ERI: Mechanistic Quantification of Defect-Mediated Crack Initiation and Very High Cycle Fatigue Response in Additive Manufactured Aerospace-Grade Aluminum Nanocomposites

The rapid advancement of additive manufacturing has enabled the design of high-strength, lightweight metallic components for fatigue-critical applications such as aircraft engines, high-speed trains, and space systems. However, these components are increasingly expected to perform reliably under extremely long service lives, often exceeding 10 million loading cycles. This regime, known as very high cycle fatigue, remains a largely unexplored frontier, particularly for advanced additively manufactured, high-strength, lightweight materials including metal matrix composites. Addressing this knowledge gap is essential to ensure the safety and durability of next-generation structural components in sectors that underpin national security, technological leadership, and economic prosperity. This Engineering Research Initiation (ERI) award supports research that seeks to advance the scientific understanding of fatigue behavior in a novel additively manufactured aluminum matrix nanocomposite under loading conditions beyond 10 million cycles. This award is expected to improve fatigue resilience of additively manufactured parts and support manufacturing workforce development. This award is expected to establish a science-based, comprehensive experimental and analytical framework to evaluate the extended fatigue performance (10 million to 10 billion cycles) of recently developed Al-Cu nanocomposites, reinforced with Ti-based nanoparticles, produced by laser-based additive manufacturing processes. Two classes of specimens, “defect-free” and “artificially defective”, will be fabricated to isolate the effects of volumetric defects and microstructural features on fatigue life. High-frequency (20 kHz) ultrasonic fatigue testing will be combined with advanced microscopy and post-mortem imaging techniques seeking to uncover the micro-mechanisms of internal crack initiation (the controlling stage of fatigue failure in the very high cycle fatigue regime). Research tasks look to quantify the influence of additive manufacturing process variables, as well as post-processing treatments such as heat treatment and hot isostatic pressing, on fatigue performance. The findings seek to inform predictive models of cyclic damage in additively manufactured materials subjected to ultralong fatigue life conditions. Results from this award look to advance the state of knowledge in very high cycle fatigue regime and provide practical insights for the design and certification of durable, defect-tolerant components. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.