Investigation on failure mechanisms of composite structures subjected to 3D state of stresses

2012 ◽  
pp. 33-42
Author(s):  
D. Leveque ◽  
F. Laurin ◽  
A. Mavel ◽  
N. Carrere ◽  
J.-M. Laborie ◽  
...  
Keyword(s):  
Composite Structures ◽  
Failure Mechanisms

Identifying failure mechanisms of composite structures under compressive load

1998 ◽  
Vol 35 (12) ◽  
pp. 1137-1161 ◽  
Author(s):  
L.C. Wu ◽  
C.Y. Lo ◽  
T. Nakamura ◽  
A. Kushner
Keyword(s):  
Composite Structures ◽  
Failure Mechanisms ◽  
Compressive Load

scholarly journals Reconstruction of Barely Visible Impact Damage in Composite Structures Based on Non-Destructive Evaluation Results

Sensors ◽  
2019 ◽  
Vol 19 (21) ◽  
pp. 4629 ◽  
Author(s):  
Wronkowicz-Katunin ◽  
Katunin ◽  
Dragan
Keyword(s):  
Composite Structures ◽  
Impact Damage ◽  
Failure Mechanisms ◽  
Structural Safety ◽  
Non Destructive Testing ◽  
Destructive Testing ◽  
X Ray ◽  
Computed Tomographic ◽  
X Ray Computed ◽  
Non Destructive

The occurrence of barely visible impact damage (BVID) in aircraft composite components and structures being in operation is a serious problem, which threatens structural safety of an aircraft, and should be timely detected and, if necessary, repaired according to the obligatory regulations of currently applied maintenance methodologies. Due to difficulties with a proper detection of such a type of damage even with non-destructive testing (NDT) methods as well as manual evaluation of the testing results, supporting algorithms for post-processing of these results seem to be of a high interest for aircraft maintenance community. In the following study, the authors proposed new approaches for BVID reconstruction based on results of ultrasonic and X-ray computed tomographic testing using authored advanced image processing algorithms. The studies were performed on real composite structures taking into consideration failure mechanisms occurring during impact damaging. The developed algorithms allow extracting relevant diagnostic information both from ultrasonic B-and C-Scans as well as from tomographic 3D arrays used for the validation of ultrasonic reconstructed damage locations, which allows for a significant improvement of the detectability of BVID in tested structures. The developed approach can be especially useful for NDT operators evaluating the results of structural NDT inspections.

scholarly journals The Working Principles of a Multifunctional Bondline with Disbond Stopping and Health Monitoring Features for Composite Structures

2021 ◽  
Vol 5 (2) ◽  
pp. 51
Author(s):  
Julian Steinmetz ◽  
Thomas Löbel ◽  
Oliver Völkerink ◽  
Christian Hühne ◽  
Michael Sinapius ◽  
...  
Keyword(s):  
Health Monitoring ◽  
Composite Structures ◽  
Failure Mechanisms ◽  
Design Feature ◽  
Crack Arrest ◽  
Bolted Joints ◽  
Light Weight ◽  
Health Monitoring System ◽  
The Status ◽  
Safety Features

In comparison to bolted joints, structural bonds are the desirable joining method for light-weight composite structures. To achieve a broad implementation of this technology in safety critical structures, the issues of structural bonds due to their complex and often unpredictable failure mechanisms have to be overcome. The proposed multifunctional bondline approach aims at solving this by adding two safety mechanisms to structural bondlines. These are a design feature for limiting damages to a certain size and a structural health monitoring system for damage detection. The key question is whether or not the implementation of both safety features without deteriorating the strength in comparison to a healthy conventional bondline is possible. In previous studies on the hybrid bondline, a design feature for damage limitations in bondlines by means of disbond stopping features was already developed. Thus, the approach to evolve the hybrid bondline to a multifunctional one is followed. A thorough analysis of the shear stress and tensile strain distribution within the hybrid bondline demonstrates the feasibility to access the status of the bondline by monitoring either of these quantities. Moreover, the results indicate that it is sufficient to place sensors within the disbond stopping feature only and not throughout the entire bondline. Based on these findings, the three main working principles of the multifunctional are stated. Finally, two initial concepts for a novel multifunctional disbond arrest feature are derived for testing the fundamental hypothesis that the integration of micro sensors into the disbond stopping feature only enables the crack arrest and the health monitoring functions, while reaching the mechanical strength of a conventional healthy epoxy bondline. This work therefore provides the fundamentals for future investigations in the scope of the multifunctional bondline.

scholarly journals Phase-Field Modeling of Damage and Fracture in Laminated Unidirectional Fiber Reinforced Polymers

2021 ◽  
Vol 9 (2) ◽  
pp. 110-116
Author(s):  
Aamir Dean ◽  
Pavan Kumar ◽  
Ammar Babiker ◽  
Martin Brod ◽  
Salih Elhadi Mohamed Ahmed ◽  
...  
Keyword(s):  
Phase Field ◽  
Composite Structures ◽  
Failure Mechanisms ◽  
Matrix Cracking ◽  
Fiber Reinforced Polymers ◽  
Failure Behavior ◽  
Fiber Reinforced ◽  
Reinforced Polymers ◽  
Unidirectional Fiber ◽  
Damage And Fracture

The damage and fracture behavior of Fiber Reinforced Polymers (FRPs) is quite complex and is different than the failure behavior of the traditionally employed metals. There are various types of failure mechanisms that can develop during the service life of composite structures. Each of these mechanisms can initiate and propagate independently. However, in practice, they act synergistically and appear simultaneously. The difficulties that engineers face to understand and predict how these different failure mechanisms result in a structural failure enforce them to use high design safety factors and also increases the number of certification tests needed. Considering that the experimental investigations of composites can be limited, very expensive, and time-consuming, in this contribution the newly developed multi Phase-Field (PF) fracture model [1] is employed to numerically study the failure in different Unidirectional Fiber Reinforced Polymers (UFRPs) laminates, namely, fracture in single-edge notched laminated specimens, matrix cracking in cross-ply laminates, and delamination migration in multi-layered UFRPs. The formulation of the PF model incorporates two independent PF variables and length scales to differentiate between fiber and inter-fiber (matrix-dominated) failure mechanisms. The physically motivated failure criterion of Puck is integrated into the model to control the activation and evolution of the PF parameters. The corresponding governing equations in terms of variational formulation is implemented into the Finite Element (FE) code ABAQUS utilizing the user-defined subroutines UMAT and UEL.  

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