Definition
The property of a material that contains small voids or pores, allowing gas or liquid to pass through it or be absorbed into it. In aircraft maintenance, porosity often refers to small holes or cavities in welds, castings, or composite layups that weaken the part and can allow leaks.
Plain English
How full of tiny holes a material is. A porous material has lots of small gaps inside it; a non-porous one is solid all the way through.
Context Anchor
Seen in aircraft maintenance when inspecting parts, welds, castings, filters, coatings, and repaired surfaces.
Derivation
From the Latin porus, meaning 'pore' or 'small opening,' plus the suffix -ity, meaning 'the state of.' So porosity literally means 'the state of having pores.' That helps because the word always points back to small openings in the material, not the material's overall strength or density.
Why Pilots Care
Porosity weakens structural components and can cause cracks or failures in flight-critical parts.
Analogy
A sponge has high porosity because it contains many small open spaces. A solid metal block has very low porosity because it has little empty space inside.
Intuition Check
Porosity does not always mean large, visible holes. In maintenance, the concern is often tiny internal spaces or pinholes that may only show up during inspection or testing.
Example Sentence 1
The technician rejected the weld after the inspection revealed porosity along the bead.
Example Sentence 2
Excessive porosity in the casting reduced the part's fatigue strength.