Modification Of Carbon Fiber And The Mechanical Properties Of Composite Material For Vehicle

Carbon fiber has become the most important reinforcing material for resin matrix composites in recent years for its characteristics of excellent properties such as high specific strength, high specific modulus, low temperature resistance, high quality and light weight. Its composite materials have been widely used in aerospace, rail transportation, sports equipment and other fields. However, the surface of carbon fiber is hydrophobic, which had defects of small specific surface area, little activity specific surface area, few number of surface active carbon atoms and low surface energy, hence surface modification of carbon fiber is needed. Electropolymerization was adopted to modified carbon fiber, polymer layers were introduced to carbon fiber surface with cyclic voltammetry scans, by using acrylic acid, acrylamide, caprolactam and aniline as monomer respectively.Three electrode system was employed in electropolymerization experiment, which working electrode was carbon fiber, counter electrode was platinum electrode and reference electrode was saturated calomel electrode. When scan potential range was-1V~1V, initial scanning potential was-1V, scan rate was 0.1V/s, sensitivity was 10-3A/V, the optimum concentration of modified monomer and number of cycles were obtained respectively under the condition of 0.3mol/L acrylic acid cycling 15 times, 0.2mol/L acrylamide cycling 5 times, 0.1mol/L caprolactam cycling 10 times and 0.2mol/L aniline cycling 10 times.FT-IR results showed that the characteristic absorption peak of COOH in acrylic acid was appeared nearby 2680cm-1, a weak bending vibration absorption peak of NH in acrylamide was appeared between1680 and 1650cm-1, series variable angle vibration absorption peak of NH2 in caprolactam were appeared at 1650, 1630 and 1590cm-1, several stretching vibration absorption peak of C-N in aniline were appeared at 1340, 1315 and 1265cm-1 respectively. Energy spectrum test results indicated that O content of carbon fiber surface increased by 15.96%, 9.36%, 1.69% and 4.09%, N content of carbon fiber modified by aniline increased by 1.68%.The surface morphology of carbon fiber was observed by SEM test, which founded that acrylic acid products were disc-like particles dispersed uniformly, partial polymer products were united; acrylamide products were formed by small particles, product quantity was less and dispersed inhomogeneous; caprolactam product were massive particles, partial region appeared layered products which coated on the surface of carbon fiber; aniline products were short rod like which distributed uniformly on the surface of carbon fiber, the thickness of the polymer layers were uniform and combined closely.Carbon fiber/epoxy resin composite was prepared by E-51 epoxy resin and polyamide resin with 2:1(quality ratio), adding carbon fiber modified by different conditions to composite which addition of carbon fiber was 5%(volume fraction). Mechanical property test results indicated that ILSS were increased from 10.50 MPa to 23.44, 15.56, 26.96 and 42.66 MPa respectively, increasing by the rate of 48.21, 123.21, 156.70 and 306.25% respectively respectively.