High performance light weight carbon fiber fabric-electrospun carbon nanofibers hybrid polymer composites

Abstract

The present disclosure relates to the development of high performance light weight carbon fiber fabric-electrospun carbon nanofibers hybrid polymer composites and a process thereof. In this process continuous carbon nanofiber sheets of diameter in the range of few hundred nanometers are developed from electrospun PAN nanofibers and sandwich between the carbon fiber fabric epoxy resin prepregs to develop hybrid polymer composites by compression molding technique with low content of carbon fibers.

Claims

1. A carbon fiber fabric-carbon nanofiber epoxy resin hybrid polymer composite comprising unidirectionally aligned continuous carbon nanofiber sheet derived from polyacrylonitrile (PAN) based electrospun nanofibers, sandwiched between carbon fiber fabric laminates, wherein the thickness of composite is 2 to 3 mm and contains 302 wt % of carbon fibers.

2. The carbon fiber fabric-carbon nanofiber epoxy resin hybrid polymer composite of claim 1 having a bending strength between 300 to 750 MPa.

3. The carbon fiber fabric-carbon nanofiber epoxy resin hybrid polymer composite of claim 1 having an interlaminar shear strength between 25 to 60 MPa.

4. The carbon fiber fabric-carbon nanofiber epoxy resin hybrid polymer composite of claim 1 having a modulus between 10 to 50 GPa.

5. A process for preparing a carbon fiber fabric-carbon nanofiber epoxy resin hybrid polymer composite as claimed in claim 1, wherein the said process comprises: i. electrospinning 8-12 wt % Polyacrylonitrile (PAN) in an organic solvent at applied voltage 15-20 KV and drum collector speed 2000-3000 rpm for 10-20 hrs followed by stabilizing PAN electrospun nanofiber at 200-300 C. at heating rate 1 to 5 C./min and carbonization of stabilized PAN nanofibers sheets at 800-1000 C. to get continuous carbon nanofiber sheets having diameter in range of 200-300 nm; ii. impregnating carbon fiber fabric with thermosetting epoxy resin and composite is developed by using compression molding technique and thereafter curing at temperature 50-100 C. for a period ranging between 1-3 h to develop carbon fiber polymer composite; and iii. sandwiching carbon nanofiber sheet as obtained in step (i) between carbon fiber fabric impregnated by thermosetting epoxy resin as obtained in step (ii) to prepare the carbon fiber fabric-carbon nanofiber epoxy resin hybrid polymer composite.

6. The process as claimed in claim 5, wherein the organic solvent is selected from the group consisting of N,N-dimethylformamide, N-Methyl-2-pyrrollidone and tetrahydrofuran.

7. The process as claimed in claim 5, wherein the carbon nanofiber content in the carbon fiber-carbon nanofiber epoxy resin hybrid polymer composite varies between 0.5 to 3.0 wt %.

8. A carbon fiber fabric-carbon nanofiber epoxy resin hybrid polymer composite comprising unidirectionally aligned continuous carbon nanofiber sheet derived from polyacrylonitrile (PAN) based electrospun nanofibers, sandwiched between carbon fiber fabric laminates, wherein the thickness of composite is 2 to 3 mm and contains 302 wt % of carbon fibers, wherein the carbon fiber fabric-carbon nanofiber epoxy resin hybrid polymer composite is prepared by a process comprising: i. electrospinning 8-12 wt % Polyacrylonitrile (PAN) in an organic solvent at applied voltage 15-20 KV and drum collector speed 2000-3000 rpm for 10-20 hrs followed by stabilizing PAN electrospun nanofiber at 200-300 C. at heating rate 1 to 5 C./min and carbonization of stabilized PAN nanofibers sheets at 800-1000 C. to get continuous carbon nanofiber sheets having diameter in range of 200-300 nm; ii. impregnating carbon fiber fabric with thermosetting epoxy resin and composite is developed by using compression molding technique and thereafter curing at temperature 50-100 C. for a period ranging between 1-3 h to develop carbon fiber polymer composite; and iii. sandwiching carbon nanofiber sheet as obtained in step (i) between carbon fiber fabric impregnated by thermosetting epoxy resin as obtained in step (ii) to prepare the carbon fiber fabric-carbon nanofiber epoxy resin hybrid polymer composite.

9. The carbon fiber fabric-carbon nanofiber epoxy resin hybrid polymer composite of claim 8 having a bending strength between 300 to 750 MPa.

10. The carbon fiber fabric-carbon nanofiber epoxy resin hybrid polymer composite of claim 8 having an interlaminar shear strength between 25 to 60 MPa.

11. The carbon fiber fabric-carbon nanofiber epoxy resin hybrid polymer composite of claim 8 having a modulus between 10 to 50 GPa.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a SEM micrograph of electrospun continuous PAN copolymer nanofiber and carbon nanofiber sheet derived from PAN copolymer based electrospun nanofibers.

(2) FIG. 2 is a schematic view of a carbon fiber-carbon nanofiber hybrid composite, in which a carbon fiber fabric is indicated by reference numeral 21 and a carbon nanofiber sheet is indicated by reference numeral 22.

(3) FIG. 3 is a micrograph showing carbon fiber distribution and bonding with epoxy resin.

(4) FIG. 4 is a micrograph of a carbon nanofiber sheet on the carbon fiber fabric surface sandwich.

(5) FIG. 5 is a micrograph of the microstructure of a carbon fiber-carbon nanofiber reinforced hybrid polymer composite.

DETAILED DESCRIPTION OF THE INVENTION

(6) In certain aspects, the disclosure relates to the development of high performance light weight carbon fiber fabric-electrospun carbon nanofibers epoxy hybrid polymer composites without increasing bulk density of composite. Generally, carbon fiber polymer composite are being developed with carbon fiber content 30 to 60 wt % and mechanical properties of unidirectional fiber composite are fiber content dependent. Apart from fiber content, mechanical properties of composite depends upon bulk density, properties of fiber and matrix and fiber-matrix interface. While in case of 2D carbon fiber composites, due to axial and transverse mismatch of coefficient of thermal expansion between fiber and matrix, their interactions becomes weak and causes delamination. This delamination substantially reduces load carrying capacity and durability of composites and leads to disastrous structural failure and hence poor mechanical properties of the composite. To improve mechanical properties of 2D composites, in the present invention, nano interfacing approach was adapted.

(7) The electrospun continuous carbon nanofiber sheets were fabricated from electrospun PAN nanofibers converted to carbon nanofiber by subsequent stabilization and carbonization processes.

(8) The 2D carbon fiber fabric thermosetting epoxy polymer composites were developed from 302 wt % of carbon fiber content. The epoxy resin (epoxy resin and hardener triethylenetetramine in the ratio of 100:12.5) content was 702 wt %.

(9) The carbon fiber fabric epoxy resin polymer composites developed by compression molding technique with 302 wt % of carbon fibers gave bending strength of 398 MPa, interlaminar shear strength of 32 MPa and Modulus of 20.6 GPa.

(10) The carbon fiber fabric epoxy polymer hybrid composites developed by sandwiching carbon nanofiber sheet on carbon fiber laminate prepreg by compression molding technique.

(11) The carbon nanofibers of 2 to 8 sheets and size 60 mm12 mm were sandwiched between the carbon fiber fabric preform.

(12) It was found that carbon nanofibers sheets in the range of 0.5 to 3.0 weight % sandwich between the carbon fiber fabric laminates in the hybrid polymer composite gives maximum bending strength of 730 MPa, interlaminar shear strength of 56.8 MPa and modulus of 43 GPa.

(13) The hybrid polymer composite with 1.1 wt % of carbon nanofibers gives the maximum properties. It increases bending strength by 175%, interlaminar shear strength by 190% and modules by 200% as compared to control composite with 302 wt % of high strength carbon fiber fabric without carbon nanofibers.

(14) The present invention relates in certain aspects to the development of high performance light weight carbon fiber-carbon nanofiber hybrid polymer composite. The processing steps include: a) development of continuous carbon nanofiber sheet from PAN based electrospun nanofibers. b) development of carbon fiber-electrospun carbon nanofibers hybrid polymer composites by compression molding technique with different weight fraction carbon nanofiber sheets. c) Characterization of carbon fiber-electrospun carbon nanofiber hybrid polymer composites for bending strength and interlaminar shear strength. In this investigation the carbon fiber-carbon nanofiber reinforced polymer composites developed by compression molding technique with improved bending strength, modulus and interlaminar shear strength with only carbon fiber content 302 wt % in which carbon nanofiber sheets sandwich between carbon fiber fabric laminates prepreg in different weight fraction ranging from 0.5 to 3.0%. The continuous carbon nanofiber sheets between carbon fiber prepreg reduced the porosity and increased bulk density. The carbon nanofiber sheets improve the mechanical properties of matrix and load transferring ability which is lacking in the 2D carbon fabric composite. The bending strength of carbon nanofiber reinforced composite increases from 400 MPa to 730 MPa, modulus from 21 GPa to 43 GPa and interlaminar shear strength from 32 MPa to 56 MPa. The bending strength value of 730 MPa to be achieved required the carbon fiber fabric content more than 60% in polymer based carbon fiber composite.

EXAMPLES

(15) The following examples are given by way of illustration of the working of the invention in actual practice and therefore should not be construed to limit the scope of the present invention.

Example 1

(16) The polymer having high carbon yield has been taken as source polymer for the synthesis of continuous electrospun polymer nanofiber sheet. The polyacrylonitrile 12 wt % solution was prepared by dissolving in organic solvent (N, N Dimethylformamide) to get spinable solution of weight content 12 wt %. The solution was stirred on magnetic stirrer for 18 h to get uniformly mixture. The prepared solution was electrospun at 0.50 ml/hr at applied voltage 15 KV. Tip to collector distance was kept 20 cm and collector speed 2000 rpm. The collected fibers were continuous on collector.

Example 2

(17) As per Example 1, solution prepared from 12 wt % of polyacrylonitrile (PAN) in N,N Dimethylformamide was electrospun at flow rate of 0.20 ml/hr, tip to collector distance 20 cm and drum collector speed 2000 rpm. Voltage was kept at 15 KV. The continuous polymer nanofibers collected on the collector of diameter from 500-600 nm.

Example 3

(18) As per example 2, PAN based nanofiber sheets are stabilized at 300 C. in oxidizing atmosphere (in Air) at heating rate 2 C./min to get thermally stable nanofiber sheets. The stabilized nanofiber sheet carbonized at 1000 C. and to get carbon nanofibers having diameter less than stabilized nanofibers (200-300 nm).

Example 4

(19) The carbon fiber fabric polymer composites developed with fiber volume fraction 30 wt % and polymeric epoxy resin content 70 wt %. The 2D carbon fiber fabric polymer composite was developed by compression molding technique. The carbon fiber fabric impregnated by thermosetting epoxy resin in which the ratios epoxy resin and hardener was 100:12.5. On the impregnated fabric sheets left for 1 hr at 40 C. to release excess resin and solvent. The impregnated structure was placed in die mold and kept in the hot plate of hydraulic press. At desired temperature of 60 C., pressure 100 Kg/cm.sup.2 was applied and die mold was kept at the temperature 100 C. for 1 hr for complete curing.

(20) Finally the carbon fiber polymer composites possessing 302 wt % of fiber content obtained. The composite have bending strength 398 MPa, interlaminar shear strength 32 MPa and Modulus 20.6 GPa.

Example 5

(21) Carbon fiber polymer composites are developed using 50 wt % of carbon fiber content and epoxy resin content 50%. Same process as per example 4, used for making the composites. The composite have bending strength 540 MPa, interlaminar shear strength 36 MPa and Modulus 40.6 GPa

Example 6

(22) As per Example 4, carbon fiber fabric sheets were impregnated and then sandwiched with continuous carbon nanofiber sheets and left for 1 hr at 40 C. to release excess resin and solvent. The impregnated sandwich structure placed in die mold and kept in the hot plate of hydraulic press. At desired temperature 60 C. and 100 Kg/cm.sup.2 pressure was applied and Lateran die mold kept at the 100 C. for 1 hr for complete curing. Finally, carbon fiber fabric-carbon nanofiber polymer hybrid composites of thickness 2 mm with different weight (0.5 to 3.0%) content of carbon nanofibers were prepared.

Example 7

(23) Carbon fiber fabric epoxy polymer hybrid composites developed by sandwiching carbon nanofiber sheets on carbon fiber laminate prepreg followed by compression molding technique as process mentioned in example 6. It was found that carbon nanofibers sheets 0.6 wt % of the carbon fiber fabric weight at interfaces or sandwich between carbon fiber fabric laminates in the hybrid polymer composites gives maximum bending strength 449 MPa, interlaminar shear strength 51 MPa and modulus 20 GPa.

Example 8

(24) Carbon fibers fabric epoxy polymer hybrid composites developed by sandwiching carbon nanofiber sheet on carbon fiber laminate prepreg and by compression molding technique as process mentioned in example 6. It was found that carbon nanofibers sheets of weight 0.9% of the carbon fiber fabric weight at interface or sandwich between carbon fiber laminates in the hybrid polymer composites gives maximum bending strength 528 MPa, interlaminar shear strength 54 MPa and modulus 31 GPa.

Example 9

(25) Carbon fibers fabric epoxy polymer hybrid composites developed by sandwiching carbon nanofiber sheet on carbon fiber laminate prepreg by compression molding technique as process mentioned in example 6. It found that carbon nanofibers sheets of weight 1.1% of the carbon fiber fabric weight at interface or sandwich between carbon fiber laminates in the hybrid polymer composites gives maximum bending strength 730 MPa, Interlaminar shear strength 56.8 MPa and modulus 43 GPa in which carbon nanofiber content was 1.1 wt %.

Example 10

(26) Carbon fibers fabric epoxy polymer hybrid composites developed by sandwiching carbon nanofiber sheet on carbon fiber laminate prepreg and by compression molding technique as process mentioned in example 6. It found that carbon nanofibers sheets of weight 1.3% of the carbon fiber fabric weight at interface or sandwich between carbon fiber laminates in the hybrid polymer composites gives maximum bending strength 672 MPa, Interlaminar shear strength 49 MPa and modulus 34 GPa.

Example 11

(27) Carbon fibers fabric epoxy polymer hybrid composites developed by sandwiching carbon nanofiber sheet on carbon fiber laminate prepreg and by compression molding technique as process mentioned in example 6. It was found that carbon nanofibers sheets of weight 1.7% of the carbon fiber fabric weight at interface or sandwich between carbon fiber laminates in the hybrid polymer composites gives maximum bending strength 602 MPa, Interlaminar shear strength 46 MPa and modulus 33 GPa.

Example 12

(28) Carbon fibers fabric epoxy polymer hybrid composites developed by sandwiching carbon nanofiber sheet on carbon fiber laminate prepreg and by compression molding technique as process mentioned in example 6. It was found that carbon nanofibers sheets of weight 1.9% of the carbon fiber fabric weight at interface or sandwich between carbon fiber fabric laminates in the hybrid polymer composites gives maximum bending strength 594 MPa, interlaminar shear strength 20 MPa and modulus 31 GPa.

Example 13

(29) Carbon fibers fabric epoxy polymer hybrid composites developed by sandwiching carbon nanofiber sheet on carbon fiber laminate prepreg and by compression molding technique as process mentioned in example 6. It was found that carbon nanofibers sheets of 3.0 wt % of the carbon fiber fabric weight, at interface or sandwich between carbon fiber laminates in the hybrid polymer composites gives maximum bending strength 481 MPa and interlaminar shear strength 27 MPa.

Advantage of the Invention

(30) In certain aspects, various embodiments of the disclosure provide one or more of the following advantages. 1. The light weight hybrid polymer composites developed by incorporating continuous carbon nanofiber sheets between carbon fiber fabric prepreg with only 302 wt % carbon fiber content. 2. Cost effective technique for the development of high performance carbon fiber composite. 3. The light weight composites with enhanced mechanical properties and with reduced defects. 4. Light weight composite has many applications in the areas like aerospace, military, satellite, automobile, sport goods and wind energy as turbine blades etc.