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.
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.
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. https://doi.org/10.1002/pc.22501
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.
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.
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. https://doi.org/10.1016/0266-3538(95)00061-5
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.
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.
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.
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.
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.