Response Of Composite Laminates Research Articles

Dynamic simulation of composite layered plates reinforced by unidirectional fibers subjected low velocity impact

In the recent years a big focus is subjected to the response of structures subjected to out-of-plane loading such as blasts, impact, etc. not only to homogenous materials, but also to heterogeneous materials, such as composites. In the present study, low-velocity impact response of composite laminates was studied using ANSYS Workbench finite element code (FEM). The material of composite structure is orthotropic material reinforced by carbon fibers and have been taken from the Workbench material database. Plate consists of layers which are reinforced with unidirectional fibers in hexagonal and square array. Layer is considered as homogeneous transversely isotropic and layer stacking sequence is symmetrical or unsymmetrical.

Response of composite laminate with various cut-out combinations to tension load

All parts like adaptor plates, swash plates, repair patches and components providing way to wires have multiple cut-outs and as composites are replacing metals and alloys in many of these components it is necessary to understand the composite material’s reaction to mechanical loads in presence of cut-outs. In this work, experiments were conducted to note the impact of combination of various cut-outs on the UTS (ultimate tensile strength) of GFRC. Result shows that specimens containing combination of square and circular cut-outs can carry highest loads before failure as compared to other combinations.

Orthotropic node-separation finite element method for composite laminate in hypervelocity impact simulation

This paper reports a finite element modeling approach to simulate the hypervelocity impact (HVI) response of composite laminate. Node–separation finite element (NSFE) method based on scalar–element–fracture technique for isotropic material in HVI simulation has been presented in the previous study. To extend NSFE to composite materials, an orthotropic node-separation finite element (ONSFE) method is developed. This approach employs an orthotropic continuum material model and a corresponding orthotropic–element–fracture technique to represent the HVI behavior/damage of composite laminate. A series of HVI simulations are conducted and the developed ONSFE method is validated by comparing with the experimental data. The simulation results show that ONSFE can successfully capture the HVI phenomena of composite laminate, such as the orthotropic property, nonlinear shock response, perforation, fiber breakage and delamination. Finally, a HVI event of Whipple shield is simulated and the computational capability of ONSFE for predicting the damage state of the composite bumper is further evaluated.

Effect of Quasi-Static Loading on the Composite Laminates

The low velocity impact is a common phenomenon which occurs in fiber reinforced polymer composite products like LPG cylinders, fighter aircraft fuel drop tanks, aircraft wing surfaces, sports goods etc. The consequences of low velocity impact will create a considerable damage and ultimately lead to a premature failure of the structure. Hence the polymer composites for engineering applications must be provided with a better design solution. From the literature survey it is observed that, the response of composite laminates subjected to quasi-static loading, exhibits similar results as that of low velocity impact. Polymer reinforced composites are poor in damage tolerance with better strength to weight ratio than conventional materials. However composite materials can be tailored to meet the design requirements by manipulating fiber orientations and laminae stacking sequence. In the present paper, principles of classical laminate theory are considered for analysis. FEM is implemented for thorough understanding of the failure mechanism of each laminate by layer wise. Simulated quasi-static loading tests and observed the layer wise distribution of transverse strain intensity. The experimental setup is designed and fabricated as per ASTM D 6264 standards. The E-glass/epoxy composite laminate is quasi-statically loaded at its center by a steel ball indenter of diameter 8.7mm and its response is measured by the degree of opacity or translucency in terms of interlaminar and intra-laminar damage area. The stacking sequence of composite laminates are chosen as [00/600]12, [00/750]12 and [00/900]12. The damage areas obtained from numerical analysis are in good agreement with experimental results.

Investigation of two finite element modelling approaches for ballistic impact response of composite laminates

ABSTRACTWe evaluated two numerical modelling methods based on different modelling scales in simulating the ballistic performance of composite laminates. An orthogonal continuous material model was developed and used to establish an equivalent macro-scale impact model of a projectile/composite target (uniform model). Combining the Chang–Chang failure model and tiebreak contact algorithm, the corresponding computational model for the cross-plied microstructure of composite laminates was constructed layer by layer (layered model). Using the two modelling methods mentioned earlier, a series of ballistic impact simulations were carried out for Kevlar/epoxy composite laminates, and the simulation results were compared with the corresponding experimental results. The computational capacities of the two methods were compared in terms of damage pattern, ballistic limit, residual velocity and computational efficiency. The results indicate that the uniform model can simulate the main ballistic impact behaviour of composite materials, whereas the layered model can simulate more detailed features of composite damage. Moreover, the predictive capability of the uniform model for ballistic limit and residual velocity is equivalent to that of the layered model, and the uniform model exhibits a higher computational efficiency than the layered model.

Multi‐impact response of composite laminates with open holes

The multi‐impact response of glass‐epoxy composite laminates with open holes was studied. For this purpose, plates without any hole and containing one or two holes were tested under low velocity multi‐impact loading to assess the influence of holes on the damage development. Experimentally, it was verified that the maximum load and the dissipated energy decrease with the number of impacts, while the displacement increases for all cases. In addition, the presence of holes revealed to have an important influence on those parameters. A three‐dimensional finite element analysis including a cohesive mixed‐mode damage model was also performed to better evaluate the interaction between the resulting delamination and the presence of holes. It was observed that the existence of holes alters the delamination profile and contributes to increase its size especially in the case of two holes. It was concluded that special attention should be given to structural applications requiring open holes and eventually submitted to impact loads. POLYM. COMPOS., 39:2490–2498, 2018. © 2016 Society of Plastics Engineers

Random fatigue life prediction of carbon fibre-reinforced composite laminate based on hybrid time-frequency domain method

To evaluate fatigue life of composite laminate with hole under random loading, a random fatigue life prediction model is established by hybrid time-frequency domain method in this paper. Firstly, dynamic response of composite laminate is obtained from FE model in frequency domain. Secondly, root mean square of stress of six stress components of critical damage point in frequency domain are transferred to stresses in time domain. At last, 3D Tsai–Hill static failure criterion is adopted to convert the multiaxial stress into the uniaxial equivalent stress. Fatigue life is predicted by equivalent stress fatigue life code. The method is validated with the random vibration fatigue test of carbon fibre-reinforced composite laminate. Numerical results are compared with random fatigue experiments which show good agreement with numerical results.

Finite element modelling of the low velocity impact response of composite plates with block copolymer nano-reinforcements

The use of composite materials in passive safety structures has increased significantly due to their low specific mass and high energy absorption capacities. The purpose of this study is to develop and validate a macroscopic numerical model to simulate the impact response of composite laminates with nano-reinforcements. The impact resistance of laminate with Kevlar fibre reinforced epoxy resin embedded with Nanostrength®, an acrylate triblock copolymer that self-assembles in the nanometer scale is investigated. Low velocity impact experiments were performed on square plates clamped by means of a circular fixture using an instrumented drop tower. Images of the composite laminate during impact were recorded by a high-speed video camera fixed underneath the plate. An approach for modelling these composites in the commercial finite element code LS-Dyna using constitutive model based on the theory of continuum damage mechanics developed by Matzenmiller, Lubliner and Taylor - called MLT model - is presented. LAMINATED COMPOSITE FABRIC material model, available in the LS-Dyna material model library as (MAT58), was chosen for modelling the low velocity impact of the Kevlar composite plate. The model requires input of material properties in shear, tension, and compression to define stress-strain behaviour within the laminate. The parameters needed for the model are determined using a combination of experimental tests and parametric analysis. The macroscopic response of the Kevlar composite with and without nanoparticles in the resin subjected to impact loading are simulated in LS-Dyna with the phenomenological material model, and is validated by comparison with experiments. It was found that the Kevlar epoxy composite material with Nanostrength M52N had better resistance to perforation compared to the lamiante with neat resin.

Response of Fiber Reinforced Composite Structures to Ballistic Loads

Explosion and high velocity impact are typical ballistic loads of structures. This paper describes the problem of wave propagation in solid rocket booster part. Such waves originate by acting of explosion waves or by high velocity impact of solid parts on the structure. Computational simulations are applied to the problem of propagation of shock waves in a composite material reinforced by carbon fibres which are supposed to be much stiffer than the matrix. The shock wave in such material is influenced by reflexion and refraction on the interface between fibres and the matrix and by the interaction of then waves. The shock wave is strongly damped in such composites in this way. In the present study, the response of composite laminates under velocity impact loading will be investigated using MATLAB and ABAQUS software.

TEMPERATURE EFFECT OF LOW VELOCITY IMPACT RESISTANCE OF GLASS/EPOXY LAMINATES

This paper aims to evaluate the effect of temperature on impact damage resistance of glass/epoxy laminates. A series of impact tests were performed using an instrumented impact-testing machine at temperature ranging from -40°C to +80°C. The resulting impact damage was measured using back light method. The impact resistance parameters were employed to understand the damage resistance. It was observed that temperature has a little effect on the impact responses of composite laminates. The damage resistance of glass/epoxy laminates is somewhat deteriorated at two opposite extremes of the studied temperature range and this behavior is likely due to the property change of glass/epoxy laminates under extreme temperatures

Three-dimensional nonlinear analyses of scarf repair in composite laminates and sandwich panels

A special-purpose analysis tool based on the finite element method is presented for parametric design studies of composite laminates and sandwich panels with scarf repairs. This design tool provides the complete three-dimensional stress and strain fields in scarf-repaired panels without any requirements on the nature of the lamination and the type of loading. The adherends are modeled using a plate element based on a higher-order single-layer theory, and the adhesive is modeled using a solid element. The higher-order nature of the plate theory makes it suitable for analyzing thick laminates and sandwich panels comprised of numerous plies. The model takes into account geometric nonlinearity in the adherends and assumes a bilinear stress-strain relationship for the adhesive. The responses of composite laminates with single- and double-sided repairs and sandwich panels with both full and partial repairs of the top face sheets are investigated.

Dynamics of thick hygrothermal viscoelastic composite laminates through finite element method

An uncoupled computational model for analyzing the hygrothermal dynamic response of composite laminates has been developed. The constitutive equations, expressed in an integral form, and involving relaxation moduli are adopted, to describe the non-aging hygrothermorheologically simple materials. A Prony series represents the relaxation moduli is exploited in order to derive a recursive relationship, and thereby eliminate the storage problem that arises when dealing with material possessing memory. The problem is formulated in a descritized variational form. Mindlin and higher order finite elements are employed for spatial descretization, while the Newmark average acceleration scheme is exploited for temporal descritization. The adopted recursive formula uses only the details of the previous event to compute the details of the current one. Numerical results of the displacement fields of both thin and thick viscoelastic laminates problems are discussed to show up the effectiveness of Mindlin and higher-order shear theories.

OPTIMIZATION CONTROL OF COMPOSITE LAMINATES FOR MAXIMUM THERMAL BUCKLING AND MINIMUM VIBRATIONAL RESPONSE

The problem of maximizing the thermal buckling and minimizing the vibrational response of composite laminates is solved using optimal design and active control procedures. The problem is formulated based on a first-order shear deformation laminate theory with various cases of boundary conditions. The design objective is to maximize thermal buckling using ply thickness and the fiber orientation angle as design variables. The active control objective is to minimize the laminate vibrational response with the minimum possible expenditure of control energy. The vibrational response is expressed in terms of the total elastic energy of the laminate and a penalty functional of closed-loop control force. Liapunov-Bellman theory is used to obtain solutions for controlled deflections and optimal control force. Comparative examples are given for angle-ply antisymmetric laminates subjected to a uniform temperature distribution. A general representation for the design variables is presented such that the ply thickness is a function of the number of layers. Some of the obtained numerical results are compared with their counterparts in the literature.

Effects of joining techniques on impact perforation resistance of assembled composite plates

A previous study on impact response of composite laminates concluded that impact perforation was the most important damage stage in composite laminates subjected to impact loading, since impact characteristics (peak force, contact duration and absorbed energy) and mechanical properties degradation of composite laminates reached critical points once perforation took place. It was also found that thickness had a greater influence on impact perforation resistance than did in-plane dimensions. However, as the composite laminates became very thick, the manufacturing cost for obtaining high-quality composite laminates increased. In an effort to meet design requirements and reduce manufacturing costs, assembled composite plates, which were organized by assembling multiple thin composite laminates, were considered as alternatives for thick single-laminate composite plates. Various joining techniques including mechanical riveting, adhesive bonding and stitch joining, and their combinations, were used in assembling two- and three-laminate plates. Experimental results revealed that adhesive bonding outperformed other joining techniques. Although good bonding resulted in higher joining (bending) stiffness and subsequently higher perforation thresholds, increasing the laminate thickness or the number of laminates was found to be more efficient in raising perforation threshold than in improving the joining stiffness. The assembled three-laminate plates were found to have higher perforation thresholds than their thick single-laminate counterpart.

On the viscoelastic response of composite laminates

The present work deals with the determination of theviscoelastic properties of composite laminates based on the viscoelasticbehaviour of the single lamina. A viscoelastic lamination theory isdeveloped assuming that the lamina stiffness matrix is fully complex andfrequency dependent.

Integral equation approach to composite laminate analysis

A comprehensive integral equation based approach is presented to determine the elastic response of composite laminates under axial, bending, shear/bending and torsional loadings. The integral equations governing the laminate behavior are directly deduced from the reciprocity theorem for beam‐type structures by employing the fundamental solution of generalized plain strain anisotropic problems. Taking into account the displacement and stress continuity along the interfaces and the external boundary conditions the formulation is numerically solved by the multidomain boundary element method. The resolving system of linear algebraic equations is solved to provide the solution of the problem in terms of displacements and tractions on the boundary of each ply within the laminate. Once this boundary elastic response is determined the displacements and stresses at any point of the laminate can be computed using the appropriate boundary integral representations. The approach, based on a pointwise formulation, makes it possible to analyze laminates with the widest generalities as regards the section shape and lay‐up. Some applications are presented in order to demonstrate the accuracy and effectiveness of the method proposed.

Impact analysis of composite laminates with multiple delaminations

This paper concerns with the transient response of composite laminates with multiple delaminations subjected to low-velocity impact by a rigid ball. The finite element method based on the Mindlin plate theory is employed to describe the motion and deformation of the laminates. A Hertzian-type indentation law is adopted to calculate the impact force between the laminates and the rigid ball. To deal with the dynamic contacts between delaminated layers effectively, a modified Lagrange multiplier technique is employed. For multi-body dynamic contacts, the computation of contact force between delaminated layers is addressed. Numerical results provide much information for understanding the impact phenomenon of the composite laminates with multiple delaminations.

Response of Composite Laminates on Impact of High Velocity Projectiles

Response of Composite Laminates on Impact of High Velocity Projectiles

INNOVATIONS FORUM: Development of Cement-Based Cross-Ply Laminates by Filament Winding Technique

A filament winding system was developed for manufacturing cross ply composites using continuous fibers. The computer controlled system is used for manufacturing composite laminates, pipes, and pultruded sections. The electrical and mechanical components of the system are discussed. The software/hardware system may be easily adopted for design of and manufacturing of full scale composite laminate systems. Cement based composite laminates are manufactured using continuous glass fibers. Mechanical response of composite laminates are measured using closed loop uniaxial tensile and flexural tests. Results indicate that tensile strength of composites can exceed 50 MPa using 5% alkali-resistant (AR) glass fibers. Through varying the stacking sequences, the ultimate strain capacity can be increased to more than 2%.

Process Simulation in Thermoset Composites for Cure Response and Stress Prediction

A process simulation model was developed to predict the cure response and temperature gradients that occur in composite laminates during fabrication. Manufacturing processes for corrosion resistant composites can be designed using the model. A one-dimensional heat transfer analysis was used to simulate composite cure. Cure response factors such as the lay-up process, temperature boundary conditions, and the heat generated due to exothermic reaction were considered. The predicted temperature and resin cure gradients can be used to determine residual stresses that cause cracking. The cure kinetic response and resin shrinkage of a vinyl ester resin were characterized. The effect of partial resin cure caused by low curing temperatures was included in the kinetics model. A computer program was developed to predict the cure response in composite laminates. Temperature response predictions agreed well with results obtained from experiments on a composite nozzle. The process model was used to study the effect of laminate thickness, ambient temperatures, and air cooling on laminate cure response. Residual stresses in the nozzle due to cure temperatures were determined using finite element analysis.