Chapter 7 Evaluation of the Influence of Water Absorptivity on the Properties of CFRP Cylinder Materials by SHPB Impact Compression Test J. Liu, K. Takeo, and S. Yoneyama Abstract In this study, dynamic compressive behaviors of resin-based CFRP were measured by using split Hopkinson pressure bar tests to consider the effect of water absorption on dynamic mechanical properties. The split Hopkinson pressure bar test method (SHPB method) is used to provide high strain rate. In order to satisfy the experimental equipment needs of SHPB method, cylindrical CFRP material was used for impact compression test. Similar sample with different water absorption rates after several days of continuous water absorption under hygrothermal conditions were used in some of the experiments. This fiber interlayer and resin matrix water absorption will pose a great influence on the strength and strain rate of the material and even the load rate dependency under the compression of the vertical fiber direction. The process of destruction was observed using the experimental mechanics, and the experimental data was evaluated. Keywords SHPB impact compression tester · Water absorption rates · Strength-strain rate dependence 7.1 Background Carbon fiber composites such as Carbon Fiber Reinforced Plastic (CFRP) have higher specific strength, rigidity, and specific gravity compared with general metal and metal composites. Therefore, these materials are currently commonly used in the manufacture of various components of aircraft, such as the wing of the aircraft, the hatch and the cabin casing, etc. Materials used in aircraft are required to have impact resistance and vibration resistance in high humidity environments. CFRP material expands and deforms, generating residual stress and changing the material properties in a high-temperature and humidity environment [1]. FRP materials are often manufactured by Resin Transfer Molding, Sheet Molding Compound, and Autoclave method. However, these methods create small hollow pores between the composite plates during the pressure forming process. The size, shape, and amount of pores have a great effect on mechanical properties such as strength. It is necessary to understand the effect of water absorption on the mechanical properties due to the softening of fiber matrix in the high-temperature and humidity environment [2]. In previous studies, Hironaka and Yamamoto et al. clarified that CFRP plate absorbed for a long time with 373 K of distilled water had improved surface softening and Charpy impact value [3, 4]. Meng et al. conducted a three-point bending test of CFRP laminates in a high-temperature and humidity environment to investigate the effect of pores generated during the forming process on the water absorption of the laminates. In the results, the water absorption has obvious influence on the material strength decline [5]. However, the effect of moisture absorption of resin matrix under dynamic high strain rate was not obtained. The purpose of this study is to analyze the effect of water absorption on the dynamic compression characteristics of CFRP. J. Liu ( ) · K. Takeo · S. Yoneyama ( ) Department of Mechanical Engineering, Aoyama Gakuin University, Sagamihara-city, Kanagawa, Japan e-mail: c5619133@aoyama.jp; takeo@me.aoyama.ac.jp; yoneyama@me.aoyama.ac.jp © The Society for Experimental Mechanics, Inc. 2021 M.-T. Lin et al. (eds.), Advancement of Optical Methods & Digital Image Correlation in Experimental Mechanics, Conference Proceedings of the Society for Experimental Mechanics Series, https://doi.org/10.1007/978-3-030-59773-3_7 61
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