Dynamic characteristics of CFRP with different weaving types under hygrothermal conditions

Abstract With the expanding use of woven composites in critical load-bearing applications under harsh environmental conditions, it is essential to evaluate how hygrothermal exposure affects their performance. This study aims to systematically analyze the hygrothermal effects on the dynamic characteristics of carbon fiber reinforced polymer (CFRP) composites with different weaving types: plain, satin, and twill. Accelerated hygrothermal tests were conducted by immersing specimens in water at 70 °C for 48 days until moisture saturation. The experimental methodology integrated microstructural analysis via scanning electron microscopy (SEM), static mechanical testing, and experimental modal analysis (EMA). Additionally, a coupled hygrothermal finite element model incorporating the Tsai hygrothermal aging model was developed to predict the hygrothermal changes. SEM observations revealed substantial microstructural deterioration, including matrix pulverization, surface cracking, and increased porosity, with porosity growth rates quantified at 315 % for plain, 72.7 % for twill, and 213 % for satin weaves. The static mechanical properties of CFRPs were significantly degraded, with compressive properties being the most sensitive – twill weaves exhibited the most pronounced reduction in compressive modulus with a 40.12 % decrease, tensile and interlaminar shear strength (ILSS) properties showed relatively moderate degradation across all weaving types. Experimentally, the first five natural frequencies declined across all weaving types, with the most pronounced reduction in the fundamental frequency 1.07 % for plain, 2.08 % for twill, and 1.73 % for satin weaves. Dynamic stiffness degradation was measured at 15.7 % for plain, 10.93 % for twill, and 7.83 % for satin weaves. In contrast, damping ratios consistently increased for all specimens. The finite element simulation showed good agreement with experimental modal frequencies for low-order modes with an average error of less than 10 %, though discrepancies in higher-order modes indicated limitations in capturing microstructure-dependent hygrothermal variations. Owing to its longer float length, the satin weave exhibited the least degradation in compressive strength and dynamic stiffness, along with enhanced damping capacity resulting from high-density mechanical interlocking of matrix microparticles. Therefore, the satin weave is recommended for engineering applications in hygrothermal environments to better maintain structural dynamic stability.