Damage Behavior Of Composite Materials Research Articles

A Bond-Based Peridynamic Model with Matrix Plasticity for Impact Damage Analysis of Composite Materials

The prediction of damage and failure to fiber-reinforced polymer composites in extreme environments, particularly when subjected to impact loading, is a crucial issue for the application and design of protective structures. In this paper, based on the prototype microelastic brittle (PMB) model and the LaRC05 composite materials failure model, we proposed a bond-based peridynamic (BB-PD) model with the introduction of plastic hardening of the resin matrix for fiber-reinforced polymer composites. The PD constitutive relationships of the matrix bond and interlayer bond under compressive loading are considered to include two stages of linear elasticity and plastic hardening, according to the stress-strain relationship of the resin matrix in the LaRC05 failure model. The proposed PD model is employed to simulate the damage behaviors of laminated composites subjected to impact loading. The corresponding ballistic impact tests of composite laminates were carried out to observe their damage behaviors. The PD prediction results are in good agreement with the ballistic experimental results, which can verify the correctness and accuracy of the PD model developed in this study in describing the impact damage behaviors of composite materials. In addition, the characteristics and degree of damage in composite laminates are analyzed and discussed based on this PD model. The difference in the impact resistance of composite laminates with different stacking sequences is also studied using the numerical simulation results.

Damage detection in bio-polyamide 11/woven basalt fibres composite laminates subjected to dynamic events

The complexity of the damage behavior of composite materials due to the simultaneous evolution of different mechanisms involving matrixes, reinforcements and interfaces is a topic which, despite decades of knowledge, still requires specific insights and is the subject of a multitude of researches. Recently, with the attention increasingly directed towards biobased raw materials, these aspects have shown a renewed interest, prompting the need for further contributions. In this context, this experimental research work aims to investigate the damage behavior of laminate structures based on a commercial polyamide obtained from castor oil, reinforced with woven basalt fibers. The focus was on samples obtained by hot compaction using two different pressure profiles and subjected to low velocity impacts with different impact energies. Damage analysis was performed on impacted specimens using ultrasonic phased array inspections and pulsed thermography. The non-destructive analysis supported low velocity impact test results, confirming the different contribution of the damage mechanisms involved, as expected from the different level of compaction of the materials, in turn due to diverse manufacturing conditions. This research has emphasized the complementarity and effectiveness of these two non-destructive characterization techniques, providing potentially useable results for the optimal design and manufacturing of biocomposite systems.

A developed energy-dependent model for studying thermal shock damage and phase transition of composite reinforced panel subjected to lightning strike

Lightning strikes generate large amounts of energy. Thus, composite structures subjected to lightning strikes undergo significant physicochemical changes. In this study, the thermal shock damage and three-phase transition of a composite reinforced panel were investigated through a numerical simulation, an experiment, and ultrasonic C-scanning. An anisotropic constitutive model and PUFF equation of state (EOS) were proposed to study the damage behaviors of composite materials. The dynamical damage behaviors and three-phase transition of the composite reinforced panel were simulated using the proposed constitutive model and PUFF EOS. Finally, a lightning experiment and ultrasonic C-scanning were conducted to validate the numerical results. Obvious fiber upwarping and swelling were observed in the numerical simulation. The melted and vaporized materials caused a reverse thermal shock effect, which led to concave pits, buckling and internal damages in the composite reinforced panel. The numerical results were compared with experimental results and scanning results to validate that the proposed constitutive model and modified PUFF EOS can be well used to simulate the dynamical damage behaviors of composite materials. The simulated damage behaviors of the composite reinforced panel agreed well with the behaviors observed in the experiment.

In-situ computer tomography for analyzing the effect of voids on the damage behavior of composite materials

Due to their high specific stiffness and strength composites are ideally suited for applications in machine building, vehicle constructions, wind power technology and aviation. In the manufacture of composite structures voids are an unavoidable fact. Several non-destructive techniques are potentially able of detecting defects, but only the exact knowledge of the effects of defects on the mechanical properties allows the definition of thresholds for the purpose of quality management. Here, an experimental program for characterizing the effect of voids on the damage behaviour is presented. Flat specimens with glass fibre non-crimp fabric reinforcement and epoxy matrix (GF-NCF/EP) are produced using vacuum assisted resin transfer moulding. By means of a specific adjustment of the process parameters, test specimens with three different void contents are produced and compared. For detailed analysis of damage evolution in the vicinity of voids, in-situ computed tomography (in-situ CT) is used, for the volumetric visualization of the material during tensile loading.

Validation of fatigue damage model for composites made of various fiber types and configurations

Empirical model for predicting fatigue damage behavior of composite materials developed recently has been applied to composite materials made of different fibers in various configurations: carbon and glass fiber noncrimp fabric reinforced epoxy composites, chopped strand mat glass fiber-reinforced polyester composites, randomly oriented nonwoven hemp fiber-reinforced polyester composites, and glass/hemp fiber-reinforced polyester hybrid composites. The fatigue properties were evaluated in tension–tension mode at stress ratio R = 0.1 and frequency of 1 Hz. The experimental fatigue data were used to determine the material parameters required for the model. It has been found that the model accurately predicts the degradation of fatigue life of composites with an increase in number of fatigue cycles. The scope of applicability of this model has thus been broadened by using the fatigue data of natural fiber and noncrimp fabric composites.

Direct identification of nonlinear damage behavior of composite materials using the constitutive equation gap method

This paper aims at improving the reliability of the identification of parameters that govern a non-linear damage law for orthotropic materials, the non-linearity considered being due to the inherent damage induced by in-plane shear loading. The adopted identification technique is based on the minimization of the constitutive equation gap (CEG). It is built upon the quadratic deviation between the measured and computed strain field. The paper explains how an appropriate use of the CEG method can improve the identification of material model parameters from strain field measured by an optical technique of full-field measurement. The minimization problem is solved by the modified Levenberg–Marquardt method. In the present work, the experimental data are replaced by numerical ones provided by the finite element (FE) simulations. These latter are performed on an orthotropic glass/epoxy composite material. The obtained parameters based on these numerical data are considered as reference ones. A sensitivity analysis is proposed as an attempt to examine the influence of some parameters, among which the mesh refinement, the initial set of parameters, the experimental noise, and the orthotropy ratio. Two types of noise simulating the measurement errors are tested: a random noise simulated by a Gaussian white noise and a bias noise. The obtained results demonstrated the feasibility and applications of the proposed method. The use of the CEG method gives results of good quality.

Rate-dependent damage model for polymeric composites under in-plane shear dynamic loading

The present study aims at rate-dependent damage modeling for polymeric composite materials with the rate-dependent constitutive model using a multi-scale approach. Phenomenologically, the nonlinear response of a composite under the in-plane shear loading condition is originated from the viscoplasticity of a matrix and the damage behavior of composite materials. In case of dynamic loading conditions, the strain-rate effects the change of the damage behavior of composite materials, as well as the behavior of the matrix. The enhanced micromechanical model which improves the in-plane shear behavior, is used for analyzing the rate-dependent behaviors of the fiber and matrix constituents. The rate-dependent elastic damage model based on orthotropic continuum damage mechanics theory at the macromechanical level is applied to improve the accuracy of the analysis model. Predictions by presented model are shown to agree fairly well with experimental results over a wide range of strain rates.

Analysis of Inelasticity Effect Due to Damage on Stress Distributions in Composite Laminates

A damage mechanics model characterizing damage behavior of composite materials proposed earlier by the authors is employed to analyze the damage effects on stress field near the free edge in symmetrically laminated graphite/epoxy composites of finite dimensions under umaxial tension. A quasi-three-dimensional finite element analy sis is developed for the present investigation. The results from the damaged and undam aged stress distributions of [0/90°] s, [90/0°] s, and [±45°] s laminates are compared and examined. The processes of initiation and development of damage zone in these composite laminates are also discussed.