Deformation measurement within adhesive bonds of aluminium and CFRP using advanced fibre optic sensors

Abstract

Monitoring the deformation within an adhesive joint during the curing cycle provides valuable information regarding the build-up of thermal strain and stress. Distributed fibre optic sensors are very useful for spatial continuous measurements of deformation or temperature. Integrated into a hybrid joint, the thermal curing process of the adhesive can be monitored. This detailed insight into the joint helps to understand the deformation and thereby also the resulting stress. Analysing the deformation process establishes the foundation to adapt techniques to reduce the thermally induced deformation and thereby the resulting stress.

Adhesive Joint Integrity Monitoring Using the Full Spectral Response of Fiber Bragg Grating Sensors

“…Instead of directly looking for defects, there are relatively more economical techniques suitable for real-time monitoring of the integrity degradation of adhesive joints. These include strain/stiffness monitoring using back face strain gages [21][22][23], resistance monitoring of adhesive joints made conductive by adding carbon nanotubes [24,25] and optical fiber sensors signal surveillance [26][27][28][29][30][31][32][33][34][35][36][37][38][39][40][41][42][43]. Strain gages can only be applied to the outer surface, but they will disrupt an otherwise smooth surface and are susceptible to environmental degradation.…”

“…There are different kinds of optical fiber sensors. In adhesive joints, both the distributed sensing [29][30][31] and the discrete fiber Bragg grating (FBG) sensors have been used [8,[32][33][34][35][36][37][38][39][40][41][42][43]. The distributed sensors provide a spatially continuous strain measurement along the whole fiber and can reveal the location of any perturbation in strain caused by damages in the bond.…”

Damage Monitoring of Composite Adhesive Joint Integrity Using Conductivity and Fiber Bragg Grating

“…Instead of directly looking for defects, there are techniques suitable for real-time monitoring of the integrity degradation of adhesive joints. These include strain/stiffness monitoring using back face strain gages [ 21 , 22 , 23 ], optical fiber sensors signal surveillance [ 24 , 25 , 26 , 27 , 28 , 29 , 30 , 31 , 32 , 33 , 34 , 35 , 36 , 37 , 38 , 39 , 40 , 41 , 42 , 43 , 44 , 45 , 46 , 47 , 48 , 49 ], and resistance monitoring of conductive adhesive joints [ 50 , 51 , 52 , 53 , 54 , 55 , 56 , 57 , 58 , 59 , 60 , 61 , 62 , 63 , 64 , 65 , 66 , 67 ]. Strain gages can only be applied to the outer surface.…”

Hygrothermal Damage Monitoring of Composite Adhesive Joint Using the Full Spectral Response of Fiber Bragg Grating Sensors

“…Instead of monitoring moisture content or directly looking for defects, there are techniques suitable for real time monitoring of the integrity degradation of adhesive joints. These include strain/stiffness monitoring using back face strain gages [ 49 , 50 , 51 ], resistance monitoring of adhesive joints that were made conductive by adding carbon nanotubes [ 52 , 53 ] and optical fiber sensors signal surveillance [ 43 , 44 , 54 , 55 , 56 , 57 , 58 , 59 , 60 , 61 , 62 , 63 , 64 , 65 , 66 , 67 , 68 , 69 , 70 , 71 , 72 , 73 ]. Strain gages can only be applied to the outer surface, they will disrupt an otherwise smooth surface and are susceptible to environmental degradation.…”

“…There are different kinds of optical fiber sensors. In adhesive joints, both the distributed sensing [ 57 , 58 , 59 ] and the discrete fiber Bragg grating (FBG) sensors have been used [ 30 , 60 , 61 , 62 , 63 , 64 , 65 , 66 , 67 , 68 , 69 , 70 , 71 , 72 , 73 ]. The distributed sensors measured strain along the fiber and is equivalent to a train of strain gages with the best available spatial resolution going down to the millimeter range.…”