Influence of width on the tensile properties of ±45° fiber-reinforced composites using DIC and AE

• Combined DIC and AE for synchronous monitoring of ±45° CFRP tensile tests. • Specimen width shifts failure from matrix cracking to fiber-dominated fracture. • PCA and FCM clustering identified matrix, interface, and fiber damage modes. • Wider specimens show uniform strain and “diamond” shear bands predicting failure. • Findings support ASTM/ISO standard refinement and structural design guidance. This study investigates the width-dependent tensile behavior and damage mechanisms of ±45° carbon fiber–reinforced polymer (CFRP) laminates through an integrated Digital Image Correlation (DIC) and Acoustic Emission (AE) monitoring framework. Specimens of three widths (25 mm, 45 mm, and 100 mm) were subjected to quasi-static tensile loading while synchronously recording full-field strain evolution and internal damage events. DIC results reveal a clear transition in strain-field morphology with increasing width, from narrow banded shear localization to broader and more uniform “diamond-shaped” deformation patterns. AE monitoring captures corresponding changes in internal damage progression. After screening AE events above 40 dB and within the 100–600 kHz bandwidth, multi-parametric AE features were reduced using factor analysis/PCA, which revealed distinct clustering distributions associated with different specimen widths. Narrow specimens exhibited feature concentrations linked to matrix-dominated microcracking, medium-width specimens showed mixed matrix–interface interactions, and wide specimens exhibited high-energy signatures corresponding to fiber-dominated fracture. These dimensionality-reduction results directly demonstrate how specimen width regulates the underlying damage modes and AE response characteristics. Overall, the combined AE–DIC analysis provides a multi-scale understanding of deformation–damage coupling in ±45° CFRP laminates and offers quantitative evidence useful for structural design optimization and refinement of relevant ASTM/ISO shear testing standards.