4D printing for crack trapping and adaptive damage-tolerant structures

Purpose This paper reviews damage tolerance in 4D-printed mechanical structures, focusing on how material selection, design strategies, and the 4D printing process influence resilience under stress. It highlights the role of smart materials, metamaterials and adaptive behaviors—such as self-sensing and shape change—in detecting and mitigating damage. Design/methodology/approach This review adopts a systematic approach to analyze recent advancements in damage tolerance within 4D-printed structures. It examines peer-reviewed literature across materials science, mechanical engineering and additive manufacturing, with a focus on self-sensing, adaptive mechanisms and fatigue behavior. The methodology includes comparative analysis of material systems, printing strategies and structural designs that enhance durability under cyclic loading. Special emphasis is placed on metamaterials and time-dependent functionalities enabled by 4D printing. By evaluating experimental and computational studies, the review identifies key design principles and fabrication methods that contribute to improved damage mitigation and long-term structural performance. Findings The review shows that 4D-printed structures can better handle damage when smart materials, especially metamaterials, and designs that change over time are used, allowing them to adapt to mechanical stress. Key findings highlight the effectiveness of self-sensing and shape-morphing capabilities in detecting and mitigating damage, particularly under cyclic loading and fatigue conditions. Layer-by-layer control and stimulus-responsive behaviors contribute to improved crack deflection, energy dissipation and structural recovery. Originality/value This review offers a unique synthesis of current research on damage-tolerant design in 4D-printed structures, bridging insights from materials science, additive manufacturing and structural mechanics. Its originality lies in framing damage tolerance as a multi-functional outcome enabled by 4D printing’s intrinsic capabilities—such as self-adaptivity, shape transformation and time-dependent material behavior.