Abstract

The accuracy of fracture toughness is pivotal for the safety of composite and nanocomposite systems, with various techniques developed to measure fracture energy across different modes. Apparatus compliance issues arising from geometric non-linearities remain a significant concern and warrant further investigation. In the late 1980s, NASA introduced the Mixed-Mode Bending (MMB) apparatus to assess mixed-mode I-II strain energy release rates. Very recently, Arizona State University (ASU) researchers refined MMB into the Reinforced Mixed-Mode Bending (RMMB) apparatus for improved accuracy. This advancement involves redesigning MMB components to enhance stiffness and interlaminar fracture toughness measurements, crucial for predicting crack initiation and propagation accurately. Over the past three decades, laminated composite and nanocomposite materials have seen increased demand in aerospace, nuclear, and space technology due to their high strength-to-weight and stiffness-to-weight ratios. However, delamination remains a persistent challenge despite manufacturing improvements. Carbon nanotube (CNT) membranes have been employed to enhance mechanical properties and mitigate delamination, prompting extensive research into their integration with composites. The interlaminar fracture toughness of laminated composites reinforced with CNT membranes using the MMB & RMMB fixtures will be examined. Finite element analysis (FEA) will aid in understanding fixture compliance, energy release rate initiation and propagation, and fracture toughness envelope functions. Fracture tests comparing MMB and RMMB methods will be conducted, with load-displacement curves analyzed across various mixed-mode ratios.

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