Failure analysis of low velocity impact on thin composite laminates: Experimental and numerical approaches (original) (raw)

Numerical and Experimental Analyses of Low Velocity Impact on Thin Composite Laminates

2011

The dynamic behavior of composite laminates is very complex because there are many concurrent phenomena during composite laminate failure under impact load. Fiber breakage, delaminations, matrix cracking, plastic deformations due to contact and large displacements are some effects which should be considered when a structure made from composite material is impacted by a foreign object. Thus, the mechanical material behavior is simulated using a phenomenological model that considers five failure modes: two for fiber-failure (FF) and three for inter-fiber-failure (IFF). In FF modes, the lamina failures under longitudinal tension or compression. In IFF modes, the lamina failures under transverse tension (Mode A), or transverse compression (Mode B or C). Each failure mode has a failure criteria and an associated degradation function that decreases the engineering material properties, turning the process of analysis iterative. The material model is implemented in a sub-routine written in Fortran (UMAT and VUMAT) and used together the finite element package Abaqus for implicit and explicit numerical solution. First, the material parameters are identified and calibrated using case studies based on 3-point bending problem. Thus, finite element analyses are performed for a set of parameters through a Matlab program that controls the parameters variability and generate the results of interest which are then evaluated. After calibration procedure, the material model is used to predict the response of thin disks under impact loads. Finally, the numerical simulations are compared to experimental results, and limitations, as well as potential of material model implemented are discussed.

Testing and modeling of damages in composite laminates subject to low velocity impact

In recent years, composite materials were used extensively in the most important industries, especially in aerospace industries and aircraft structures due to its high strength, high stiffness, resistance of corrosion, and lightweight. The problem is how to choose the perfect design for composite laminates. And study the effects of modeling of the stacking sequences of composite laminates on failure modes (delamination, matrix cracking, and fiber failure) under the test of low velocity impact. This paper has validating to the experimental results that has published. The composite used was carbon fiber /epoxy (CFRE), (UD ASTM/D6641) as three groups [A, B, C]. It had same material system. The difference was only in stacking sequences as random design. These models were simulated numerically by the commercial software implemented into the FEM/ABAQUS 6.9.1 with subroutine file (VUMAT) a user-define 3D damage model. The results had good agreement with experimental results.

Numerical and experimental analyses of low velocity impact on thin composite

2013

The dynamic behavior of composite laminates is very complex because there are many concurrent phenomena during composite laminate failure under impact load. Fiber breakage, delaminations, matrix cracking, plastic deformations due to contact and large displacements are some effects which should be considered when a structure made from composite material is impacted by a foreign object. Thus, the mechanical material behavior is simulated using a phenomenological model that considers five failure modes: two for fiber-failure (FF) and three for inter-fiber-failure (IFF). In FF modes, the lamina failures under longitudinal tension or compression. In IFF modes, the lamina failures under transverse tension (Mode A), or transverse compression (Mode B or C). Each failure mode has a failure criteria and an associated degradation function that decreases the engineering material properties, turning the process of analysis iterative. The material model is implemented in a sub-routine written in Fortran (UMAT and VUMAT) and used together the finite element package Abaqus for implicit and explicit numerical solution. First, the material parameters are identified and calibrated using case studies based on 3-point bending problem. Thus, finite element analyses are performed for a set of parameters through a Matlab program that controls the parameters variability and generate the results of interest which are then evaluated. After calibration procedure, the material model is used to predict the response of thin disks under impact loads. Finally, the numerical simulations are compared to experimental results, and limitations, as well as potential of material model implemented are discussed.

Low-velocity impact tests on carbon/epoxy composite laminates: A benchmark study

Composites Part B: Engineering, 2016

Low-velocity impacts (LVI) on composite laminates pose significant safety issues since they are able to generate extended damage within the structure, mostly delaminations and matrix cracking, while being hardly detectable in visual inspections. The role of LVI tests at the coupon level is to evaluate quantities that can be useful both in the design process, such as the delamination threshold load, and in dealing with safety issues, that is correlating the internal damage with the indentation depth. This paper aims at providing a benchmark of LVIs on quasi-isotropic carbon/epoxy laminates; 2 laminates are tested, 16 and 24 plies and a total of 8 impact energies have been selected ranging from very low energy impacts up to around 30 J. Delamination threshold loads, shape and extension of delaminations as well as post-impact 3D measurements of the impacted surface have been carried out in order to characterize the behavior of the considered material system in LVIs. The analysis of test results relevant to the lowest energies pointed out that large contact force fluctuations, typically associated to delamination onset, occurred but ultrasonic scans did not reveal any significant internal damage. Due to these unexpected results, such tests were further investigated through a detailed FE model. The results of this investigation highlights the detrimental effects of the dissipative mechanisms of the impactor. A combined numerical-experimental approach is thus proposed to evaluate the effective impact energies.

Prediction of low velocity impact damage in carbon–epoxy laminates

Composites Part A: Applied Science and Manufacturing, 2002

The paper deals with the analysis for damage in carbon/epoxy laminates subjected to low velocity impact. The study is related to application of carbon fiber composites in airframe structures. In this paper, FEM 3D analysis for modeling and predicting the damage in carbon-epoxy laminate subjected to low velocity impact were performed. The model of finite elements assuming the interlamiar shear stresses continuity between different oriented layers is presented. Two different laminates were evaluated employing VUMAT redeveloped ABAQUS. The occurrence of matrix failure and the delaminated areas were predicted by using the failure criteria based on empirical relation and other developed criteria. Comparisons with test data for a damaged carbon-epoxy laminate are provided for model verifications. A good agreement between analysis and experimental results for the mode and orientation of delaminations were obtained. This approach provides a significant improvement over methods reported in the literature for problems of this nature

Simulation oflow velocity impact oncomposite laminates with progressive failure analysis

In passive safety structures the use of composite materials has increased significantly recently due to their low specific mass and high energy absorption capacities. The purpose of this experimental study is to describe the macroscopic behaviors of different Kevlar woven composite materials with different kinds of matrix (pure and with acrylate based block copolymer additives: Nanostrength Ò ) under lowvelocity impact. Tests were performed with a drop weight tower on square plates (100 Â 100 mm 2 ) clamped by means of a circular fixture. Images were recorded during impact by a high-speed video camera fixed underneath the plate. It was found that Kevlar epoxy composite material with Nanostrength M52N has the best resistance to perforation.

Numerical study for the structural analysis of composite laminates subjected to low velocity impact

Composites Part B: Engineering, 2014

The paper deals with structural behaviour of laminated composite plates under low velocity impact loading conditions. The aim of the work is to develop numerical finite element models and simulation techniques to be implemented in a numerical procedure, which is aimed to improve designer forecasting capabilities of damaging resistance in composite structures. On the base of advanced material models and of selected failure criteria, the proposed numerical techniques can describe the damage initiation and propagation of impact damages in composite structures. A global/local finite element modeling approach has been proposed, in order to be able to develop explicit finite element analysis of the impact event, including damage initiation and propagation of both interlaminar and intralaminar damages. The same model has been analysed under quasi static compression conditions by taking into account, in a single explicit finite element analysis, both the impact and the after impact damages. For validation purpose, numerical results have been compared with data from two sessions of experimental impact tests, followed by compression after impact tests; the considered impact energy values are 50 J and 100 J respectively.

Discrete impact modeling of inter-and intra-laminar failure in composites

Dynamic Failure of Composite and Sandwich Structures, 2013

The goal of this study is to initiate a "test-calculation dialogue" on low velocity/low energy impact tests in laminated composites. The different types of impact damage developing during an impact test, i.e. matrix cracking, fiber failure, interface delamination and permanent indentation, are simulated. The bibliography shows a general lack of detailed validation of impact modeling and the originality of this work is to use refined and complementary experimental data to build and validate a numerical model. The good correlation between the model and this refined experimental database gave us relative confidence in the model, despite a few nonstandard material parameters. Permanent indentation was particularly focused and studied. Then we propose an original scenario to create permanent indentation, with a debris blocking phenomenon in the matrix cracks, as well as the corresponding model. The fiber failure model was set up using an original formulation between the integration points of the volume element in order to dissipate a constant energy release rate per unit area. Finally the model was used to evaluate the distribution of the dissipated energy among the different damage types, and demonstrated an interesting distribution between fiber failure and delamination.