Monitoring the Damage State of Fiber Reinforced Composites Using an FBG Network for Failure Prediction

Abstract

A structural health monitoring (SHM) study of biaxial glass fibre-reinforced epoxy matrix composites under a constant, high strain uniaxial fatigue loading is performed using fibre Bragg grating (FBG) optical sensors embedded in composites at various locations to monitor the evolution of local strains, thereby understanding the damage mechanisms. Concurrently, the temperature changes of the samples during the fatigue test have also been monitored at the same locations. Close to fracture, significant variations in local temperatures and strains are observed, and it is shown that the variations in temperature and strain can be used to predict imminent fracture. It is noted that the latter information cannot be obtained using external strain gages, which underlines the importance of the tracking of local strains internally.

A Comparative and Review Study on Shape and Stress Sensing of Flat/Curved Shell Geometries Using C0-Continuous Family of iFEM Elements

“…The root-mean-square difference (RMSD) between iFEM and FEM results can be computed as All the benchmark cases were assessed again by the standard deviation measurement principle to further compare the accuracy and performance of iMIN3, iQS4, and iCS8 elements in terms of shape and stress sensing. The root-mean-square difference (RMSD) between iFEM and FEM results can be computed as 11) where the N n term represents the total number of nodes in the global iFEM discretization and the δ parameter corresponds to either total displacement, U T or von Mises stress, σ vm . As is inferred from Equation ( 11), the stability of the results obtained using different iFEM elements does not depend on a single node having the maximum displacement/stress value, since all nodes contribute to the increasing stability of the results in the standard deviation calculation.…”

“…The SHM of simple and complex structural topologies (e.g., shell models with surface cracks [ 6 , 7 ]) made of isotropic materials (e.g., steel/aluminum structures [ 2 , 3 , 8 ]) or orthotropic materials (e.g., multilayered composite and sandwich structures [ 9 , 10 ]) are studied under static and dynamic loading conditions. Particularly, damage, delamination, and fatigue in laminated composite and foam-core sandwich structures were identified using embedded fiber optic sensors [ 11 , 12 , 13 ].…”

Defects detection from time series of cutting force in composite milling process by recurrence analysis

“…10 Evaluation of the surface condition of polymer composites can be carried out by destructive and nondestructive methods. Destructive tests 11,12 include strength tests, thermaldegradation processes, thermoxidation and photooxidation. An examination of samples under load [13][14][15] reveals the place of rupture, which always occurs at the site of the defect.…”

“…In this article, the recurrence time of the first type (T1), when the point belongs to the recurrence vector and the recurrence time of the second type (T2), when the point does not belong to the recurrence vector, are shown. These quantifications are represented by formulas (11) and (12)…”

Crack Propagation Calculations for Optical Fibers under Static Bending and Tensile Loads Using Continuum Damage Mechanics

“…On account of high capacity and low transmission loss, optical fibers are mostly used in long-haul communication systems. Additionally, they are also widely applied in sensors [ 1 , 2 , 3 ], considering their excellent flexibility and compact size. Owing to the severe environmental conditions, the optical fibers in sensors face some challenges in terms of the reliable functional guarantee and long lifetime requirement.…”