Mechanics of Composite, Hybrid, and Multifunctional Materials, Fracture, Fatigue, Failure and Damage Evolution, Volume 3 of the Proceedings of the 2021 SEM Annual Conference & Exposition on Experimental and Applied Mechanics, the third volume of four from the Conference, brings together contributions to this important area of research and engineering.  The collection presents early findings and case studies on a wide range of areas, including:Recycled Constituent CompositesDamage DetectionAdvanced Imaging of CompositesMultifunctional MaterialsComposite InterfacesTunable CompositesNovel Experimental MethodsExtreme EnvironmentsInterfacial FractureIntegration of Models & ExperimentsMechanics of Energy & Energetic MaterialsIntegration of Models & ExperimentsIn Situ Techniques for Fatigue & FractureMicroscale & Microstructural Effects on Mechanical Behavior