Low Velocity Impact Research Articles

Analytical model of low-velocity impact penetration of sandwich panels with metal foam core and nanocomposite face sheets

This paper investigates the low-velocity penetration dynamic response of metal foam core sandwich panels with composite face sheets reinforced by nanoparticles. Based on the experimental results, an energy model is developed to predict contact force, impactor displacement, energy absorption, mechanisms of impact damage, and failure modes. An elastic–plastic–rigid (E–P–R) model is used to derive the energy absorbed by the metal foam. A stress function in terms of density ratio and strain is considered to predict the compression behavior of metal foam. The effect of nanoparticles investigated by the Halpin Tsai model. The analytical prediction is compared with the results of the experimental test and a reasonable agreement has been observed. The tested sandwich panel consisted of an aluminum foam core and an epoxy/carbon fiber face sheet reinforced with reduced graphene oxide (RGO). This model is useful for improving the design of sandwich panels with carbon fiber composite face sheet reinforced with nanoparticles and aluminum foam core. The results of impact test showed the addition of reduced oxide graphene increased the value of the first peak load by about 15%, the second peak load by about 36% and the amount of energy absorption in sandwich panel by about 18%. The radios of delamination and debonding reduced by 47% and 17.5%, respectively, compared to the sample without nanoparticles.

A comparison of damping-based methods to identify damage to carbon-fiber-reinforced polymers laminates subjected to low-velocity impact

A method for detecting low-velocity impact damage in carbon fiber reinforced polymer (CFRP) is presented. It involves the use of the Impulse Excitation Technique (IET) and hysteresis loops to calculate the damping parameter of T700/NCT304-1 carbon/epoxy samples subjected to various low-velocity impact energies. The value of the coefficient of restitution (COR) is determined for each impact, ranging between 0.62 for the lowest impact energy to 0.48 for the highest one. The results reveal that a three-step increase in the damping parameter exists in all cases as the impact energy on the specimen increases. An abrupt jump in the damping parameter value is observed for impact energies exceeding ∼0.9 of the material's maximum capacity. Overall, at the highest impact energy equal to 3.65 J, the damping parameter increased by 43.3% compared to the pristine specimen. Additionally, two cases of cyclic tension-tension loading were applied to the specimens, with maximum stresses set at 150 MPa and 200 MPa. The measured values of plastic and elastic strain energy were used to determine the damping ratios. For both cases, the damping of the specimen subjected to the highest impact energy was ∼1.2 times greater than that of an intact specimen, with an increase pattern similar to the findings of the IET method. Optical microscope images of the specimens are provided to illustrate various damage modes observed in the composite materials.

In-plane compression behaviors of novel reentrant double arrowhead honeycombs with two plateau stress regions

Combining reentrant honeycomb (RH) and double arrowhead honeycomb (DAH), the reentrant double arrowhead honeycomb (RDAH) is proposed. The deformation modes and compression behavior of the RDAH are numerically simulated and compared with the RH. The results show that the RDAH has a better specific energy absorption SEA than the RH regardless of low velocity or high velocity impact. Compared with the RH, the SEA of the RDAH increased by 9.4% under an impact velocity of 1 m/s and increased by 24.4% under an impact velocity of 100 m/s. The mechanical properties of the RDAH under different impact velocities and relative densities were further discussed, and empirical formulas were established based on the deformation mode map to predict the dynamic bearing capacity of the RDAH. Finally, the influence of the cell number on the in-plane compression of the RDAH is discussed, and it is found that an RDAH larger than 4 × 4 can produce more stable deformation. The influence of different cell vertical ligament heights h and relative densities on the mechanical properties of the RDAH is researched parametrically. The increase in the unit vertical ligament height h will reduce the SEA and destroy the stable deformation of the RDAH. SEA increases almost linearly with increasing relative density.

Investigation on impact properties of basalt and glass fiber reinforced polyester composites filled with nano silica

The relevance of granite waste is growing alongside the global demand for granite. This waste comprises various forms, including large granite pieces, tiny fragments, dust, and other debris. This research aimed to create a novel composite by incorporating nano silica from granite powder as a filler, combining it with basalt and glass fibres as the matrix, and using polyester as the resin. The fabrication involved Fiber Reinforced Composite (FRP) production through hand lay-up and vacuum silicon moulding to eliminate trapped air during lamination. After fabrication, tests were conducted for hardness, density, and Low-Velocity Impact under dropping weight. The results indicated that introducing nano silica as a filler in polyester resin positively impacted Basalt Fiber Reinforced Polyester Composite (BFRPC) and Glass Fiber Reinforced Polyester Composite (GFRPC). Analysis showed that as the nano-silica content increased, so did energy absorbed, impact strength and ductility index, up to a 1wt% nano-silica concentration. Beyond this point, agglomeration occurred, causing a decrease in these values. The 1 Nano silica Basalt Fiber Reinforced Polyester Composite (1NSBFRPC) material exhibited the highest energy absorption at 103.21J, indicating strong impact strength at 21.27kJ/m2. Conversely, the 1NSGFRPC material demonstrated the highest ductility index at 4.13. In comparison, Carbon Tech Global's (CTG) energy absorption, initially 25.56J, experienced a significant increase of 303.79%, reaching 103.21J. The impact strength also showed a notable shift, escalating by 396.96% from 4.28 KJ/m2 to an impressive 21.27kJ/m2. This shift in impact strength represented a remarkable 128.2% surge, highlighting the significant influence of integrating nano-silica. This new composite suits truck body carriers and offers environmental benefits. Furthermore, utilising nano silica in this context not only aids in waste reduction within the granite sector but also contributes to sustainable resources.

Investigating the energy absorption properties of sandwich panels filled with shear thickening fluid with a weight fraction of 35% under low-velocity impact

This research study the energy absorption performance of aluminum core honeycomb sandwich panel (ACHSP) with filled and empty cores subjected to low-velocity impact testing, with diverse skins; (i) aluminum sheets, (ii) 5-ply epoxy glass composite, and (iii) 5-ply shear thickening fluid (STF)-impregnated glass fabrics. The prepared STF was 35 wt% and the impactor heights was selected at 100 and 500 mm to assess the effect of different impact velocities on the energy absorption capability of STF. The specific energy absorption (SEA) of the STF-filled ACHSP with 5-ply STF-impregnated fabrics skin (height of 500 mm) compared to STF-filled ACHSP with aluminum sheets skin and 5-ply epoxy glass composite skin have increased by 28.38 and 21.79%, respectively. In a fact of truth, when the external force is applied to the STF-filled ACHSP, the fluid transitions from a low-velocity to a high-velocity state instantly. This transition exerts forces on the suspended particles within the fluid. Actually, during the impact, the particles come into close contact and form temporary particle networks or chains. These networks increase the viscosity of the fluid, making it resistant to flow. The energy of the impact is then absorbed by the formation and reformation of these particles’ networks. However, the SEA of STF-filled ACHSP at the height of 500 mm to empty ACHSP at the height of 100 mm have decreased significantly, and the energy absorption of STF-filled ACHSPs to corresponding empty ACHSPs have increased remarkably.

Dynamic and electrical responses of a curved sandwich beam with glass reinforced laminate layers and a pliable core in the presence of a piezoelectric layer under low-velocity impact

Dynamic and electrical responses of a curved sandwich beam with glass reinforced laminate layers and a pliable core in the presence of a piezoelectric layer under low-velocity impact

Adaptive Multi-Fidelity (AMF) modelling of damage in composites under Low-Velocity impact and compression after impact

In this paper, the recently developed adaptive multi-fidelity (AMF) approach is extended for progressive damage analysis of composite laminate subjected to low-velocity impact (LVI) and compression after impact (CAI). This approach is more computationally efficient by utilizing a combination of low-fidelity shell elements and high-fidelity brick elements in a single concurrent model. A general set of criteria has been proposed to govern the transition of shell and brick elements from one to the other and vice versa, as dictated by the mechanics of damage evolution. When matrix cracks or interfacial delamination initiates, shell elements transit to brick elements and cohesive elements are inserted to capture the damage growth. The brick elements partitioned by non-critical cracks are reverted to smeared shell elements when the numerical crack density becomes saturated in a laminate. Geometrical non-linearity is adopted here to predict large deformation in the composite laminate for both implicit quasi-static and dynamic analyses. The performance of AMF models is benchmarked with high-fidelity models and experimental data reported in literature. The predicted results show reasonable agreement with experimental observation and high-fidelity models, and up to 51% improvement in computational efficiency is achievable.

Characterization of low-velocity and low-energy responses of elastic-plastic plate struck by elastic-plastic impactor

This paper presents a study on the characterization of low-velocity and low-energy impact responses of elastic-plastic plate struck by elastic-plastic spherical impactor. The applicability of the existing impact characterization diagram is examined firstly by intensive finite element (FE) simulations for a wide range of complicated impact situations including all three types of contact: indentation, flattening and combined flattening and indentation. The limitations of the existing diagram are found in identifying the type of impact response and predicting the maximum impact force for complicated impact situations. The effects of elastic and plastic deformations of impactor on the identification and prediction by the existing diagram are analyzed. A new linear contact law is presented according to the piecewise linear characteristics of contact stiffness observed from the intensive FE results. An extended impact characterization diagram is then proposed to characterize low-velocity and low-energy impact responses of plate under complicated impact situations with arbitrary three contact types. The extended diagram is validated by the intensive FE simulations and experimental results. It is concluded that the extended impact characterization diagram can identify correctly the plate response type to complicated impacts and predict accurately the maximum impact force in a fast and simple way without the aid of FE models and experimental tests.

Dynamic characterization and damage analysis for the thermoplastic fiber-reinforced epoxy composites exposed to repeated low velocity impact

In the current study, contrary to conventional fiber-reinforced composites, polyamide fiber was used as reinforcement material, and the effects of thermoplastic fiber reinforcement on repeated low velocity impact (LVI) responses of composites were examined. In this regard, polyamide fiber-reinforced composites were fabricated using the vacuum-assisted hand lay-up method (VAHLM) and then exposed to repeated LVI loadings. Experimental tests were performed on the specimens for 100 impacts with a constant velocity of 3 m/s, which is equivalent to 25.2 J, and the impacts of repeated LVI loadings on the dynamic responses such as peak force, energy absorbing/rebounding, total impulse, bending stiffness and contact stiffness were examined. Moreover, the damage mechanisms resulting from the relative damage accumulation depending on the impact numbers were examined. According to the findings, the thermoplastic polyamide fibers absorbed more than 60% of the applied energy, and the absorbed energy increased with ascending impact number. Furthermore, the thermoplastic fiber-reinforced epoxy composites gained stiffness with increasing impact, which was linked to the thermoplastic chain structure. Despite quite a number of impact loadings, no serious damage mechanisms such as fiber breakage, perforation, or penetration were observed, and the specimens maintained their structural integrity. Due to the higher energy absorption of thermoplastics, the utilization of polyamide fibers in composites has been found to be well suited for applications subjected to repeated impacts.

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.

Study on low-velocity impact response of kevlar/epoxy-polyurethane sandwich panels

This study aims to investigate the maximum energy absorption of sandwich panels featuring composite facesheets and a polyurethane foam core under low-velocity impact. The research explores various impactor head geometries, fiber orientations, and the number of composite layers on the panel facesheets. Three different impactor heads with flat, hemispherical, and conical shapes were used for experimental impacts. Numerical simulations were performed using Abaqus/Explicit finite element software, with damage initiation in the composite layers determined by the three-dimensional Hashin criterion. The results revealed that the conical-head impactor caused the highest energy absorption, accompanied by the greatest displacement and velocity changes. Among specimens with different fiber orientations, the 60° fiber layers exhibited a 9.41% and 8.45% higher maximum force compared to the 30° and 45° fiber layers, respectively. Furthermore, the study investigated the influence of the number of composite layers in the facesheets. It was found that panels with more layers in the bottom facesheet demonstrated a 4.94% increase in energy absorption compared to panels with more layers in the top facesheet. This research provides valuable insights into optimizing sandwich panel designs for enhanced energy absorption during low-velocity impact scenarios.

Low-velocity impact and post-impact compression properties of carbon/glass hybrid yacht composite materials

In the field of maritime engineering, low-velocity impact (1-10 ms−1) is typically regarded as a quasi-static event. During navigation, yachts are inevitably subjected to low-velocity impact from floating objects in the water, and may also encounter compression after low-velocity impact. This study employs a combined approach of numerical simulation and experimental testing, aiming to investigate the damage and failure mechanisms of yacht composite laminates under conditions of low-velocity impact and post-impact compression (CAI), and by SEM and ultrasonic C-scanning the damage characteristics of different layup samples was studied in impact and compression tests. In order to conduct a more in-depth study on the damage evolution and failure mechanisms of yacht composite laminates, a three-dimensional damage model is established based on the continuum damage mechanics, and a physico-mechanical failure criterion combining the 3D Hashin and Puck criteria is employed. This criterion is used to capture the initiation points of damage in both fibers and matrix. Additionally, a bi-linear damage constitutive relationship is utilized to describe the damage evolution. Interlayer delamination is addressed through simulating the bonding behavior of interfaces. The numerical results show good correlation with the experimental results, which validates the effectiveness and rationality of the proposed numerical model. The study shows that laying carbon fiber cloth in the middle of the sample exhibits excellent impact resistance; laying carbon fiber cloth at the bottom exhibits better deformation resistance and stronger residual compression performance. Considering the three aspects of deformation, residual strength, and damage area, laying carbon fiber cloth in the first layer exhibits better mechanical properties, which provides useful reference for the design and manufacture of yacht materials and helps to improve the safety and reliability of yachts.

Effect of nano hybrid additives on low velocity impact responses of aramid composite plates: example of CNT and ZrO2

Aramid reinforced composites are advanced materials that are widely used in many industrial applications thanks to their combination of high strength and lightness. Nano additives are of great importance for improving the mechanical properties of aramid reinforced composites and reducing costs. In this paper, multi-walled Carbon Nanotube (CNT) and Zirconia (ZrO2) nano hybrid additives were used to determine the effect on the mechanical characterization of aramid composite plates. Therefore, low velocity impact responses of aramid fiber reinforced composites were investigated by adding ZrO2 and CNT nano hybrid additives to the Polives 701 polymer vinylester resin matrix. Low velocity impact tests were carried out at 10 J and 15 J. As a result of the experiments, the effects of nano hybrid additives on the impact absorption properties of aramid composite plates were determined. By determining the maximum force, displacement and time values, the effect of CNT and ZrO2 nano hybrid additives on the impact resistance of the composite plates was analyzed. In addition, it contributed to the development of composite materials used in industrial applications by providing information on increasing the performance of composite materials by using nano additives. As a result of this study, it was determined that the strength of the composite material increased proportionally when the CNT additive was used, and the material became embrittled when the ZrO2 additive was used.

Investigating the influence of High-Void content on the impact and Post-Impact properties of Flax/Epoxy composite laminates with different stacking configurations

Defects in composite materials, such as voids, significantly impact their long-term performance and should be carefully considered in the design process of engineering structures. This study investigates the effects of high void content on the impact and post-impact properties of pure Flax/Epoxy (FE) composite laminates. Three main configurations, namely cross-ply (CFE), angle-ply FE (AFE), and quasi-isotropic FE (QFE), are examined using drop-weight impact and three-point bending tests. The results reveal distinct behavior among the configurations. The drop-weight impact test results show that the AFE configuration exhibits 3.5 % and 6.45 % higher impact resistance compared to CFE and QFE, respectively. to the increase of the impact energy to 15 J amplifies the differences to 9.31 % and 19.11 %. Also, post-impact flexion tests demonstrate a significant decline in flax composite resistance by 14 % for CFE, 26 % for QFE, and AFE. Furthermore, the overall impact and flexural properties of the FE composites are not significantly affected by the void content. However, it has a major impact on the damage mechanism that is ispected visually and through X-ray tomography, emphasizing the importance of considering the void content in the design and analysis of such flax composites. The proposed numerical model to predict the onset of damage and damage evolution in these composite materials under low velocity impact show a good greement with the experimental results.

The force and dynamic response of low-velocity projectile impact into 3D dense wet granular media

The presence of liquid bridges between particles in a wet granular media gives rise to capillary forces at the microscopic scale that dramatically alters the material's microstructure and macroscopic responses. Previous experimental studies show significant differences in the penetration depth of the projectile into assemblies of dry or wet particles. Still, there is a lack of fundamental understanding of the difference induced by the presence of liquid bridges in dynamic regimes. In this study, the contact model parameters of wet glass beads are calibrated employing the angle of repose tests and cylinder lifting tests, and a series of three-dimensional discrete element method simulations of spheres impact into wet granular packings are conducted. The dynamic characteristics of the projectile are obtained numerically and found to be in good agreement with the experimental data. The analyses indicate that the final penetration depth in the wet granular media is linearly related to the initial velocity and has a power function relationship with the impact energy. The generalized Poncelet law is suitable for wet granular materials, but the presence of liquid significantly affects the values of the parameters. There is a velocity “stagnation zone” at the initial stage of the wet granular impact, and the final penetration depth and the duration interaction time are smaller than that of the dry case. The difference can be attributed to the resistance evolution of the projectile exerted by particles and gives the parameter scaling law of the peak impact force. Further, a macro-micro transition technique is employed to characterize the velocity field, pressure field, and stress field inside the wet granular media and the spatial distribution is quantified based on stress theory.

First classification of iron meteorite fragment preserved in Chang’e-5 lunar soils

Lunar soil preserves numerous fragments of meteorites impacting on the Moon, providing a unique opportunity to investigate the distribution of the types of projectiles over billions of years. Here we report the first discovery of an iron meteorite fragment from the Chang’e-5 lunar soil, which consists mainly of martensite (quenched from taenite), kamacite, and schreibersite, with a trace of pentlandite. The meteorite fragment is Ni- and P-rich, S-poor, and based on its mineral chemistry and bulk composition, can be classified into the IID-group, a rare and carbonaceous group of iron meteorite originating in the outer Solar System. This meteorite fragment experienced only limited partial melting followed by fast cooling, suggestive of efficient preservation of intact remnants of iron meteorites impacting on the porous lunar regolith. Alternatively, it is a relic of a low-velocity impact of submillimeter-sized metal grains originated from an IID-like iron meteorite. Our observations demonstrate that it is feasible to achieve the type distribution of meteorites impacting on the Moon via systematically analyzing a large number of metal grains separated from lunar soils, thus shedding light on the dynamic evolution of the Solar System.

Low velocity impact and compression-after-impact response of hybrid pseudo-woven meso-architectured carbon/epoxy composite laminates manufactured via automated fiber placement

An experimental study is presented on the low velocity impact (LVI) and compression after impact (CAI) response of T800-SC carbon/epoxy laminates manufactured via automated fiber (AFP) placement manufacturing. Two hybrid laminate configurations consisting of unidirectional and pseudo-woven meso-architectured composite (MAC) sub-laminates are compared against a traditional quasi-isotropic control laminate. MAC sub-laminates are manufactured via a modified AFP process implementing tow skips. The MAC architecture is macroscopically heterogeneous with discontinuous and spatially varying fiber orientations both in-plane and through thickness resulting in multiple interfaces and an expanded design space. The laminates are tested under LVI energies of 15–55 J using a 25.4 mm diameter hemispherical projectile according to ASTM D7136. The results show similar load-displacement responses but significant difference in the LVI damage profiles and CAI strengths for the different configurations. The hybrid laminate configurations exhibit increased damage resistance with up to 37% higher critical delamination load and increased damage tolerance with 26% higher residual compressive strength after an impact of 55 J compared to control laminate.

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.

Strain rate-dependent failure modelling of impact damage in laminated CFRP structures

This work focuses on the development, implementation, and validation of a constitutive model for unidirectional composites, aiming to numerically simulate impact damage in laminated structures. The model incorporates a failure criterion that accounts for the influence of strain rate on failure initiation and distinguishes between four failure modes. Failure initiation criteria are 3D phenomenological-based criteria according to the previous work of Puck and Schürmann (1998) and Pinho (2006). Additionally, a mesh-objective damage propagation model is implemented to simulate the impact damage. The impact simulations are performed using Abaqus/Explicit, with the constitutive model implemented through the user subroutine VUMAT. Validation of the strain rate effects on failure initiation is performed using strain rate-dependent bi-axial failure curves for IM7/8552 and AS-4/3506. The analyses indicate that the properties governing the strain rate dependence of failure initiation are consistent. Therefore, the hypothesis was tested in which the same strain rate scaling approach could be used for CFRP materials for which only static properties are available. This hypothesis was tested in high and low-velocity impact simulations at laminated IMS60/977–2 CFRP plates. The results demonstrate that the model accurately replicates the experimentally observed impact-induced contact forces and effectively captures the damaged state in the impacted plate.

Study of the dynamic response and damage evolution of carbon fiber/ultra-thin stainless-steel strip fiber metal laminates under low-velocity impact

Two configurations of carbon fiber/ultra-thin stainless-steel strip fiber metal laminates (CUSFML) with differing metal volume contents (35.3% and 18.2%) and carbon fiber-reinforced polymer (CFRP) composite laminates were selected for tests. The impact response and the effect of metal volume content on the impact resistance of CUSFML were assessed via experiment and FEM. Inducing damage by drop-weight test within the impact energy range of 18.60–46.23 J, two types of CUSFML and CFRP composite laminates were compared. In particular, the bearing capacity, impact deflection, failure modes, and energy dissipation were considered. The impact modeling using the VUMAT subroutine refines the relationship between energy-dissipating mechanism and damage evolution. The results indicate that CUSFML are characterized by higher impact resistance than CFRP composite laminates under low-velocity impact. The effect of metal volume content on the impact resistance increases gradually with impact energy increasing. Under 46.23 J impact, the CUSFML with higher metal volume content exhibits more concentrated damaged area with severe penetration failure, which is more dominated by metal failure features with a higher proportion of plastic energy dissipation. For CUSFML with lower metal volume content, extensive delamination and damage expansion occurs under the dominance of fiber damage behaviors.