Self-confining-pressure structures double the compressive strength of metamaterials by applying lessons from nature and architecture

• SCPS achieving a twofold increase in compressive strength is proposed. • First observation and investigation of SCPS-induced dislocation multiplication. • Tailoring mechanical properties using architectural motifs is presented. Metallic materials with high strength-to-weight ratios, or specific strengths, have been sought after for centuries, from aircraft and automobiles to electronic devices and biomedical implants. Inspired by tube-in-tube structures in nature and architecture, we fabricate metallic metamaterials with self-confining-pressure structures (SCPS), achieving exceptional compressive yield strength up to 1272 MPa (a specific strength of 379.7 kN∙m/kg) in AlSi7Mg-Ti6Al4V (Al-Ti) metamaterials. Such metamaterials—exceeding that of its constituents, while maintaining an asymmetrical tensile yield strength up to 696 MPa. This remarkable strength amplification originates from the induced triaxial stress state within the SCPS architecture and confining-pressure-induced dislocation multiplications. We propose a mechanical model that quantitatively captures the strengthening effect of SCPS. The design strategy of SCPS significantly enhances the compressive strength ceilings of existing structural materials without sacrificing their tensile strength and ductility, enabling anisotropic mechanical performance for demanding aerospace, automotive, and a wide range of engineering applications.