Damage detection of laminated composite structures using inverse finite element method

In recent years, structural health monitoring (SHM) has been revolutionized with the advent of an inverse method based on the minimization of a weighted least squares functional, known as inverse finite element method (iFEM). This approach is suitable for detection of damage, thanks to its ability in accurate full-field reconstruction of the displacement field over the problem domain. This study focuses on the application of iFEM for shape sensing and damage detection in various case studies, using numerically generated in-situ strain data via high fidelity forward finite element modeling (FEM). The study is conducted utilizing quadrilateral inverse-plane, and quadrilateral inverse-shell elements (iQS4). By utilizing the field variable achieved via the iFEM, equivalent von Mises strains are computed, after that, through definition of a damage index, the health of the structure is evaluated in terms of the presence of damage as well as its extent. Additionally, a new strategy is introduced for detection of the through-the-thickness damage in laminated composite materials by incorporating refined zigzag theory (RZT) in the iFEM algorithm. As a result of these analyses, the inverse algorithm shows its efficiency in detecting flawed regions over the problem domain and through the thickness of layered materials, both in terms of the location of the damage as well as its morphology

A novel delamination damage detection strategy based on inverse finite element method for structural health monitoring of composite structures

In recent years, structural health monitoring (SHM) has been revolutionized with the advent of the inverse finite element method (iFEM), which is a superior sensing technology based on the minimization of a weighted least squares error functional between experimental and numerical strain measures. This approach is suitable for damage detection thanks to its highly accurate and full-field displacement reconstruction capability within the physical domain of the structure. This study focuses on the development of a novel damage detection strategy for identifying internal/external defect types in composites, e.g., delamination, surface debonding, etc., by utilizing iFEM. The core formulation is derived by employing the kinematic relations of the refined zigzag theory (RZT) within the iFEM framework. By utilizing the field variables achieved via the iFEM-RZT, equivalent von Mises strains are computed for individual plies. After that, through the definition of various damage indices, the health of the structure is evaluated in terms of the presence of damage as well as its extent and through-the-thickness position and in-plane size of the damage in laminated composite materials. Various case studies with different damage scenarios are simulated for the assessment of iFEM-RZT capability in terms of shape-sensing and SHM. As a result, the inverse algorithm shows its remarkable efficiency and accuracy in detecting flawed regions over the problem domain and through the thickness of layered materials, both in terms of the location of the damage as well as its morphology