Study on the transverse strength and modulus testing of large tow carbon fiber monofilaments

Large-towel carbon fiber (LCF) offers excellent cost-effectiveness and higher processing efficiency, and its development has been rapid. Understanding the engineering constants of large-towel carbon fiber monofilaments is crucial for designers. This paper proposes a method using an angled tensile test deviating from the axial direction to determine the engineering properties of LCF single filaments, including the axial tensile modulus E3 of 218 GPa, the transverse tensile modulus E1 of 67 GPa, and the shear modulus G13 of 42 GPa. Using the Cai-Wu failure criterion, the longitudinal strength X, transverse strength Y, and shear strength S of the carbon fiber filaments were determined to be 4063 MPa, 812 MPa, and 890 MPa, respectively. The ultimate strength values in all directions for the large-towel carbon fiber were also obtained. By processing the experimental data and applying the Weibull distribution, the corresponding parameter values were obtained, and the final parameters were solved using these values. Electron microscope testing was conducted on the large-towel carbon fiber to observe the fracture morphology of the single filaments. The results indicated that the structure of the large-towel carbon fiber, as observed macroscopically, consists of a shell-and-core structure.