Correlating full-field strain localization and microstructural failure mechanisms in 2D textile CF/PPS composites

This study presents the experimental characterization of a polyphenylene sulfide (PPS) matrix reinforced with a 2D textile carbon-fiber architecture, using macroscale mechanical testing combined with microscale fractographic analysis. The purpose of this work is to investigate the mechanical behavior and damage mechanisms of CF/PPS composite laminates under tensile, compressive, and shear loading using full-field strain measurements and microstructural observations. Quasi-static tensile (ASTM D3039), compression (ASTM D6641), and shear (ASTM D7078) tests were performed in the warp and fill directions, with Digital Image Correlation (DIC) used for full-field strain measurements. Microstructural analyses of fractured specimens were carried out using optical microscopy, stereoscopy, and scanning electron microscopy (SEM). Tensile tests revealed linear-elastic behavior up to brittle failure, with elastic moduli of approximately 54 GPa and tensile strengths of approximately 733-714 MPa in the warp and fill directions. Compression tests showed nearly linear behavior with failure dominated by fiber microbuckling and progressive delamination, with compressive strengths between 523 and 545 MPa. Shear tests exhibited nonlinear behavior due to fiber reorientation and locking effects, with shear strengths of 66–67 MPa. DIC measurements enabled the identification of strain localization and damage initiation sites under all loading conditions, showing strong correlation with microstructural features such as fiber microbuckling, matrix plastic deformation, and interlaminar damage. The combined use of Digital Image Correlation and microstructural analysis provided a comprehensive understanding of the mechanical response and failure mechanisms of CF/PPS laminates under different loading conditions, highlighting the strong relationship between full-field strain evolution and the underlying microstructural damage processes.