Compressive Strength

Theory

Compressive strength (σ_c) is measured by loading a short specimen in axial compression until failure. For ductile materials, failure is by plastic yielding (barrelling); for brittle materials, by shear-plane fracture at ~45°. For many metals σ_c ≈ σ_UTS; for brittle ceramics σ_c >> σ_UTS (concrete compressive strength is 10× its tensile strength). Slender specimens fail by buckling before material fracture.

Application

Compressive loads arise in columns, chair legs, press-fit bosses, and stacked components. FDM performs relatively well in compression: layers press together rather than separating. For porous infill, compressive stiffness and strength scale with infill percentage. Sandwich structures (face-sheet + infill core) maximise compressive stiffness per unit mass.

Common mistakes

Buckling failure (Euler buckling: F_cr = π²EI/L²) occurs at loads far below material compressive strength for slender FDM parts. Friction at end platens during testing artificially raises measured compressive strength. Infill pattern strongly affects compressive performance: gyroid and honeycomb infills carry compressive loads more efficiently than rectilinear.

Related terms: Tensile Strength, Stress, Stiffness, Bending Moment