In Situ Micro‐ CT Study of the Effect of Fiber Content on Tensile Damage Evolution in Short Carbon Fiber‐Reinforced Polypropylene Composites

ABSTRACT

Short carbon fiber‐reinforced polypropylene (SCF/PP) composites with a fixed initial fiber length of 0.5 mm are investigated to determine how fiber content changes tensile damage pathways. Nominal SCF contents of 5, 15, and 30 wt% correspond to thermogravimetric analysis (TGA) values of 4.6 ± 0.6, 14.2 ± 1.2, and 28.3 ± 2.2 wt%, respectively. The elastic modulus increases from 2.8 to 5.3 GPa, whereas tensile strength rises from 42 to 53 MPa and then decreases to 47 MPa; elongation at break decreases from 13.1% to 4.8%. Synchrotron in situ micro‐computed tomography (micro‐CT), tensile testing, and scanning electron microscopy (SEM) reveal a transition from matrix‐dominated ductile deformation and progressive debonding to distributed quasi‐brittle damage with crack deflection and bridging, and finally to agglomeration‐controlled through‐crack formation. Within the tested fixed‐fiber‐length and fixed‐compatibilizer system, 15 wt% provides the best balance of strength, stiffness, and ductility.