Low Velocity Impact Behavior Research Articles

A comparative study on the low velocity impact behavior of UD, woven, and hybrid UD/woven FRP composite laminates

This study is aimed at comparing the response and damage of unidirectional (UD), woven fabric (WF) and hybrid UD/WF fiber reinforced polymer (FRP) laminates subjected to low velocity impact. The unidirectional tape and/or woven fabric (plain weave) carbon/epoxy prepregs are laminated and hot-pressed to produce UD, WF and sandwich-like hybrid UD/WF specimens. Impact responses of specimens are determined through low velocity impact (LVI) tests with impact energies of 10 J, 17 J and 25 J. After the LVI tests, the damage of specimens is characterized and analyzed using a combination of visual inspection, ultrasonic phased-array inspection, micro-computed tomography (CT) inspection, cross-sectional microscopic observation, and thermal de-ply test. Also, the LVI damage mechanisms of the three types of specimens are quantitatively compared by using the inter fiber crack volume ratio, total delamination area and fiber fracture length. It is concluded that the fiber architecture plays an important role in determining low velocity impact behavior of composite laminates. Especially, for the sandwich-like hybrid UD/WF laminates whose surface is a WF layer and the core is a UD layer, the WF layer on the surface plays an important role in reducing matrix cracking, delamination and fiber fracture, thus improving its LVI resistance.

Experimental investigation on low-velocity impact behavior of glass, Kevlar, and hybrid composites with an elastomeric polyurethane matrix

Low-velocity impacts represent a critical dynamic condition for engineering structures. Combining two reinforcing fibers in a single matrix, i.e., hybridization, is considered a feasible way to improve composite performance. In this context, this paper presents an experimental work on composites with Kevlar and glass fabrics and a novel thermoset polyurethane matrix. The coupons are manufactured by vacuum infusion technique and low-velocity impact tests are carried out. First, the impact behavior of Kevlar and glass laminates of different thicknesses is assessed, and then impact tests are performed on different configurations of hybrid laminates, both symmetric and non-symmetric. For the non-symmetric specimens, impact tests were conducted on both sides of the stack. Load vs displacement curves are reported along with absorbed energy. To investigate the damage mechanism, the front, back, and cross-section views of the specimens are analyzed, and features related to the stacking sequences are discussed. Thermographic analyses are carried out on the impacted specimens to further analyze damage. The failure mechanisms are different from traditional epoxy composites and a hybridization effect is reported. The results evidence that the hybrid coupons are viable for structural applications, being capable of absorbing high-impact energies, in particular, non-symmetric hybrid laminates outperformed the Kevlar, glass, and symmetric ones, absorbing roughly 15% less energy for the highest energy impact.

Investigation of low-velocity impact behavior of two-way RC slab strengthening with basalt TRM strips

Investigation of low-velocity impact behavior of two-way RC slab strengthening with basalt TRM strips

A new integrated modeling method for predicting low-velocity impact behavior and residual tensile failure of Z-pinned T-joints

Composite T-joints are highly susceptible to low-velocity impact, which can significantly affect their residual performance due to the primary working condition of bearing out-of-plane tensile loads. Currently, most methods that employ multiple models or analytical steps to sequentially assess the mechanical properties of composites generally exhibit certain limitations, leaving room for improvement. This study has developed a finite element (FE) model to simulate the low-velocity impact and post-impact tensile behaviors of carbon fiber reinforced polymers (CFRP) T-joints using an integrated analysis method. The model is based on stress failure criteria and continuous stiffness degradation theory and incorporates corrections to the damage variables. Both the low-velocity impact and quasi-static tensile portions of the model are implemented using an explicit solver with the VUMAT subroutine for calculations in Abaqus. The element damage states are transferred between the two models via a Python script, mitigating the inefficiencies and uncontrollable errors associated with the traditional method of transferring element information between multiple models or analytical steps. Finally, the numerical results of mechanical response and damage states are compared with experimental findings from various perspectives, and the bridging mechanism of Z-pins is thoroughly investigated. The results show that the model exhibits a maximum error of 10.41 % in the main key parameters during low-velocity impact and a maximum error of 10.30 % in the ultimate load during post-impact tension. The model's delamination damage state and final tensile failure mode closely align with the experimental results. Furthermore, a comprehensive analysis of the FE model indicates that the pull-out force of the Z-pin is unrelated to its implantation position or pull-out rate, and the reinforcing effect of the Z-pin becomes significantly apparent only after the CFRP T-joint reaches a certain degree of initial damage.

Experimental and Numerical Study on the Low Velocity Impact Behavior of ABR Pipe

The low velocity impact load on pipes during transportation, construction and operation will cause pipeline damage and lay hidden dangers for the safety of pipeline engineering. To study the low velocity impact performance of pipes made of acrylate polymer blended with polyvinyl chloride resin for water supply (ABR), 20 sets of specimens with different heights and different masses of drop hammer were carried out to study the mechanical properties of ABR pipes. Based on the impact time curve, the energy dissipation capacity and impact peak value of ABR pipe specimens were analyzed, and the empirical calculation formula of impact force peak based on the test data is obtained by the dimensional analysis method, with a relative error ranging from −7.8% to 4.1%. Moreover, the finite element numerical simulation of ABR pipe specimens subjected to impact load is carried out, and the strain development law and failure mode of the pipe under low-speed impact load are analyzed. Therefore, the calculation formula of peak impact force and failure mode proposed in this paper can provide safety assessment methods for pipeline engineering designers and constructors.

Low-velocity impact behaviors of sandwich composites with different structural configurations of foam core: numerical study and experimental validation

Sandwich composites have very weak properties as well as superior properties. Damages will be invisible and may create huge problems due to the high strength difference of composite components. To investigate sandwich composites, numerical studies’ importance is so high because experimental studies require high labor and are time-consuming. In this study, low-velocity impact properties of the configurations of sandwich composites with E-glass fiber/epoxy and PVC foam core are investigated numerically, and the results are compared with experimental results. Reference sandwich composite, and four different types of configurations are modeled with homogenized properties. Numerical simulations are performed using the material models of rigid impactor, foam core, and composite material models of LS-DYNA software. Numerical and experimental results of these sandwich composites are compared in terms of contact force-time and contact force-displacement curves, core/facesheet debonding areas, peak contact forces, absorbed energy, maximum displacement, and contact time; a good agreement is obtained.

Low-velocity impact and compression after impact behaviour of nanoparticles modified polymer composites

Optimizing the impact properties of polymer composites is essential in aircraft industries. Hybridization of fibres is one of the efficient methods to enhance the impact properties of polymer composites. Dispersion of nanoparticles into epoxy resin improves the toughness of composites. This study examines the low-velocity impact (LVI) behaviour of hybrid epoxy-based carbon/glass fibre-reinforced laminates. Initially, the epoxy resin was modified with 0, 0.5, 1, 1.5, and 2 wt% of nanoclay and TiO2 nanoparticles using mechanical stirring followed by an ultrasonication method. To investigate the influence of stacking sequences, laminates were fabricated with (90 G/0 G/90 C)S, (90 G/0 C/90 G)S, and (90 C/0 G/90 G)S. The samples used for this study are six-ply symmetric laminates. Laminates were impacted with different impact energies between 30 and 80 J with an impact velocity of 7 m/s to generate damages. The residual strength of damaged specimens is determined using compression after the impact test. The order of stacking, fibre orientation, and the presence of nanoparticles all have a significant impact on the residual strength of laminates. By using C-scan images, layer-wise damage mechanisms were identified. The specimen with (90 C/0 G/90 G)S sequence has very high damage resistance compared to other laminates.

Low velocity impact behaviors and highly residual compressive strength of epoxy foam‐filled 3D woven composites

AbstractIn this work, a new type of epoxy foam‐filled 3D woven spacer composites (FF‐3DWSCs) was designed and manufactured by self‐made 3D loom and foaming technology. The low velocity impact behaviors, residual compressive properties and strengthening mechanisms of epoxy foam were systemically investigated. As the results, the FF‐3DWSCs showed higher impact load of 4000–5200 N than that of 3D woven spacer composites (3DWSCs) (2800–4300 N) at the energy from 10 to 40 J. The residual compressive strength of FF‐3DWSCs (23.85 MPa) was maintained at about 80% after 30 J energy impact. Due to the good compatibility of the epoxy foam and the epoxy resin and the synergistic effect between the pile yarn and the epoxy foam, the interface between epoxy foam and fiber/epoxy was strong. Therefore, the novel FF‐3DWSCs proposed here exhibited excellent impact properties and energy absorption capacity and can be used as a candidate material in the field of high‐performance composites.

Determination of Energy Absorption Capabilities of Shear Thickening Fluid Impregnated Aramid Fiber Fabrics for Ballistic Applications

Low velocity impact behavior of shear thickening fluid (STF) impregnated aramid fabric having different number of layers had been investigating throughout this study to determine a relationship between number of layers and perforation energy. Firstly, STF solutions including polyethylene glycol, silica nanoparticles and ethanol were prepared by mixing a homogenizer. Solutions containing 20% silica nanoparticles by weight were used in this study. Rheological analysis was performed to observe thickening behavior of solution. After thickening behavior and critical shear rate was determined from rheological analysis, solution was impregnated into aramid fabric. Then, specimens having different number of layers from 1 to 8 were prepared for low velocity impact experiments. A drop weight impact test was applied at different energy levels and perforation energy was determined. Finally, a curve fitting equation was found to use it for potential energy absorption applications such as ballistic impact.

Quasi-Static and Low-Velocity Impact Behavior of Injection Over-Molded Short/Continuous Fiber Reinforced Polypropylene Composites

Quasi-Static and Low-Velocity Impact Behavior of Injection Over-Molded Short/Continuous Fiber Reinforced Polypropylene Composites

Localization of surface dent deformation and inter-laminated damage in CFRP laminates under low-velocity impact behavior based on multi-channel one-dimensional convolutional gated recurrent unit

Lamb wave has become one of the most promising methods for carbon fiber-reinforced plastics (CFRP) damage detection. However, the wave velocity difference caused by CFRP anisotropy makes the time information-based localization methods lack accuracy. Obtaining high resolution and accuracy with limited excitations and sensors is difficult, which leads to difficulties in localizing small-size impact damage. Therefore, this paper proposed multi-channel one-dimensional convolutional gated recurrent unit (MC1-DCGRU) for surface dent deformation and inter-laminated damage caused by low-velocity impact behavior localization combining the feature extraction capability of the multi-channel one-dimensional convolutional neural network (MC1-DCNN) and the temporal information capturing ability of gated recurrent unit (GRU). The localization mean Euclidean distance (MED) of single-point and two-point cumulative damage is 4.29 mm and 5.78 mm, respectively. The proposed method overcomes high-resolution requirements for damage localization. It achieves higher accuracy without increasing excitations and sensors, which also achieves multi-point cumulative damage localization.

The effect of various shape core materials by FDM on low velocity impact behavior of a sandwich composite plate

In this research, the effect of various shape core materials by FDM on low velocity impact behavior of a sandwich composite plate is investigated. According to ASTM standards, these structure consists of two composite facesheets that is made of glass fibers reinforced polymer (GFRP) using the vacuum pump method and various cores that is made of poly lactic acid (PLA) using a fused depositional modeling (FDM). The main objective of this research is to design and manufacture a sample with more stored energy against impact and find the light sandwich structures, thus various cores is made of PLA. In this research, four different cores manufacture, which consisted of three different cores such as honeycomb, tubular and truss and two different thicknesses in the honeycomb core. Thus, in order to determine the role of the geometric shape of the core on its material properties, three different core shapes including honeycomb, tubular and truss are used. Also, to investigate the thickness effect, five and ten laminates in facesheet layers with honeycomb core are considered. The test results showed that the addition of five composite laminates reduces the specific stored energy by 64% and increases the maximum impact force for 11.4%. In this study, the effect of the geometric shape for the printed cores, the truss core stored more specific energy under the same impact conditions. Also, the truss core increased the stored energy 47% and 53% more than the honeycomb and tubular cores, respectively. Due to their unique properties, these structures can be mentioned in the aviation industry and wind turbines.

Assessment of numerical modeling approaches for thin composite laminates under low-velocity impact

Low-velocity impact behaviors of carbon/epoxy composite laminates have been widely investigated in recent years by using various numerical modeling approaches in which the specific damage initiation criterion, damage evolution method and interface model were employed. However, the computation accuracies of these approaches have rarely been compared and reported. To explore a high-precision modeling approach for low-velocity impact behaviors of laminated composites, numerical study focusing on a comparison of different failure criteria (Hashin/Puck), evolution methods (sudden/linear/exponential) and interface models (zero-thickness cohesive elements/finite-thickness cohesive elements/cohesive contact) was conducted. The dynamic mechanical responses and damage behaviors predicted by different modeling approaches were compared. A new damage index DˆI was proposed to characterize the extent of damage accumulation in each layer of laminates. The results indicate that the impact responses of the material are more influenced by the evolution methods rather than the failure criteria. The numerical results predicted with Puck criterion, linear evolution method, and finite-thickness cohesive elements are in the best agreement with the experimental data.

Effect of ageing conditions on the low velocity impact behavior and damage characteristics of aramid-basalt/epoxy hybrid interply composites

Polymer composites reinforced with aramid and basalt fibres are widely used in aviation, automobile, marine and civil structural components. In these applications, composites are often exposed to different environments involving temperature and humidity, which leads to the deterioration of mechanical properties and service life of the structure. This study aimed at investigating the influence of different ageing conditions on the low velocity impact (LVI) performance of 2-D aramid-basalt/epoxy interply composites. Compression molding method of fabrication was employed to prepare the hybrid laminates. LVI coupons were made as per the ASTM D3763 standard and aged in distilled water medium at three different temperatures namely, ambient condition (25 ℃), sub-zero condition (−10 ℃), and humid condition (40 ℃ and 60% relative humidity) until the specimens attain moisture saturation. After ageing, specimens were put through low velocity impact testing at two different impact energies of 10 J and 15 J and results were compared with the pristine specimens. Ultrasonic C-Scan and Scanning Electron Microscopy (SEM) were utilized to analyse the delamination due to impact and micro structural assessment of the pristine and aged specimens. Studies revealed that, specimens aged under sub-zero conditions showed better impact response compared to all other ageing conditions. Furthermore, fibre rupture, matrix decomposition, weakened fibre–matrix interface bonding and delamination were the major damages observed in aged specimens.

Effect of impactor velocity on low velocity impact behavior of Al/SiC monocoque interpenetrating composites

This study investigates the impact behavior and energy absorption characteristics of C4 composites under different initial energy conditions. The force-displacement responses were recorded using a conical impactor on an impact testing machine. Three configurations of C4 composites with varying pore sizes (10PPI, 20PPI, and 30PPI) were tested at three initial impact energies (208 J, 312 J, and 416 J). The force-displacement curves revealed that the 30PPI-C4 exhibited the highest force gradient and maximum force, followed by the 20PPI-C4 and 10PPI-C4. The maximum force increased with increasing impact energy for all configurations. Velocity attenuation during impact tests showed a correlation with deformation and collapse mechanisms of the C4 composite. Energy absorption analysis indicated that the 30PPI-C4 exhibited the highest energy absorption per unit mass, followed by the 20PPI-C4 and 10PPI-C4. Visual inspection revealed circular indentations and shear cracks on the top and bottom surfaces, with increasing damage area and depth of indentation at higher impact energies. The 30PPI-C4 demonstrated better resistance to indentation and failure, along with higher specific energy absorption. The refined grains in the 30PPI-C4 contributed to crack mitigation and energy absorption. The C4 composites with higher SiC volume percentages exhibited reduced damage area and higher stability during impact tests. The study concludes that the 30PPI-C4 composite with 18 vol% SiC foam shows superior impact resistance and energy absorption properties, making it a promising material for impact-related applications.

Low-velocity impact behaviour of biocomposite laminates reinforced by flax, basalt and hybrid fibres at various temperatures: Analytical, numerical and experimental results

In recent years, the non-biodegradable nature of synthetic composite materials has shifted the research focus on natural fibres as possible substitutes for traditional reinforcements. This paper investigates the effects of temperature variation on the impact behaviour of natural fibre laminates from an experimental, analytical, and numerical point of view. Flax, basalt, and hybrid/epoxy resin composites have been characterized through a variegated experimental campaign: from −40 °C to 80 °C. In addition to these studies, two different analytical models available in literature for synthetic materials are, here, combined and validated to reproduce the full loading–unloading trend of natural fibre composites. Since the aim of this study is the investigation of low-velocity impact behaviour as a function of the operating temperature, it is worth noting that no modifications have been made to these models, except for material parameters like Young’s and shear moduli. Subsequently, a finite element numerical investigation has been carried out, using the solver RADIOSS, with the aim of generating, in very reasonable computation times, a first numerical approximation of the experimental impact response. The obtained results show how both the presented procedures can predict well the response of these composites during an impact event. Moreover, the mixed trend observed in the hybrid configuration supports the thesis of hybridization’s importance, as a technique capable of exploiting the synergistic effects arising from the application of different types of reinforcement and reducing the drawbacks connected with the employment of a single type of fibre.

Experimental analysis on deformation and damage behavior of Al6061/SiC functionally graded plates under low-velocity impact

Due to their promising features provided by ceramic and metal constituents in a single volume, Functionally Graded Materials (FGMs) have received great attention for impact applications. Most of the available studies on the low-velocity impact behavior of FGMs have been carried out by analytical or numerical methods. This study addresses an experimental analysis on the low-velocity impact response of Al6061/SiC FGM plates. The influence of the material composition of the FGM plate (from metal-rich to ceramic-rich) on the energy absorption mechanisms as well as on the deformation and damage behavior was investigated. The ceramic-rich FGM plate exhibits a quasi-brittle response that includes a combination of elastoplastic indentation and brittle failures with increasing impact energy, while the metal-rich and linear FGM plates show elastoplastic behavior. Plastic deformation is the primary energy absorption mechanism for the metal-rich and linear FGM plates, whereas plastic deformation, brittle failures (radial cracks and conoidal crack/fracture), delamination, and pore collapse are effective on the energy absorption of the ceramic-rich FGM plate.

Effect of Temperature on the Low-Velocity Impact Behaviors of Engineered Cementitious Composite

Effect of Temperature on the Low-Velocity Impact Behaviors of Engineered Cementitious Composite

Experimental and numerical analysis of low-velocity impact behavior of wound products using multi-filament winding technique

The wound products are subjected to various impact loads during their service life, which caused invisible damage to the composite layers. In this paper, we investigated the failure behavior of composite layers fabricated using an innovative multi-filament winding (MFW) process under impact load. Firstly, the principle of the MFW technique was introduced. Finite element models were constructed for both novel and conventional techniques, and subsequent low-velocity impact (LVI) tests were performed to acquire the time-force and time-energy data for the CFRP (Carbon Fiber Reinforced Polymer) laminates. The test results were in good agreement with the LVI responses of the composites obtained from the simulations. The failure modes and microscopic damage of the composite layers of the two techniques were analyzed by scanning electron microscopy (SEM). The results showed that under the same impact velocity, three damage modes of fiber fracture, matrix cracking, and delamination were observed for both techniques. However, the composite layers of the MFW technique exhibited more excellent impact resistance properties in terms of maximum contact force, absorbed energy, as well as inter-laminar and intra-laminar damage. The MFW technique exhibits a notable level of winding efficiency and demonstrates exceptional performance of manufactured products, which can meet the increasing demand of winding products over the years.

Investigation of the effect of CNT reinforcement on low-velocity impact behavior of wooden plate honeycomb aircraft structures

Bu çalışmada, farklı kalınlıklı ahşap plakalı bal peteği uçak yapıları ve bunların yüzeylerine çok duvarlı karbon nanotüp (MWCNT) takviye uygulamak suretiyle düşük hızlı darbe davranışlarının incelenmesi ile çekirdek yüksekliğinin plakalarda oluşan hasara etkileri incelenmiştir. Ayrıca nano kompozit kaplamanın yüzey yapısalı üzerine olan etkilerinin tespiti ile hava araçlarında kullanılabilirliğinin araştırılması da amaçlanmıştır. Araştırmada akrobasi uçağına ait kanat yapısalından alınan 10 ve 30mm kalınlıklı 100x150mm ebatlarında karşılıklı olarak bir yüzeyi ahşap diğer yüzeyi %1 oranında karbon nanotüp (CNT) ile kaplanmış eşit sayıdaki numunelere 5J enerji seviyesinde darbe testi uygulanmış ve karşılaştırmalı olarak grafiklerle analiz edilmiştir. Testler 1.2549 m/s çarpma hızında yapılmıştır. Araştırma neticesinde CNT uçak yapısallarında takviyelendirilme sinin ağırlık artışına sınırlamalar dâhilinde etki etmezken aerodinamik yapıyı bozmadan mukavemet artışında olumlu sonuçlar verdiği ve mekanik özellikleri arttırdığı sonucuna ulaşılmıştır. Deneylerden elde edilen kuvvet-zaman, kuvvet-deplasman ve enerji zaman değişimlerinden elde edilen veriler grafikler yardımıyla açıklanmıştır.