Experimental and Numerical Study on Compressive Performance of Composite Laminates With In‐Plane Fiber Waviness Induced by Reverse Forming

ABSTRACT Fiber waviness is a common manufacturing defect in carbon fiber reinforced polymer (CFRP) composites used in aerospace applications, and can markedly degrade the load‐carrying capacity of laminates, particularly under compressive loading. Focusing on the in‐plane fiber waviness induced during hot‐press forming and hot diaphragm forming of composite stringer structures, this study systematically investigates its effects on the compressive performance of composite laminates. A reverse forming method is employed to introduce representative in‐plane fiber waviness with controllable geometric characteristics, enabling the fabrication of laminates with different waviness configurations. Based on microstructural observations, the waviness morphology is quantitatively characterized, and a sine‐based double waviness band geometric model is proposed to describe the alternating distribution of waviness regions. Compressive experiments combined with finite element simulations are conducted to examine the effects of in‐plane fiber waviness on compressive response and failure modes. The results show that the proposed model captures the actual waviness morphology well, with the compressive strength prediction error within 9%. Compared with defect‐free laminates, waviness reduces compressive strength and overall stiffness, and increasing waviness severity shifts failure from localized instability to transverse shear‐dominated failure.