Impact Response Of Composite Plates Research Articles

Characterization of delamination effects on free vibration and impact response of composite plates resting on visco-Pasternak foundations

In this study, the free vibration and impact response of composite plates with interfacial delamination are investigated based on the improved layerwise theory with finite element implementation. The interaction between the composite plate and the surrounding medium is simulated by the visco‐Pasternak foundation model. Hamilton's principle is used to derive the equations of motion for the delaminated composite plates. The impact responses of the delaminated composite plates are later solved by the Newmark algorithm for both clamped-free (C-F) and clamped-clamped (CC) boundary conditions. Influence of the foundation parameters, damping parameter, longitudinal and interfacial delamination locations on eigenfrequencies and transient history are investigated and discussed. Numerical results illustrate that delamination reduces the natural frequencies and the middle plane delamination possesses the largest damage effect. With a stiffer foundation, the damped eigenfrequencies increase significantly and the transient responses also converge much faster. Moreover, the existence of delamination affects the higher frequencies dramatically which may further help identify delamination locations in composite plates resting on visco-Pasternak foundations for structural health monitoring.

Assessment of Different Mathematical Models for Analysis of Low-Velocity Impact on Composite Plates in Presence of Pre-loads

In this paper, the low-velocity impact response of composite plates in the presence of pre-loads is investigated using three new models for contact force estimation. The boundary conditions are considered as simply supported and the behavior of the material is linear elastic. The equations are based on both classical and first order shear deformation theory and the Fourier series method is used to solve the governing equations. The mass of the impactor is considered to be large mass and therefore the impact response is categorized as quasi-static. In the first impact model, the contact force history is first considered as a half-sine and then the maximum contact force and contact duration are calculated. In the second model, an improved two degree of freedom (ITDOF) spring-mass system is expressed by calculating the effective contact stiffness using a fast-iterative scheme. In the third model, which is expressed for the first time in this paper, the plate is considered as a series of masses and springs constructing a multi degree of freedom (MDOF) spring-mass system and the average forces applied to springs is introduced as the contact force. Validation of these models is done by comparing the results with the analytical, numerical and experimental results and shows good agreement. Results show that the new MDOF spring-mass system is more accurate for calculating the contact force rather than the ITDOF spring-mass system.

Response of fabric insert injection overmolding PP based composites subjected to single and muti-impact

This paper presents the results of a current study on the development and impact response of composite plates manufactured by injection overmolding on the two sides of a single reinforcement fibre mat. The injection polymer is a talc-filled polypropylene, nowadays used for structural purposes. Three configurations with different insert fibre mats were used: Kevlar, biaxial and multiaxial glass fibre mats. The parameters studied were the fibre mat type and the impact energy. For single impact tests, it was concluded that the highest impact energy required to achieve impactor perforation is obtained with Kevlar insert, while the highest percentage of energy recovered is achieved with biaxial glass fibre netting. Kevlar insert also allows for the maximum impact stiffness. For the multi-impact tests, the recovered energy and the dynamic stiffness show the same tendencies of the single impact tests. On low energy impacts, the effect of the insert fibre and of the previous impact are quite reduced, while for impact energies above 6J, previous impacts reduce significantly the recovered energy and the impact energy for which the perforation was achieved.

Effect of tensile preloading on the ballistic properties of GFRP

This paper focuses on a ballistic impact response of composite plates with a thickness of 2 mm subjected to uniaxial tension preload. It also presents experimental and numerical results of ballistic impact response studying. To generate impact damages by a spherical projectile in the range of 100–800 m/s velocities the powder gun stand was used. During the experiments, the ballistic stand was placed in an INSTRON 5882 testing machine for setting five different states of preloading. The results showed that uniaxial tension preload reduces the ballistic limit. Higher tensile preload levels were found out to lead to the smaller delamination area. This is a result of impact energy dissipation in inclined (and damaged during pretension) segments of threads which play the role of dry friction contact areas between fibres. The response time to the rupture of the specimen after penetration depends on a preload level, which was observed as another phenomenon. The finite element simulations of preloaded plates subjected to ballistic impact were carried out using ANSYS Workbench (AUTODYN3D) explicit package. As numerical results were in good agreement with the experimental data, a variation of GFRP ballistic limit with tension up to 92% of strength was numerically investigated.

Modelling the in-plane strain rate dependent behaviour of woven composites with special emphasis on the non-linear shear response

A constitutive model for the rate dependent mechanical behaviour of woven composites is presented. A glass fibre composite was experimentally characterised under quasi-static and dynamic regimes to determine the strain rate dependency. Afterwards, the physical findings were used to develop a constitutive model able to predict strain rate dependent phenomena. A continuum damage mechanics approach was implemented to capture the composite failure and strain rate dependency was incorporated in the ply properties together with a damping algorithm for stability purposes. As a result, the model provided strain rate dependent behaviour while ensuring the stability of the numerical simulations. Finally, the model was used to investigate the low velocity impact response of composite plates, showing the importance of considering the strain rate dependency even at medium rates to accurately predict the response laminates subjected to dynamic loads.

Finite element analysis for the evaluation of the low-velocity impact response of a composite plate

The low-velocity impact responses of cross-ply CFRP composite plates are investigated experimentally and are simulated using the finite element code LS-DYNA. An experimental test was initially performed and two different modeling approaches were then employed to model the composite plates. In the first numerical modeling approach, solid elements are utilized for the composite layers, whereas in the second, shell elements are used. The numerical model using the shell elements shows a good correlation with the experimental results, while the impact damage in the form of delamination is predicted more precisely using solid elements.

Effects of static preloads on the high velocity impact response of composite plates

The paper discusses a high velocity impact scenario where representative fuselage composite plates are statically preloaded and then impacted with a blunt impactor at velocities in the range 70–105m/s. Compression and tension preloads that represent design limit load were considered as well as lower preloads that a structure would carry more frequently. Gas gun impact tests were performed to generate a validation database for comparison with results from numerical simulation. A modelling methodology to simulate preloads and transient impact events was documented. The numerical model captures intra- and inter-ply damage by using layers of shell elements connected with cohesive interface layers. Both test and simulation results indicate an influence of static preloads on the impact damage response. The numerical model was especially used to better understand the interaction between preloads and dynamic impact loads which are complex especially for impact on buckled plates.

Refined constitutive, bridging, and contact laws for including effects of the impact-induced temperature rise in impact responses of composite plates with embedded SMA wires

In the present research, effects of the impact-induced temperature rise on the phase transformation of shape memory alloy (SMA) wires embedded in composite plates and consequently, impact responses of the hybrid plates are investigated, for the first time. In the available approaches, effects of the temperature rise have been studied only for single SMA wires under uniaxial tensile loads whereas the stress and martensite volume fraction vary along the SMA wires embedded in a hybrid composite plate under transverse impact. The impact-induced heat of the SMA wires is determined based on proposing a refined free energy function that includes the latent heat of the phase transformation. Furthermore, Brinson's constitutive law of the superelastic SMAs and Hertz contact law are revised based on the refined phase version of the free energy function and a proper bridging law wherein, distributions of the SMA phases are considered to be both localized and time-dependent. Results of the employed bridging law are more accurate than those of the common homogenization techniques wherein, stresses of the wires cannot be easily distinguished from those of the mixture. The resulting governing equations are solved by the finite element method and the refined nonlinear constitutive laws are solved through a return-mapping Newton-Raphson procedure, within each time step. Results reveal that incorporation of the realistic heat generation phenomenon leads to remarkably higher local stresses; a fact that has to be considered in the design stage.

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.

Impact response of thick composite plates under uniaxial tensile preloading

This work focuses on the impact response of composite plates 5mm thick subjected to uniaxial tension preload. Laminated carbon/epoxy with quasi-isotropic stacking sequence ([0/45/90/-45]2)S samples were used. Doehlert-type design of experiments was proposed to investigate the influence of both preload and impact energy on impact composite responses. Deformation, varying from 300 to 3000 micro-strain, was imposed thanks to a preload device designed for this purpose. Impacts were generated using a home made drop tower. Imposed impact energy was varying from 30 to 214J. Post-impact damage was characterized by both non-destructive (ultrasound) and destructive (deply) techniques. Influence of the preloading on delamination areas (total and projected) was quantified and found sensitive to the preloading.

Impact response of composite plates manufactured with stitch-bonded non-crimp glass fiber fabrics

Abstract This experimental study deals with the impact response of composite plates manufactured with stitch-bonded non-crimp glass fiber fabrics. Three kinds of fabrics – biaxial, triaxial, and quadraxial – are used as reinforcing material. Polyester resin is used as a matrix material in the composition of composite plates. An instrumented drop weight impact testing machine, Instron-Dynatup 9250 HV, is used for impact testing. Impact tests are performed under various impact energies, ranging from damage initiation to final perforation. An energy profiling method, showing the relation between impact energy and absorbed energy, was used together with load-deflection curves to determine the penetration and perforation thresholds of those composites. The failure processes of damaged specimens for different impact energies were evaluated by comparing load-deflection curves and images of damaged samples taken from the impacted and non-impacted sides. All types of composites have obvious penetration and perforation thresholds. The perforation threshold of triaxial/polyester composite is approximately 27% and 22% higher than that of the quadraxial and biaxial/polyester composites, respectively.

An experimental investigation on the low velocity impact response of composite plates repaired by VARIM and hand lay-up processes

This paper presents results of an experimental investigation on the impact response of repaired and unrepaired glass/epoxy composite plates. Repaired samples were prepared by two different manufacturing methods; vacuum assisted resin infusion process and hand lay-up technique. In order to compare impact response of the repaired and unrepaired samples a number of single impact tests were performed under various impact energies. Damage process of the samples is analyzed from cross-examining load–deflection curves and damaged specimens. From the visual inspection, for the impacted side of the samples, it is noted that the main damage modes for repaired samples are matrix and fiber cracks around point of impact and delaminations while severe matrix cracks expanded through fiber directions are the dominant damage mode for unrepaired samples. At the back surfaces, delaminations and fiber–matrix debonding oriented in the fiber directions are observed for unrepaired samples. However, for repaired samples the fiber fractures through repair line as well as the delaminations become dominant modes. For a reasoning justification in discussing impact test results, interlaminar fracture toughness (Mode I and Mode II) and flexural tests for repaired and non-repaired samples were also conducted.

Impact Response Characterization in Composite Plates—Experimental Validation

This paper presents an experimental study for the normalized low-velocity impact response of composite plates. It is demonstrated that a characterization diagram that shows the relationship of three non-dimensional parameters with the normalized maximum impact force can be used to fully characterize the response. With the governing non-dimensional parameters obtained experimentally, it is shown that impact tests having the same non-dimensional parameters, have dynamic similarity and the same non-dimensional response. Furthermore, the experiments can be placed in appropriate dynamic regions in which simplified dynamic models can be used to predict the response.

Limits of asymptotic solutions in low-velocity impact of composite plates

This paper presents a study of the low velocity impact response of composite plates by using dimensional analysis and lumped-parameter models. Simple analytical expressions are obtained and used to construct a characterization diagram that shows the relationship between the maximum normalized impact force and two non-dimensional parameters. For a given impact event, it is shown that the non-dimensional parameters can be obtained by analytical, computational or experimental methods. Once these parameters are determined, the characterization diagram can be used to estimate the type of response, and maximum impact force. Furthermore, the diagram can be used to select adequate simple models for a given impact situation. It is shown that these simple models provide very good approximations of the impact response for a pre-determined wide range of impact parameters.

Modified SDOF Models for Improved Representation of the Impact Response of Composite Plates

Previous research has shown that simple single degree of freedom (SDOF) models can be used successfully to reproduce the force-time response of composite plates subjected to low-velocity impacts (LVI). In particular, a simple spring-mass (SM) model yields accurate estimates of the peak contact force as a function of impact energy. The major limitation of this model is that it applies only to elastic impact events, and ceases to be valid after the onset of damage. The effort of this investigation is to modify the SM model, while retaining the simplicity of its formulation, and to extend its range of validity to the super-critical regime. Three models are derived, namely the damaged stiffness, the dissipated energy, and the spring-mass-dashpot models, and their validity is examined through comparisons with experimental data. Impact force-time traces for carbon/epoxy laminates exhibiting various combinations of laminate thickness and support span are collected, and it is found that the additional unknowns introduced for each of the models, although determined empirically, are strongly related to the structural parameters for each configuration investigated.

Enhanced Evaluation of the Low-Velocity Impact Response of Composite Plates

Recent research programs conducted on low-velocity impact events on composite structures have used force as the sole governing parameter and based their damage resistance and tolerance considerations on the peak recorded value. Understanding of other available parameters, such as contact duration and coefficient of restitution, which are related to the effective structural stiffness of the target, is fundamental in the design of a methodology for assessing impact performance and can offer greater insight in the interpretation of future research programs. An experimental database is gathered through drop tower impact testing by means of a rigid striker on clamped circular plates, for a particular polymer composite system. Several researchers have presented data showing that a critical value of the impact force for the onset of damage exists. Structural properties are hereby studied in both the sub- and supercritical regimes, which means for impact energy values below and above the damage threshold. A modified approach to the classic spring‐mass model, which employs the notions of damaged stiffness and dissipated energy, leads to the derivation of approximate formulas that describe the peak force-energy curve. In particular, the introduction of a dashpot to simulate the effect of damage greatly improves the accuracy of the model in the regime beyond the structural integrity threshold. A novel method to assess the residual performance of the damaged plate is developed, and it consists in low-energy, nondestructive impact testing, the results from which bear a striking resemblance with the curves obtained by compression after impact. MPACT tests can prove inherently difficult to understand because of the large number of parameters that play a key role in such events, particularly in the case of laminated composite structures due to their heterogeneous anisotropic nature and the complex failure modes that can occur. The current experimental investigation is conducted on square plates, supported over circular openings, having a quasi-isotropic [0/90/±45]4s stacking sequence. Such a configuration benefits from the axial symmetry of the circular geometry and the low degree of anisotropy of the laminate and thus facilitates the concentration on the mechanics of the impact event and the complex failure mechanisms. An extensive literature review has indicated that many questions still surround the impact response of composite plates. In particular, an ongoing debate exists on whether force or energy should be used to compare impact test results on different configurations, as well as whether a force- or energy-based criterion should be employed to predict the structural integrity threshold or uniquely and satisfactorily assess the state of damage in the plate. The aim of this paper is to show how governing parameters, such as force, energy, and structural stiffness vary between the subcritical and supercritical regimes and that peak force, although extremely valuable for predicting the damage threshold, cannot be used independently for investigating the impact performance of a composite structure. The use of an instrumented drop tower such as the General Re

Impact Response of Adaptive Piezoelectric Laminated Plates

Semi-analytical models for the impact response of composite plates having distributed active and sensory piezoelectric layers are presented. An exact Ritz model is utilized based on a mixed-e eld piezoelectric laminate theory thatencompassesbothdisplacementandelectricdisplacemente eldsthroughthelaminate.Thegoverningequations of motion of a simply supported plate and a low-velocity impactor are formulated including impactor dynamics and contact law. State feedback linear quadratic regulator and output feedback controllers are implemented to actively reduce impact force. Numerical results quantify the electromechanical response of a composite plate with piezoelectric sensors impacted by three different mass impactors. The impact response of an actively controlled plate is also shown, and the possibility to improve critical impact parameters is demonstrated.

Corrigendum to “Mass criterion for wave controlled impact response of composite plates” [Composites: Part A 31 (2000) 879-887

Corrigendum to “Mass criterion for wave controlled impact response of composite plates” [Composites: Part A 31 (2000) 879-887

Mass criterion for wave controlled impact response of composite plates

Abstract Impact duration strongly influences the impact response of plates. Long impacts cause a quasi-static response influenced by the plate size and boundary conditions. Short impacts cause a response governed by wave propagation unaffected of plate size and boundary conditions. This paper shows that the response type is governed by the impactor–plate mass ratio and not by impact velocity and derives a criterion for small-mass (wave controlled) impact response of orthotropic plates. Published criteria for large-mass (quasi-static) impact are discussed. Small-mass impacts on composite laminates are shown to be more critical than large-mass impacts of the same energy. Use of mass criteria for selecting analytical response models and considerations for sandwich plates are also discussed.

Characterization of impact in composite plates

The nature of impact response of composite plates is studied through normalization of the governing equations. The key parameters which govern the transition from locally dominated to globally dominated responses are identified and used to characterize the impact response. Numerical and experimental results show that the type of response can be predicted through a functional relationship of the normalized impact force and two nondimensional parameters.