Initiation of kink-band failure of a unidirectional CFRP due to microscale fiber undulation

2022 Fiscal Year Final Research Report

• Project/Area Number: 20K04184
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Review Section: Basic Section 18010:Mechanics of materials and materials-related
• Research Institution: Nihon University
• Principal Investigator: UEDA Masahito 日本大学, 理工学部, 准教授 (80434116)
• Project Period (FY): 2020-04-01 – 2023-03-31
• Keywords: 炭素繊維強化プラスチック / 圧縮強度

Outline of Final Research Achievements

The microscale fiber fluctuations in a unidirectional carbon fiber reinforced plastic (UD CFRP) are the main cause of the low compressive strength in the fiber direction. However, the origin of the longitudinal compressive failure i.e., kink band failure in the microscale fiber fluctuations has not been clarified. In this study, the compressive strength was predicted considering the variability of the fiber misalignment angle. All fibers supported a compressive load in the initial loading. The fibers progressively declined their load-bearing capability in descending order of the misalignment angle with an increase in compressive loading. The fibers with a misalignment angle of 0.5 degree or smaller showed a large load drop after their maximum loading, which triggered the ultimate failure. It was shown that the variability of the fiber misalignment angle was indispensable to determining the axial compressive strength of the UD CFRP.

Free Research Field

材料力学

Academic Significance and Societal Importance of the Research Achievements

炭素繊維強化プラスチック（CFRP）の繊維方向圧縮強度は繊維方向引張強度の50～60%程度であり．曲げを受ける構造部材として使用する場合には圧縮側の補強が必要となる．従って，圧縮強度が向上すれば，CFRP構造の更なる軽量化を実現することができる．本研究では，マイクロスケールの繊維揺らぎを考慮に入れた一方向CFRPの圧縮強度予測方法を確立することによって，圧縮強度を決定している繊維揺らぎを特定した．また，繊維初期不整角のばらつきが圧縮強度に与える影響を評価した．以上により，一方向CFRPの繊維揺らぎを抑制した場合の圧縮強度の向上率を定量的に評価することができるようになった．