reduction in microcracking relative to a composite article made with stitching yarn not comprising a thermoplastic polymer and a linear density of less than or equal to 80 dtex.
19 . A composite article manufactured according to the process of claim 1 .
20 . A composite article made by a process comprising:
a) providing a curable composition, the curable composition comprising a matrix resin and a non-crimp fabric comprising at least one layer of unidirectionally oriented multifilament carbon yarns and a multifilament stitching yarn interlinking the multifilament carbon yarns, wherein the multifilament stitching yarn comprises a thermoplastic polymer and has a linear density of less than or equal to 80 dtex;
b) heating the curable composition to a temperature T 1 , wherein T 1 is greater than a melting temperature (T m ) of the multifilament stitching yarn and wherein a conversion of the matrix resin at T m or at T 1 is less than or equal to 30%; and
c) maintaining the temperature T 1 or heating to a temperature T 2 for a time sufficient for the curable composition to be cured.