What is the primary method by which acoustic emission testing identifies defects in composite materials?

Acoustic emission testing is an advanced technique that detects and identifies defects in composite materials by capturing and analyzing the sound waves emitted from these materials as they undergo stress or strain. When a composite structure experiences degradation, such as cracking or delaminating, it generates stress waves that travel through the material. These sound waves, or "noise," are recorded using sensitive microphones or transducers.

The technique relies on the principle that different types of defects produce characteristic sound patterns, and by analyzing these patterns, testers can ascertain the nature and severity of the damage without needing to physically access or disturb the structure. This method provides real-time monitoring and can detect defects that may not be visible through traditional visual inspections or manifested as temperature changes.

Other options like measuring temperature variations or conducting visual inspections are not inherently linked to the dynamic monitoring of structural integrity in the way acoustic emission testing is. Analyzing tensile strength also doesn't provide insights into the ongoing deterioration processes within the composite material, which is critical for understanding and maintaining its safety and functionality. Hence, the primary method of identifying defects through acoustic emission testing is indeed centered around detecting the 'noise' produced by deterioration.