Low Velocity Impact Research Articles

Low-velocity impact analysis and multi-objective optimization of hybrid carbon/basalt fibre reinforced composite laminate

Three-dimensional in-plane progressive damage model was developed for carbon/basalt fibre interlayer hybrid composites in this study, and cohesive element model was employed to simulate interlaminar damage. Numerical simulation of low-velocity progressive impact damage of hybrid composite laminate was carried out, and its accuracy was verified by physical impact test, with the maximum error of the maximum contact force, maximum displacement and energy absorption not exceeding 6.1% and the maximum error in damage area size within 4.8%. The effects of lay-up structure and angle on the impact properties of hybrid laminate were investigated through simulation. Finally, real number coding strategy was proposed for the parametric representation of the lay-up material and angle of each layer. Multi-objective optimization of hybrid laminate based on Kriging surrogate model and hybrid algorithm composed of elitist non-dominated sorting genetic (NSGA2) algorithm and multi-objective particle swarm (MPSO) algorithm was conducted. The optimal trade-off solution was selected from the Pareto solutions using technique for ordering preferences by similarity to ideal solution (TOPSIS) coupled with principal component analysis (PCA) methods. The coefficient of variance between peak force and maximum displacement of the optimized laminate was 49.3%, 44.9% and 31.4% lower than those of the pure CFRP laminate, pure BFRP laminate, and hybrid laminate before optimization, respectively, indicating that the balance degree of impact displacement and force has been substantially improved. The progressive impact damage simulation and parametric optimization design methodology proposed in this study provide useful guidance for the design of hybrid composite laminate.

Low-velocity impact responses and failure of sandwich structure with carbon fiber composite honeycomb cores

The objective of this study is to examine the response and failure of honeycomb sandwich structures made of carbon fiber reinforced polymer (CFRP) composites under low-velocity impacts. Four impact tests with varying energies are performed to induce four distinct damage states in the sandwich structure: no discernible damage, damage to the top face sheet and a portion of the core, damage to the lower face sheet, and total penetration. The damage characteristics of the sandwich structures is analyzed by using industrial tomography technology (CT) without destroying them. A refined finite element model is established to further explain the deformation behavior and energy absorption mechanism of the structure, clarifying the effects of the honeycomb core's structural parameters, such as wall thickness, cell side length, and core height. To enhance the precision of simulation outcomes, a model for the onset and progression of damage in plain woven composites is incorporated into the user-defined material subroutine. The experiments and simulations demonstrate a high level of consistency in terms of peak loads, failure mode, and energy absorption.

Aluminum hierarchical tubular structure inspired by skeletal muscle tissues: Quasi-static and low-velocity impact testing

This paper investigates experimentally and numerically the protective capability of skeletal muscle-inspired hierarchical tubular (MHT) structures made of aluminum under both quasi-static and dynamic impact conditions. In the quasi-static compression tests, structures with higher hierarchical order were more deformable and had lower contact force. Dynamic impact tests were conducted for the first time on MHT specimens of three different hierarchical orders using a drop tower facility. The results indicated a significant reduction in both the maximum and mean contact forces on the protected body when shielded by the second- and third-order MHT structures. This suggested that increasing the hierarchical order of the structure effectively enhanced impact protection capability. Numerical models were developed using ABAQUS/Explicit to accurately reproduce the deformation process and force-time functions of the dynamic impact scenarios. A parametric study found that the impact resistance performance of the MHT structures was robust against various impact velocities and masses.

Numerical simulation of the damage and ignition responses of high explosives under low-velocity impact using the SPH method

The damage evolution and ignition mechanism of high explosives are of great importance in assessing the safety of munitions and guiding the design of munitions. In this study, the smoothed particle hydrodynamics (SPH) method is combined with a viscoelastic–viscoplastic-damage constitutive model and a hot spot model to explore the damage and ignition responses of high explosives under low-velocity impact. In particular, the sub-particle method is developed in the SPH method to combine the macroscopic constitutive model with the mesoscopic hot spot model. First, the damage evolution of a compressed plate containing a cavity and the ignition response of a single particle at a given pressure and strain rate are studied separately, and the simulation results are validated by experimental results and existing finite element method simulations. Subsequently, the impact shear and crack extrusion tests of high explosives with complex stress states are explored, respectively. For typical pressed PBX under impact-shear loading, a large damage region is formed in the high explosives due to the tensile stress formed by the meeting of rarefaction waves, and the initial ignition region is mainly located in the region where the outer edge of the rod is in contact with the high explosives and extends in a circular shape to the inside of the explosives. For typical pressed PBX under crack extruded loading, the damage region is mainly concentrated in the materials squeezed into the crack, and the initial ignition region is mainly located around the crack and gradually extends above the crack. The results indicate that the proposed SPH method is capable of modeling the damage and ignition responses of high explosives under complex stress states.

Multiscale damage and low-velocity impact study of three-dimensional woven composites

Three-dimensional woven composites address the limitation of weak interlaminar strength found in traditional laminated composites and offer superior resistance to out-of-plane impact. However, the complex material composition and structural intricacies necessitate investigation into their damage mechanisms. This study introduces novel and reliable microscale and mesoscale Representative Volume Element (RVE) models for three-dimensional woven composites, developed through advanced CT scanning and comprehensive multi-directional tensile and shear experiments. The research explores the impact of fiber volume fraction on yarn mechanical properties using the microscale RVE model, yielding precise macroscale homogenization parameters through the mesoscale RVE model. Furthermore, a macro-meso model tailored for low-velocity impact scenarios is established, significantly enhancing computational efficiency without compromising accuracy, thus providing support for further research on the impact properties of three-dimensional woven composites.

Experimental investigation of the effect of fabric wrapping method and autoclave curing on the mechanical and thermal degradation of carbon nanotube doped and undoped carbon composite pipes

AbstractAlthough it is seen in the literature that composite pipes are produced by filament winding, there are limited number of studies on the use of fabric wrapping and autoclave. In this study, in order to fill this gap and contribute to the literature and industry, composite pipes were produced using fabric wrapping and autoclave methods together and their mechanical and thermal properties were investigated. The effect of carbon nanotube (CNT) reinforcement on these properties was also investigated. According to low velocity impact (LVI) test, 10%–25% impact strength increase was observed with CNT reinforcement. Thermogravimetric analysis (TGA) shows that mass loss decreased by ⁓10% and the degree of thermal degradation increased by ⁓10%. In dynamic mechanical analysis (DMA), it is observed that epoxy glass transition temperature (Tg) increased by 11% with CNT reinforcement. At the end of the study, the mechanical and thermal properties of the pipes produced by autoclave and fabric wrapping methods were improved compared to the literature and contributed to science and therefore to the increased use of prepreg carbon pipes in the industry.Highlights Composite carbon pipes were produced by applying prepreg fabric wrapping and autoclave curing methods together. The mechanical and thermal properties of multi‐walled carbon nanotube (MWCNT) reinforced and unreinforced carbon composite pipes were investigated. According to TGA, it was observed that the mass loss decreased. Thermal decomposition temperature increased for MWCNT reinforced and unreinforced samples. According to DMA, Tg of epoxy decreased for MWCNT unreinforced sample and increased for MWCNT reinforced sample.

Fabrication and mechanical properties of a high-performance PEEK-PEI hybrid multilayered thermoplastic matrix composite reinforced with carbon fiber

This paper presents a method for manufacturing a hybrid matrix composite material reinforced with a woven carbon fiber that combines the properties of two thermoplastic polymers: PEEK (polyether-ether-ketone) and PEI (polyether-imide). The manufacturing process involves a multilayer architecture and a single hot-pressing consolidation step. Experimental tests — including uniaxial tensile tests, delamination tests in Mode I and impact tests at low velocities — were conducted to compare the resulting laminate with single matrix materials (PEEK/CF and PEI/CF).The improvements in strain to failure by 48 % in tensile tests with fiber orientation at ±45∘ and in delamination force by 13 % in low velocity impact tests with respect to PEI/CF show that the heterogeneous matrix blend maintains the crystalline content and excellent elastoplastic response of PEEK while taking advantage of the affordability, lower processing temperature and toughness of PEI.

The mechanical properties of Kevlar three-dimensional angle-interlock fabrics and composites

In this article, in order to investigate the difference of mechanical properties between three-dimensional angle-interlock (3DAI) structure and two-dimensional (2D) structure. Kevlar filaments were used as raw material to prepare 3DAI fabrics. The tensile properties of Kevlar 3DAI fabrics were investigated and the influence of warp damage and crimp wave height on the tensile properties was analyzed too. The bending properties and low-velocity impact properties of the 3DAI Kevlar/EP composites and the 2D composites were compared. The results revealed that the warp degradation and crimp percentage in 3DAI fabrics increase with the increase of weft density. The maximum warp degradation rate is 15% and the maximum crimp percentage is 5.4%, which has a negative effect on the mechanical properties of the 3DAI fabrics and the developed Kevlar/EP composites. Compared with the 2D plain composites, the 3DAI composites have superior impact resistance and anti-stratification performance. Moreover, which also has a superior ability to withstand multiple impacts.

Effects of impact angles and shapes on CAI strength of composite honeycomb structure

The Compression After Impact (CAI) strength can enhance safety and reliability in engineering applications, improve simulation and prediction capabilities. It is also an important indicator for assessing the damage tolerance capacity of composite structures. The CAI strength is directly influenced by low-velocity impact, which holds significant scientific research implications for evaluating structural safety, optimising design and enhancing material properties. Analysing different impact shapes and angles provide a closer representation of real-world engineering scenarios, rendering results more reliable and valuable. The subject is a CFRP panel with Nomex honeycomb sandwich structure, where both the skin and core are composed of composite materials. Low-velocity impact and compression after impact tests were conducted to establish an integrated and refined finite element model for the CFRP panel with Nomex honeycomb structure. The model’s validity was confirmed by comparing with test results. Various impact shapes and angles were investigated using the established model to examine their influence on the CAI strength of the composite honeycomb sandwich structure. The following conclusions were drawn: (1) Sharper impactors result in lower CAI strength and higher compressive failure displacement. (2) The CAI strength, normalised CAI strength, and failure displacement of the structure increase with the impact angles. Among the tested angles, the 30° impact angle induced the least damage, exhibiting the highest CAI strength, normalised CAI strength, and failure displacement. However, as the angle increases, energy losses between the impactor and specimen increase, impact energy decrease. Consequently, the structural indicators decrease compared to the 30° impact angle.

Drop-weight impact and compressive properties of repeatable self-healing carbon fiber reinforced composites

Herein, repeated self-healing of impact damage in carbon fiber reinforced composites is successfully achieved by using hollow glass fibers containing self-healing resin and two types of microcapsules (HGFs-Ms). The HGFs-Ms and microcapsules containing hardener were incorporated to fabricate repeatable self-healing carbon fiber reinforced polymer composite laminates (RSH-CFRPs). Low-velocity drop-weight impact tests and compression tests were performed to investigate the impact resistance, energy absorption, residual compressive strength and repeated self-healing performances of the RSH-CFRPs. The results revealed that the energy absorption capacity of the RSH-CFRPs could be repeatedly recovered and the barely visible impact damage (BVID) zone was almost fully healed after every healing process. Moreover, the RSH-CFRPs successfully minimized the reduction in compressive strength after repeated drop-weight impact tests due to their efficient repeated self-healing ability in impact induced damage.

Linear Contact Load Law of an Elastic–Perfectly Plastic Half-Space vs. Sphere under Low Velocity Impact

The impact of contact between two elastic–plastic bodies is highly complex, with no established theoretical contact model currently available. This study investigates the problem of an elastic–plastic sphere impacting an elastic–plastic half-space at low speed and low energy using the finite element method (FEM). Existing linear contact loading laws exhibit significant discrepancies as they fail to consider the impact of elasticity and yield strength on the elastic–plastic sphere. To address this limitation, a novel linear contact loading law is proposed in this research, which utilizes the concept of equivalent contact stiffness rather than the conventional linear contact stiffness. The theoretical expressions of this new linear contact loading law are derived through FEM simulations of 150 sphere and half-space impact cases. The segmental linear characteristics of the equivalent contact stiffness are identified and fitted to establish the segmental expressions of the equivalent contact stiffness. The new linear contact loading law is dependent on various factors, including the yield strain of the half-space, the ratio of elastic moduli between the half-space and sphere, and the ratio of yield strengths between the half-space and sphere. The accuracy of the proposed linear contact loading law is validated through extensive Finite Element Method simulations, which involve an elastic–plastic half-space being struck by elastic–plastic spheres with varying impact energies, sizes, and material combinations.

Numerical modeling of flax-woven reinforced composites submitted to quasi-static indentation and low velocity impact

Numerical modeling of flax-woven reinforced composites submitted to quasi-static indentation and low velocity impact

Inter-layer failure and toughening mechanisms of carbon/aramid hybrid fiber composites interleaved with micro/nano pulps under low-velocity impact load

Hybrid fiber-reinforced polymer (HFRP) composites are widely used in aerospace structures because of their excellent overall performance. However, it is still challenging to address the issue of high sensitivity to delamination between dissimilar material interlayers in HFRP composites. This study combines experimental and numerical simulation to analyze the low-velocity impact behavior and interlaminar damage of two types of HFRP. Based on a micromechanical model, an equivalent aramid pulp (eAP) toughening laminate model is developed. The impact behavior of the HFRP toughen by eAP only in dissimilar material interlayers is simulated based on the model. The effect of eAP areal density on the impact behavior and evolution of interlaminar damage is analyzed. Results show that the maximum force and impact stiffness of eAP-toughened HFRP increase initially with the increase in eAP areal density, and then decrease slowly. The area and extent of damage of dissimilar material interlayers in eAP toughened laminates is significantly reduced. Finally, the interlaminar toughening and failure mechanisms by eAP-toughening only in dissimilar material interlayers of the HFRP composites are systematically revealed from fiber bridging and damage transfer perspectives.

Dynamic behaviors of seismic-designed RC beams under asymmetrical low-velocity impact loads

Seismic-designed reinforced concrete (RC) structures could be subjected to asymmetrical low-velocity impact loads, e.g., vehicle/barge collisions and rockfall impacts, while existing studies mainly focus on the dynamic responses of symmetrical impacted scenarios. This study experimentally and numerically examined the influence of stirrup ratio and impact location on failure modes and impact behaviors of RC beams. Firstly, symmetrical and asymmetrical drop-weight tests were conducted on six RC beams, and digital image correlation technique was applied to capture the damage evolution process and dynamic responses. Then, the above test was reproduced to validate the applicability of the finite element analyses approach, and numerical simulations were further performed to explore the transformation mechanism of the failure mode of asymmetrical impacted beams. The results showed that, (i) the shear-bending capacity ratio of the beam decreased with the stirrup ratio increasing or the impact location moving towards the mid-span, causing its failure mode to transform from shear to flexural under asymmetrical impact loads; (ii) the shear bearing capacity mainly controlled the occurrence of concrete cracking of asymmetrical impacted beams, and moment bending capacity influenced the post-cracked performance; (iii) increasing the stirrup ratio improved the joint action between longitudinal bars and stirrups and enhance the confinement effect on concrete, reducing the damage degree and deformation of asymmetrical impacted beam; (iv) under the effect of shear wave propagation, asymmetrical impacted beams completed the global impact process faster than symmetrical impacted ones. Finally, a two-degree-of freedom model was established to quickly calculate the displacement-time history at the impact location of asymmetrical impacted beams. The current work could provide a helpful reference for the impact-resistant design of RC structures against asymmetrical impact loads.

A plate containing a central rectangular hole made of PMMA resin and reinforced with graphene particles: low-velocity impact analysis

Purpose Due to the important and extensive use of graphene in the engineering structures, the purpose of this paper is to investigate the low-velocity impact (LVI) response of a graphene-reinforced plate with a rectangular central hole. Design/methodology/approach In this paper, Halpin-Tsai theory is used to model the mechanical properties of the plate made of polymethyl methacrylate (PMMA) resin and graphene particles. First, the plate displacement field is presented, and then the strains and stresses are obtained. The motion equations are extracted using energy equations, Ritz method and generalized Lagrange equations. The verification of theoretical formulation shall be carried out using the ABAQUS finite element software suite. Findings The effects of graphene volume fraction, approaching the impact point to the corner of the rectangular plate, and different boundary conditions of the plate are studied for LVI of impactor with spherical tip on the rectangular central hole reinforced by graphene. Important responses of the impact, such as the contact force between the impactor and the plate as well as the displacement of the plate at the impact place, are investigated and analyzed in this research. Originality/value Considering the wide application of graphene in the engineering structures, the simulation of the LVI on the graphene-reinforced plate made of PMMA resin with a rectangular central hole is carried out in this paper using numerical and theoretical modeling.

Mechanical strength and low-velocity impact behavior of glass fiber reinforced filament wound pipes with different number of layers after hydrothermal aging

Composite pipe is preferred over metal and other materials for water supply, liquid chemical transport, and fuel and gas transport. This is because composite pipes are more corrosion resistant, have a high strength/density ratio, high stiffness/density ratio, and more durable than metal pipes. The properties of the composite pipes employed may differ based on the operating environment. Therefore, determining the properties of the composite pipe according to the working environment is extremely important for its lifespan. The thickness of the samples is increased in line with different needs (such as increased strength). Increasing the thickness of samples, especially those exposed to different environmental conditions, and investigating the changes that will occur in the physical and mechanical properties of the samples are another important situation. In this investigation, glass fiber (GFRP) reinforced epoxy composite pipes have been examined, which were manufactured using the filament winding method with different layers [±55°]. To determine their properties in different working environments, the GFRP composite pipes were subjected to hydrothermal aging in pure water at 80°C for several days (7, 14, 21, and 28). The changes in their mechanical properties under working conditions were determined through hoop tensile strength tests and low velocity impact tests applied at different energy levels. The experimental results show that the tangential stress values increased by 10.59% as the number of layers increased. As the aging time increased, the durability of the 6-layer composite pipe decreased by 17.69%. Furthermore, the ability of the aged pipes to withstand damage was evaluated, revealing that the aging process exacerbated the damage within the pipes.

Quasi-static uniaxial compression and low-velocity impact properties of composite auxetic CorTube structure

Auxetic structures are gaining great attention due to their unique contraction deformation characteristics under compression and impact. In this paper, high performance carbon fiber-reinforced composites are used to fabricate the auxetic structure consist of corrugated sheets and tubes (CorTube). The quasi-static uniaxial compression and low-velocity impact properties of composite CorTube structure are explored. The response of the composite CorTube structures under quasi-static compression loads are analyze through a combination of theoretical analysis, simulations, and experimental tests. Additionally, drop-weight impact tests are conducted using a rigid impactor with a hemispherical head to examine the effects of impact energy levels, impact locations, and corrugated sheet thickness on the impact response of CorTube structure. Enhancing corrugated sheet-tube bonding via modified cross members and reducing tube crushing during quasi-static compression are notable findings. The results also highlight the remarkable auxetic properties of the composite CorTube under low-speed impact, and the impact resistance could be enhanced by increasing the corrugated sheet thickness and stiffness. Various failure modes were observed, including cracks, pits, tube crushing, and delamination. Significantly, peak-impacted specimens exhibited greater maximum displacement with lower peak impact forces. This study offers insights into the deformation and failure modes of auxetic CorTube structures under low-velocity impact.

Damage classification and evolution in composite under low-velocity impact using acoustic emission, machine learning and wavelet packet decomposition

The primary objective of this research is to conduct an exhaustive experimental investigation into the damage identification and damage evolutionary mechanisms in laminated CFRP under low-velocity impact. The recorded acoustic signals were classified by Principal Component Analysis, Pearson correlation analysis and K-means++ clustering algorithm and four damage modes including matrix cracking, delamination, fiber–matrix debonding and fiber failure are identified. The Wavelet Packet Decomposition is used to analyze the characteristics of the signal in the time–frequency domain. Matrix cracking is the fundamental damage mode, with its characteristic frequency band being FB1. An increase in the FB3 of matrix cracking signals indicates the tendency to the inter-laminar region, leading to delamination damage. Fiber-matrix debonding is a two-phase damage mode. The transition of the energy components from FB1 to FB7, as indicated by the scanning electron microscopy (SEM) results, signifies the evolution of Fiber-matrix debonding. The initial stage is dominated by matrix peeling off the fiber surface, while the second half of the loading shows matrix peeling accompanied by fiber fracture. Fiber breakage failure is caused by local stress concentrations due to matrix cracking. In the later stages of loading, fibers fail by brittle fracture due to mutual compression without the involvement of matrix cracking as reflected by SEM and WPD.

Response of the orthogonal corrugated sandwich panel under low-velocity impact with different shaped impactors

This study aims at investigating the low-velocity impact resistance of the composite orthogonal corrugated sandwich panel through experimental and simulation methods, considering different shaped impactors. To that scope, the progressive damage model with the sandwich panel is developed and numerical investigations are carried out in ABAQUS / Explicit. The results show that as the impactor changes from flat to hemispherical and then to conical shape, the first peak load gradually decreases, and the maximum displacement of the impactor and total energy absorption gradually increase. The high impact energy makes the sandwich panel more compliant. Furthermore, the expansion area of fiber damage, matrix damage and delamination in the top face sheet, core and bottom face sheet depends on the impactor shape and impact energy. Under high impact energy, the damage under the conical impactor mainly expands along the thickness direction of the sandwich panel rather than in the in-plane direction, while the flat impactor causes large damage area in the in-plane direction as well.

Effect of Oblique and Off-Center Impact on CFRP Laminate Under Low Velocity Impact

Effect of Oblique and Off-Center Impact on CFRP Laminate Under Low Velocity Impact