Numerical and experimental investigation of the interface properties and failure strength of CFRP T-Stiffeners subjected to pull-off load

• Published in: Materials & design Vol. 185; p. 108231
• Main Authors: Ma, Xueshi, Bian, Kan, Liu, Hongguang, Wang, Yi, Xiong, Ke
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 05-01-2020; Elsevier
• Subjects: CFRP T-stiffener; Failure strength; Filler cracking; Interface debonding; Filler cracking; Interface debonding; CFRP T-stiffener; Failure strength
• ISSN: 0264-1275; 1873-4197
• DOI: 10.1016/j.matdes.2019.108231

This paper focuses on interface properties between the composite laminae, and the failure strength of carbon fiber reinforced polymer (CFRP) T-stiffeners in a pull-off test. Interfacial fracture toughness was studied and optimized based on the theoretical method and experimental observations in the scanning electron microscope (SEM) view, due to the insertion of fibers or fiber tows into interface adhesive layers created in the manufacturing process. Numerical load-displacement curves associated with different interfacial fracture toughness were calculated and compared with experimental load-displacement curves. It was found that the load-displacement curve calculated by the optimized interfacial fracture toughness was in better agreement with experimental records. Additionally, the filler cracking and interface debonding was numerically predicted using the extended finite element method (XFEM) combined with cohesive zone model (CZM) and experimentally recorded using a high-speed camera. The digital image correlation (DIC) technique was further used to capture deformations and strain distributions in the radius region. Strain distributions obtained from the combined numerical calculation and experimental DIC could help in better understanding the failure mechanisms of CFRP T-stiffeners.
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•We proposed a modification of the interfacial fracture toughness induced by the fiber insertion.•It was simulated that noodle cracking induced interface debonding was responsible for the final failure.•Monitoring by digital image correlation indicated high load in flange direction led to the noodle crack.