Development of Smart Pultruded Composite Materials with Embedded Fiber Bragg Gratings for In-Situ Strain Monitoring

摘要

The major benefits of using composite materials as civil engineering structures arehigh strength, lightweight, high corrosion resistance, high formability and tailoring.Adding functionalities into composite materials, resulting in so-called smart structures,is a promising alternative to conventional methods for structural health monitoring.A large smart composite platform (20m x 3.5m) was built in september 2012(DECID2 project). All sub-structures of the platform are made by pultrusion which isa manufacturing process for producing reinforced composite structural shapes ofcontinuous lengths with constant cross-sections. Two composite girders (I-beam crosssection) are used to support small composite beams on which precast composite deckhave been assembled. The monitoring of this structure is based on Fiber BraggGratings (FBG) which are used as strain and temperature sensors. This kind of sensorexhibits numerous advantages such as small size, relative lightness, an immunity toelectromagnetic interference, geometrical flexibility and so on. In our project, FBGsensors are embedded in composite girders during fabrication. The embedment ofoptical fiber sensors in pultruded composite materials was one of the key- technicalchallenges. The ingress and egress of optical fiber from a composite component madeby pultrusion are real issues which are difficult to solve. Indeed, ingress and egress ofoptical fiber must be enough robust for the successful, cost-effective development ofembedded sensor technology. In our project, we have developed and tested aminiaturized connector which can be embedded in composite component duringpultrusion process. This connector can withstand the harsh conditions (hightemperature and shear stresses) of the pultrusion process.We will also discuss the mechanical performance of optical fiber sensors whileembedded in pultruded materials. Quasi-static and fatigue mechanical tests have beenperformed on composite specimens. The results show that embedded FBG sensorscould monitor strain with a good precision although a slightly decrease of fatigueperformance of smart composite specimens was noticed.