Impact Response Of Composite Laminates Research Articles

Improving the impact resistance and damage tolerance of fibre reinforced composites: A review

As the use of composite laminates are unceasingly increasing more and more in many applications, the in-depth understanding about the impact response of composite laminates in certain areas like sport, aerospace and automotive has gained more attention of the designers and scientists over the last two decades. The authors have focused to review the impact properties of fibre reinforced composites particularly impact damage tolerance. Impact resistance, damage tolerance, composite failure and methods of assessing damage tolerance are presented. Furthermore, the approaches for improving damage tolerance such as fibre architectures resin system, and hybridisation using either yarn hybridisation or hybrid layers are discussed. In the end, a survey of modelling the impact damage of laminated composites is made by considering the inter-laminar and intra-laminar failures as key point for evaluating the response of laminates under impact loading.

Influence of various damage mechanisms on the low‐velocity impact response of composite laminates

AbstractThis study exhibits the effect of different damage mechanisms on the mechanical behavior of composite laminates subjected to low‐velocity impact load. To achieve this, seven low‐velocity impact energies were applied to laminates with five different thicknesses and four unique stacking sequences. The extent of damage was quantitatively evaluated through contact measurements and ultrasonic C‐scan techniques. Numerical simulations, showing good agreement with experimental results, characterized the distribution and evolution of damage within the laminates. The findings reveal that when matrix and delamination damage are predominant, the dent depth increases slowly and is visually invisible, while the delamination area expands almost linearly. Conversely, When fiber damage prevails, the laminate absorbs more energy, leading to rapid increases in dent depth, the appearance of visible cracks, and the occurrence of sharp fluctuations with multiple peaks in contact force and displacement curves. Nonetheless, the delamination area and projection tend to be stable and unchanged. Furthermore, alterations in thickness and stacking sequence directly affect the damage characteristics and energy absorption properties. This research offers valuable theoretical insights and serves as a reference for enhancing the comprehension of the failure mechanism of laminates and optimizing their performance.Highlights Demonstrate the utility of dent depth in identifying changes in damage mechanisms. Evaluate the delamination damage of laminates after impacts by ultrasonic C‐scan techniques. Reveal the regulation of impact response parameters for different damage mechanisms. Investigate the effect of variation in thickness on damage characteristics and energy absorption. Evaluate the impact resistance of laminates with different stacking sequences.

Numerical study of the simultaneous multiple impact phenomenon on CFRP plates

Composite laminates are currently used in various fields of engineering, in which they can be subjected to multiple impacts, reducing their service life. Typical examples of these phenomena are found in the high-speed rail industry. Several works have focused on this topic, but very few have exposed a methodology that verifies the existence of stress wave interaction, produced by the action of several projectiles that impact on a structure simultaneously. Therefore, this work aims to study the multiple impact response of composite laminates, as well as the influence of stress waves on their mechanical behaviour. For this purpose, a numerical multiple impact model was developed. This numerical model was validated with single impact experimental results taken from the literature. It was observed that the presence of more than one projectile in the impact event reduced the ballistic limit of composite laminate. Finally, it was concluded that stress waves influenced the impact response of CFRP plates.

Simulation and Experiment on the Low-Velocity Impact Response of Flax Fabric Reinforced Composites.

Natural fiber reinforced composites are increasingly used to fabricate structural components prone to suffering low-velocity impacts. The low-velocity impact response of flax fabric reinforced composites under different impact energies is experimentally studied and numerically simulated. A multi-scale finite element analysis strategy for the progressive damage prediction of flax fabric reinforced composites is developed. Micro- and meso-scale analyses are conducted to predict the effective properties of the woven unit cell. Macro-scale analysis is carried out subsequently to predict the impact response of composite laminates using the results of micro- and meso-scale analyses as inputs. Simulation results and experimental results both show that most of the impact energy is absorbed by the specimens when the impact energy is lower than 4 J, and the absorption ratio of impact energy slightly increases with the increase in impact energy. On the contrary, a dramatic decrease occurs in the absorption ratio when the impact energy is 6 J, due to the severe damage to the specimen. In addition, simulation results indicate that matrix shear damage and interlaminar damage are the primary failure modes of composites under high impact energy. The numerical results of impact force, absorbed energy, and damage morphologies on both sides for all specimens show good agreement with the experimental results.

Numerical Investigation of the Effect of Open Holes on the Impact Response of CFRP Laminates

The presence of open holes changes the behaviour of composite laminates when subjected to mechanical loads creating critical zones with a high probability of interlaminar and intralaminar damage initiation. While open holes in composite laminates are a requirement in many situations such as assembly needs, wiring, and maintenance access, their influence on the impact response of composite laminates is still poorly understood. In this paper, a numerical study was performed on Carbon Fibre Reinforced Polymer (CFRP) composite laminates with open holes subjected to low velocity impacts. The influence of the distance between open holes to impact origin, hole diameter, and the number of open holes on mechanical response and failure was studied using a FE model based on the inter-fibre failure criterion of Cuntze to account for the progressive intralaminar failure. The interlaminar failure was considered by using zero thickness cohesive elements based on the cohesive zone model. The results showed that i) open holes change the shape and size of the damage caused by low velocity impact and ii) that the presence of an open hole close to the impact origin in-plane spread of damage is stopped resulting in more severe damage and a smaller projected damage area compared to the control specimen. In addition, the presence of open holes in most cases did not change the locality of the low velocity impact but rather changed the severity of the damage in the local impact zone.

Behaviors of Composite Laminates Under Low-Energy Impact Using a Novel Analytical Framework

Carbon fiber-reinforced polymer (CFRP) composite laminates have the characteristics of orthogonal anisotropy and heterogeneity, so the failure mechanism under low-energy impact is very complex. As a supplement to the experiment, it is necessary to develop numerical tools to predict the mechanical behavior of composite laminates under low-energy impact. In this paper, the mechanical behavior analysis framework of composite laminates under low-energy impact load is established by using the micromechanics of failure (MMF) theory and the mixed mode exponential cohesive zone model (CZM). The failure modes of intralaminar components in composite laminates are determined by MMF theory. The damage onset and evolution process of interlaminar delamination is described by the mixed mode exponential CZM. The finite element model of composite laminates under low-energy impact is developed using the Python scripts on ABAQUS/Explicit platform. The user-defined material subroutine VUMAT is written in Fortran language. The impact responses of composite laminates with several impact energies are predicted. The intralaminar failure modes and interlaminar delamination behavior are discussed in detail. The results show that the tensile failure of matrix and interlaminar shear delamination failure are the main failure modes of composite laminates under low-energy impact load. The experimental results present better consistency with the numerical analysis, indicating that the constructed multiscale analysis method is efficient and accurate. This study expands the analysis method of mechanical behavior of composite laminates under low-energy impact. The constructed mixed mode exponential CZM also has guiding significance for the failure analysis of other bonding materials.

Effect of intra-yarn hybridisation and fibre architecture on the impact response of composite laminates: Experimental and numerical analysis

Advanced composite laminates (i.e. glass composite laminates) are highly susceptible to low velocity impact, and the induced damage failures substantially reduced their residual mechanical properties and safe-service life during their application. Therefore, experiments and simulation efforts to predict their low-velocity impact damages and energy absorbing have significant importance in composite structures design. In this regards, experimental and finite element analysis (FEA) with aiding Abaqus software were respectively performed to investigate the influence of yarn hybridisation on the response of composite laminates under low velocity impact. The hybrid yarns, which consisted of S-glass and polypropylene yarns have been used to manufacture two types of composites; non-crimp cross-ply hybrid yarns and twill hybrid fabric composites. Additionally, for comparison, the non-crimp cross-ply and twill fabric composite laminates have been made from glass fibres only. The vacuum infusion resin process has been adopted to manufacture these composite laminates. The impact performance of composite laminates has been investigated using low-velocity impact at 15 J, 35, and 50 impact energy levels. The numerical analysis was executed using Abaqus/Explicit and Hashin failure criteria and continuum damage mechanics by using homogenous shell were adopted to simulate the intra-laminar damage in layers. Meanwhile, standard cohesive inter-laminar interfaces that inserted between composite layers with quadratic stress failure criteria have been used to model delamination failures. The numerical results regarding impact force-time, displacement–time and energy-time histories plots, as well as the damage evolution behaviour of matrix crack and fibre fracture, presented an agreement with experimental results.

Impact response of composite laminates based on epoxy and glass fibre

Initially, the behavior of the glass fibre reinforced epoxy (GF/Epoxy) composites under low velocity impact loading was investigated experimentally. The experimental data were then compared with the corresponding numerical results to validate a number of finite element models. Here, simulations were developed, using ABAQUS/Explicit software, to predict the response of these composite laminates under impact loading. The composite plates were modelled using Hashin failure criteria. The result showed that the developed FE models were correlated well with data obtained experimentally. The influence of parameters, i.e. impact energy, indentor diameter and impact velocity on the behavior of GF/Epoxy plates were then investigated numerically. The results have shown that the values of peak force and absorbed energy increase with the impact energy. Increasing the projectile diameter leads to increase the values of peak force, maximum displacement, duration time and perforation energy. It has also shown that the peak forces show no dependency on the impact velocity and the values of absorbed energy values show a noticed reduction as the impact velocity increases.

Experimental and Computational Analysis of Low-Velocity Impact on Carbon-, Glass- and Mixed-Fiber Composite Plates

One of the problems with composites is their weak impact damage resistance and post-impact mechanical properties. Composites are prone to delamination damage when impacted by low-speed projectiles because of the weak through-thickness strength. To combat the problem of delamination damage, composite parts are often over-designed with extra layers. However, this increases the cost, weight, and volume of the composite and, in some cases, may only provide moderate improvements to impact damage resistance. The selection of the optimal parameters for composite plates that give high impact resistance under low-velocity impact loads should consider several factors related to the properties of the materials as well as to how the composite product is manufactured. To obtain the desired impact resistance, it is essential to know the interrelationships between these parameters and the energy absorbed by the composite. Knowing which parameters affect the improvement of the composite impact resistance and which parameters give the most significant effect are the main issues in the composite industry. In this work, the impact response of composite laminates with various stacking sequences and resins was studied with the Instron 9250G drop-tower to determine the energy absorption. Three types of composites were used: carbon-fiber, glass-fiber, and mixed-fiber composite laminates. Also, these composites were characterized by different stacking sequences and resin types. The effect of several composite structural parameters on the absorbed energy of composite plates is studied. A finite element model was then used to find an optimized design with improved impact resistance based on the best attributes found from the experimental testing.

High velocity impact response of composite laminates using modified meso-scale damage models

High velocity impact response of quasi-isotropic carbon fiber reinforced polymeric laminates cured from unidirectional plies is studied using finite element models. Rigid steel spheres are used as projectiles. The intraply meso-model originally proposed by Ladevèze (LMT-Cachan) for the ply behavior based on continuum damage mechanics, is extended in this paper to take into account ply fracture energies and in-situ strengths. Constitutive modeling relies on mesh size regularization (via Bazant-type crack-band/smeared-crack formulation), orthotropic material aligned mesh and element erosion. Three different types of post-peak degradation strategies are considered and compared in the paper: (a) damage rate bound model, and smeared-crack formulation based (b) linear and (c) exponential softening laws. Models (b) and (c) are original contributions. Intraply and interply damage models are implemented via user routines in LS-Dyna, for explicit dynamic analyses. The efficiency of the novel material models to predict high velocity impact response and to mitigate the mesh size effects is studied. Predictions from the developed models are validated by comparing with test data and numerical results from the literature, and demonstrated that the two new models based on smeared-crack formulation provide accurate results.

Effect of graphene nanoplatelets on the impact response of a carbon fibre reinforced composite

In the present paper, experimental investigations were conducted to assess the effect of nanomodification on the impact behaviours of hybrid composite plates. Graphene nanoplatelets (GNPs) of two different sizes, 5 and 30 μm, were used to modify a composite material made with 64 wt.% of unidirectional fibres and a low-viscosity epoxy resin. The effect of the nanomodification with 30 μm GNPs was also studied on composite plates prepared with a higher viscosity resin. Three laminate thicknesses (4, 8, and 16 layers) were tested with a standard drop dart testing technique. The peak forces as well as the absorbed energy and the fracture surfaces, observed with a Scanning Electron Microscope (SEM), were compared. Experimental results showed that nano-modification with 5 μm particles had a detrimental effect on both the peak forces and the absorbed energy, whereas the addition of 30 μm GNPs increased the absorbed energy, especially for a laminate thickness of 16 layers. Overall, the experimental results demonstrated that the size of graphene nanoparticles has a significant effect on the impact response of composite laminates.

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.

Research on intralaminar load reversal damage modeling for predicting composite laminates’ low velocity impact responses

Despite abundant finite element analysis (FEA) of low velocity impact (LVI) performance of composite laminates, the questions regarding the effects of different load reversal damage laws on predicted impact responses of composite laminates and which one is preferred for more physically-sound simulation of laminate LVI responses remain unresolved. In this paper, an elasto-plastic progressive damage model based on three load reversal damage laws including coupled tension-compression law, semi-stiffness recovery law and full-stiffness recovery law, were numerically implemented in predicting laminate LVI responses. By comparisons between simulations and available experimental data, the influences of different load reversal damage laws on predicted delamination threshold load, impact force, laminate central deformation, dissipated impact energy as well as damage status were analyzed. More accurately predicting laminates’ LVI responses, the semi-stiffness recovery law was concluded as the preferred intralaminar load reversal damage law.

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.

Experimental study of temperature effects on composite laminates subjected to multi-impacts

Abstract Literature reports several works about the effect of temperature on the impact response of composite laminates, but very few studies can be found in terms of multi-impacts performance. Therefore, a systematic study reveals to be necessary. For this purpose, Glass Fibre Reinforced Composites (GFRP) subjected to single and multi-impact events with the same total energy (1 J and 3 J) were analysed. Experimental tests were performed using a drop weight-testing machine and three different temperatures (room temperature, 60 °C and 90 °C) were selected taking account the Tg of the resin. It was verified that the temperature has negligible influence for higher impact energies, while a strong effect occurs for lower energies. Finally, the number of impacts to failure is very dependent of the temperature, which is explained by its influence on the global properties of the matrix.

Micro–macro FE modeling of damage evolution in laminated composite plates subjected to low velocity impact

A phenomenological-based micro–macro mechanical method, comprising the coupling of a 3D continuum damage mechanics (CDM) model with an original micromechanical FE model, is presented to predict low velocity impact response of composite laminates. The key point of the proposed method is the definition and computation of saturation crack density, which is used to scale impact-induced delamination instead of via expensive cohesive zone model based FEM. In order to gain the specific value of the saturation crack density, a micromechanical FE model is established based on the RVE technique. Additionally, the initiation of intralaminar failure including fiber fracture (FF) and inter-fiber fracture (IFF) is evaluated by Puck criteria, and its evolution, with considering effects of the fracture plane angle, is assumed to be controlled by equivalent strains on the fracture plane rather than the classic material principal axis plane. A good agreement between the experimental and simulated results shows correctness and effectiveness of the developed micro–macro mechanical method for predicting impact response and damage using a relatively coarse mesh. Furthermore, significant reduction of computational cost, compared with existing techniques, can be achieved with the novel mesh-independent method.

Comparison of the effect of preload and curvature of composite laminate under impact loading

In this paper, the effect of preload on impact response of composite laminates is considered. To this aim, three specimens were manufactured and tested under 4 different impact conditions: 1- A curved laminate without preload. 2- A preloaded curved laminate, showing a lower radius of curvature due to the preload. 3- A curved laminate without preload but initial reduced curvature. The particular test conditions studied here allow estimating and discerning the effect of pre-stress and curvature on the impact response. Results show that the preload leads to an increased curvature, to which it follows that the maximum impact force and the damaged area increase significantly. The comparison of the impact response of the second and the third specimens show that, in the case of similar curvature, the preload leads to a lower damaged area. These results are particularly important for designing of curved composite components.

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.

Finite element simulation of carbon fibre-reinforced composite laminates subjected to low velocity impact using damage induced static load-deflection methodology

This work is concerned with the prediction of low velocity impact damage resistance of carbon fibre-reinforced laminated composite laminates. Pre-assumed damage induced laminates were simulated to correlate damage corresponding to impactor nose profiles. Majority of the existing studies conducted on the topic are experimental, based on three-dimensional stresses and failure theories that cannot readily predict ply level impact damage. Hence efficient computational models are required. The present study was conducted to efficiently predict ply level impact response of composite laminates. Static load-deflection based computational model was developed in the commercial software ABAQUSTM. Eight, 16, and 24 ply laminates impacted by point, small, medium, and flat nose impactors were considered with emphasis on flat nose impacts. Loading areas under the impactor nose profiles were partitioned to investigate effects from variations in applied loading. Pre-assumed damage zones consisting of degraded material properties equivalent to the impactor nose profiles were inserted across thickness of the laminates to predict ply-by-ply damage. Impactor nose profiles and pre-assumed damage zones (size, type, and location) were correlated to the simulation produced deflection quantities to predict the ply level damage. Selected results were compared against the data available in the literature and also against the intra-simulation results and found in good agreement.

Low-velocity impact response of composite laminates with steel and elastomer protective layer

In the presented study the response of a carbon-glass composite/steel/(elastomer) multi-material structure to low-velocity impact was investigated experimentally. Two different steel layer thicknesses, 0.125mm and 0.25mm, as well as the addition of a rubber layer were assessed regarding their influence on internal and external damage, the absorbed energy, force evolution, and deformation.It was found that the doubling of the steel layer thickness stiffens the structure marginally and induces deeper indentations but has no significant influence on the absorbed energy or the damage threshold FD. The additional rubber layer increases the damage threshold load. Below this threshold, the response is dominated by global, elastic deformation decreasing internal and external damage and thereby the amount of absorbed energy. Above FD, large local deformations around the centre of impact lead to a more critical surface damage which dissipate a part of the energy decreasing the extend of delaminations.