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The effect of embedded optical fibers on the static and fatigue interlaminar shear strength of a glass reinforced polyester laminate is evaluated. Seventy identical specimens with and without embedded optical fibers were tested reaching more than 500,000 cycles in some cases; It was found that the optical fiber does nothave a negative influence on the laminate, neither static nor in fatigue. These tests were included into a projectto develop smart wind turbine blades. 1. INTRODUCTION This work is included into a larger project attempting to develop smart wind turbine blades (WTB). WTBs are a kind of severely stressed, hardly inspectable structures, so they would greatly benefit from a permanent damage monitoring system.Blade failure use to be really catastrophic, flying away part of the blade, and use to happen by fatiguegrowth of undetected damages produced by overloading. Design need to be conservative; if feasibility of theblade is increased, costs of the whole system could be cut significantly.The proposed system would make use of white light interferometry, with the aim of measuring the lossof stiffness that usually precedes to the blade failure. White light interferometry has many advantages for thisapplication: it is a cheap procedure, because only standard single mode optical fibre is needed; sensing regionis distributed along the fiber length; contrary to intensity based sensors, the signal does not suffer from driftingwith time or aging of the fiber. The procedure has been suggested for long term monitoring of civil structures1.Our scheme (Fig. 1) is essentially the same as those proposed, a Michelson interferometer, but differsin two concepts: First, we can control the external load of the structure during the test; by rotating the blade,the sign of the load is changed. Second, we are no interested into absolute measurement of displacement, but in |
