By embedding an optical fibre in a composite structure, the possibility is created to measure multi-axial strains. This possibility comes from the intrinsic multi-axial strain sensitivity of an optical fibre. Different types of optical fibre sensors can be used to obtain this feature of which the regular DTG®s are still the most simple to use since no extra orientation step of the optical fibre is needed.  The spectrum of such DTG splits into two peaks which can be used to monitor more than one direction in the composite part. An example of a DTG® embedded in a cross ply and its spectrum when coated or non-coated is given below.

If higher sensitivities is needed one can go use more specialized optical fibres, the so-called birefringence fibres. An example of a bow-tie fibre and its spectrum in loaded and unloaded condition is given below. The spectrum of the bow-tie and other PM-FBGs is already split from the beginning of the embedding procedure. As such it is really easy to observe any change in the spectrum concerning peak separation shifts.

In the Self Sensing Composite-project (IWT SBO-project) in which Com&Sens is member of the industrial users consortium, a Micro-structured optical firbe is being developed with unprecedented sensitivities for multi-axial strain monitoring. The idea is to position the holes created in such fibres in the most favorable way to increase the sensitivity. An example of such a fibre is given below:

Contact us for more information about this different senor types and their embedding procedure .