OJCM  Vol.7 No.4 , August 2017
Improvement of Bending Strength of Carbon Fiber/Thermoplastic Epoxy Composites
—Effects of Molecular Weight of Epoxy on Carbon Fiber/Matrix Interfacial Strength and Connection of Cracks in Matrix
Abstract: The bending strength of carbon fiber/thermoplastic epoxy composites (CF/TP-EP Compo.) had bi-linear increasewith increase of weight-average molecular weight (Mw) of matrix. The transition in the bending strength appeared at around 55k of Mw (k means 103). SEM observation of fractured surface of CF/TP-EP Compo. showed that the fracture mode changed from interfacial failure to fiber breakage dominated failure. The smooth surface of carbon fibers appeared at lower Mw than 55k while some resin remained on the fibers indicating good adhesion between carbon fiber and matrix at higher Mw than 55k. The interfacial shear strength between carbon fiber and matrix bi-linearly increased with an increase of Mw similarly to the bending strength of the composite, measured by the micro droplet test. The dynamic loss tanδ of the matrix measured at 2 Hz also showed a bi-linear relationship with respect to Mw having a knee point at Mw = 55k. The connection probability of two cracks introduced on each side of specimens also confirmed that the interfacial strength between carbon fiber and matrix is the key for the mechanical performance of CF/TP-EP Compo. in bending.
Cite this paper: Nishida, H. , Okubo, K. , Fujii, T. , Carvelli, V. (2017) Improvement of Bending Strength of Carbon Fiber/Thermoplastic Epoxy Composites
—Effects of Molecular Weight of Epoxy on Carbon Fiber/Matrix Interfacial Strength and Connection of Cracks in Matrix. Open Journal of Composite Materials, 7, 207-217. doi: 10.4236/ojcm.2017.74014.

[1]   Erber, A. and Spitko, S. (2014) Expanded Role for Thermoplastic Composites, Reinforced Plastics, 58, 29-33.

[2]   Brady, P. and Brady, M. (2007) Automotive Composites: Which Way Are We Going? Reinforced Plastics, 51, 32-35.

[3]   Brady, M. and Brady, P. (2007) Automotive Composites—the Search for Efficiency, Value and Performance. Reinforced Plastics, 51, 26-29.

[4]   Stewart, R. (2010) Automotive Composites Offer Lighter Solutions. Reinforced Plastics, 54, 22-28.

[5]   Marsh, G. (2013) Composites Poised to Transform Airline Economics. Reinforced Plastics, 57, 18-24.

[6]   Klimke, J. and Rothmann, D. (2010) Carbon Composite Materials in Modern Yacht Building. Reinforced Plastics, 54, 24-27.

[7]   Brady, M. and Brady, P. (2010) Technology Developments in Automotive Composites. Reinforced Plastics, 54, 25-29.

[8]   Liu, B., Xu, A. and Bao, L. (2015) Preparation of Carbon Fiber-Reinforced Thermoplastics with High Fiber Volume Fraction and High Heat-Resistant Properties. Journal of Thermoplastic Composite Materials, 30, 724-737.

[9]   Xu, A., Bao, L., Nishida, M. and Yamanaka, A. (2013) Molding of PBO Fabric Reinforced Thermoplastic Composite to Achieve High Fiber Volume Fraction. Polymer Composites, 34, 953-958.

[10]   Chen, J.H., Schulz, E., Bohse, J. and Hinrichsen, G. (1999) Effect of Fiber Content on the Interlaminar Fracture Toughness of Unidirectional Glass/Fiber Polyamide Composite. Composites: Part A, 30, 747-755.

[11]   Mohanty, A.K., Drzal, L.T. and Misra, M. (2002) Engineered Natural Fiber Reinforced Polypropylene Composites Influence of Surface Modifications and Novel Powder Impregnation Processing. Journal of Adhesion Science and Technology, 16, 999-1015.

[12]   Long, A.C., Wilks, C.E. and Rudd, C.D. (2001) Experimental Characterization of the Consolidation of a Commingled Glass/Polypropylene Composite. Composites Science and Technology, 61, 1591-1603.

[13]   Ye, L., Friedrich, K., Kastel, J. and Mai, Y. (1995) Consolidation of Unidirectional CF/PEEK Composites from Commingled Yarn Prepreg. Composites Science and Technology, 54, 349-358.

[14]   Ben, G. and Sakata, K. (2015) Fast Fabrication Method and Evaluation of Performance of Hybrid FRTPs for Applying Them to Automotive Structural Members. Composite Structures, 133, 1160-1167.

[15]   Hirabayashi, A., Ben, G. and Ozeki, H. (2013) Heat Resistance Properties of FRTP Composed of In-Situ Polymerization PA6 and CF and GF Fabrics. Proceedings of 19th International Conference on Composite Materials, Montreal, 23 July-2 August 2013, 1581-1588.

[16]   Nishida, H. (2015) The Development of Thermoplastic Epoxy Resin and Continuous Fiber Reinforced Thermoplastics Using it. Journal of the Adhesion Society of Japan, 51, 516-523.

[17]   Imanishi, T., Nishida, H., Hirayama, N. and Tomomitsu, N. (2007) In Situ Polymerizable Thermoplastic Epoxy Resin and High Performance FRTP Using It and Fiber Fabrics. Proceedings of 16th International Conference on Composite Materials, Kyoto, 8-13 July 2007, 194-195.

[18]   Nishida, H. (2011) Aiming to Create Novel Composites. Journal of the Adhesion Society of Japan, 47, 361-368.

[19]   Nagai, K., Nishida, H., Okubo, K. and Fujii, T. (2016) Static and Fatigue Bending Properties of CFRTP with Highly Polymerized Thermo-Plastic Epoxy for Matrix. Proceedings of the 10th Asian-Australasian Conference on Composite Materials, Busan, 16-19 October 2016, File.T15-3.

[20]   Jensen, M.K., Bach, A., Hassager, O. and Skov, A.L. (2009) Linear Rheology of Cross Linked Polypropylene Oxide as a Pressure Sensitive Adhesive. International Journal of Adhesion & Adhesives, 29, 687-669.