Application of Distributed Fiber Optic Strain Sensors for Local Indentation/Impact Damage Detection in Foam Core Composite Sandwich Structures

摘要

Local indentation or low-velocity impact of foam core sandwich structures can leave only barely visible damage in the face sheet while the core can be notably damaged leading to degraded strength of the structure. In the present study a high spatial resolution Rayleigh scattering based distributed fiber optic strain sensors were applied to foam core sandwich structures to detect the barely visible indentation and impact induced damages. Monitoring ability of the system was studied experimentally by conducting indentation and low-velocity impact tests with sandwich beam and panel structures. Strain distribution in the sandwich structures was monitored using the embedded optical fiber sensors. The measurement results were verified against predictions by finite element analysis and a simple way to estimate the damaged core area was defined. Location and size of damage in the structures was estimated with high precision from the strain distribution data. The used system was seen to provide a fast and easy way to monitor and assess barely visible damage in sandwich structures.