Low-velocity Impact Experiments Research Articles

Impact response characteristics and damage mechanism of continuous carbon-fiber-reinforced magnesium matrix composite materials

The continuous carbon-fiber-reinforced magnesium matrix composite (C_f/Mg) is a new type of composite material made of a magnesium alloy sheet and carbon-fiber-reinforced composite material with alternating layers. It has the advantages of high damage tolerance, light weight, and corrosion resistance, and has become the first choice of lightweight materials in aerospace, transportation, and other fields. Because impact-resistance serves as an important index for its structural design and performance stability, a continuous carbon-fiber-reinforced magnesium matrix composite with indirect bonding using a modified epoxy resin was designed in this study. Moreover, C_f/Mg was chosen to be the object of research through the selection of constituent materials such as magnesium alloys, carbon fibers, resins, and other properties, which matched the aim of realizing a lightweight material. With the help of hot-compression molding technology, dynamic impact mechanical behavior, and damage analysis technology, the structural design and preparation process optimization of epoxy resin carbon-fiber prepregs and magnesium alloy layer materials, as well as the dynamic impact mechanical response characteristics and damage evolution process under different impact energy conditions, were studied. Accordingly, through a combination of low-velocity impact experiments and numerical simulations, the effects of continuous multiple impacts at the same location with the same impact energy, as well as impacts with the same impact energy and different punch diameters, on the low-velocity impact damage behavior and dynamic impact response characteristics of C_f/Mg were investigated. The results of this study show that when the 5J impact is applied four times consecutively, the peak impact load gradually increases with the increasing number of impacts. Moreover, the peak impact loads of the second, third, and fourth impacts increase by 6.09%, 10.7%, and 14.5%, respectively, compared with the results of the first impact.

A constitutive model for shear thickening fluid (STF) impregnated Kevlar fabric subjected to impact loading

A constitutive model is presented herein to predict the response and failure of STF impregnated Kevlar fabric under impact loading on the basis of the progressive damage model for fibre reinforced plastic (FRP) laminates. In the constitutive model, the strain rate effect of shear strength is innovatively connected with the rheological property of STF. In order to verify the validity and accuracy of the model, numerical simulations of both ballistic and low-velocity impact experiments of STF impregnated Kevlar fabric are conducted. Furthermore, parametric study is carried out on the influences of impact velocity and rheological behavior of STF. It transpires that the numerical results using the constitutive model are in good agreement with the experimental data in terms of residual velocity, load-displacement curve, energy absorption, global deformation and failure patterns. It also transpires that, with the same impact energy, STF impregnated Kevlar fabric shows stronger resistance to lower velocity ballistic impact. In addition, the maximum viscosity and shear thickening interval of the STF have a significant effect on the ballistic performance of the STF impregnated Kevlar fabric.

Experimental and Numerical Investigation of Dynamic Damage and Load Transfer of PBX Substitute Material under Low Velocity Impact.

The accidental initiation of explosives under mechanical loads has caused numerous catastrophic events. Therefore, the dynamic damage behavior of confined polymer-bonded explosives (PBXs) must be assessed to improve their practical applicability. In this study, polymer-bonded sugar (PBS) materials were prepared using a novel agglomerate to develop a PBX substitute material with enhanced experimental safety. The mechanical properties of the PBS shell were evaluated using a dynamic compression test, which revealed that the compression response of the shell was affected by the strain rate. A low-velocity impact experiment was performed to investigate the dynamic damage and load transfer characteristics of the PBX substitute. A constitutive model was developed to characterize the mechanical response of PBS subjected to high strain rates, and implementing this model in ABAQUS ensured successful prediction of the damage evolution process associated with PBS. Simulation results indicated that the PBS specimen was primarily damaged around its center while sliding friction was dominant near the center during pressure application. Notably, different stress states result in distinct crack growth velocity histories along the axial direction, with the damage ratio progressively decreasing toward regions closer to the impact surface.

Research on the adaptability of STF-Kevlar to ambient temperature under low-velocity impact conditions

Composite fabric formed by combining shear thickening fluid (STF) with aramid fabric (Kevlar) exhibits heightened impact resistance, rendering it extensively utilized within the realm of energy absorption. Given that composite fabrics often encounter various low-velocity impact scenarios in daily use, such as object falls, this study conducts rheological property tests and low-velocity impact experiments at different ambient temperatures to unveil the correlation between the low-velocity impact resistance of STF-Kevlar and environmental temperature. Rheological tests indicated that as temperature decreased, shear thickening behavior became more prominent, resulting in higher viscosity. Low-velocity impact tests demonstrated that with increasing temperature, the capability to withstand low-velocity impact gradually diminished in both STF and neat Kevlar, whereas the anti-impact property of STF-Kevlar increased. At a temperature of 60 °C, the peak load experienced by STF-Kevlar during low-velocity impact reached 1627 N, marking a notable 300% increase compared to the 407 N observed for neat Kevlar. Under changing environmental temperatures, alterations in the low-velocity impact resistance of STF-Kevlar were not contingent upon STF's viscosity but rather correlated with inter-yarn friction. The elevated inter-yarn friction at low temperatures hindered yarn sliding, leading to a decrease in the impact resistance of STF-Kevlar.

Study on impact properties of carbon/kevlar fiber hybrid composites

AbstractIn this article, carbon/kevlar hybrid composites were prepared using Vacuum Assisted Resin Infusion (VARI). The sandwich structure with plain carbon weave fabric as the core layer and plain kevlar weave fabric as the surface layer was selected as reinforcement and the solution of epoxy resin and curing agent was selected as matrix. The low velocity impact experiment and compression after impact (CAI) experiment were carried out on the samples at different hybrid ratio and different temperatures, and the mechanical response on the impact loads were analyzed respectively. The results show that the specimen can limit the delamination defect expansion of the surface kevlar fiber as the carbon fiber used as the core layer, which reduce the delamination defect area and improve the impact resistance of the sample. The toughness of the sample improves the brittle failure mode, that is, the sample still has a certain bearing capacity after the load exceeds the maximum strength, the sandwiched composites presents a positive hybrid effect. With the increase of temperature, the matrix was obviously softened, the macromolecular movement in the system was intensified, the three‐dimensional network macromolecular structure of the matrix and the fiber/matrix interface properties were damaged, and the mechanical properties showed an obvious downward trend. As far as the influences of hybrid ratio and temperature on impact behavior of composite are concerned, it lay a theoretical foundation for the industrial application of carbon/kevlar hybrid composites.Highlights The sandwiched structure was used to design the composites, which greatly improves the impact properties of the specimens. The impact properties and compression after impact properties at different hybrid ratios and different temperatures were studied. Based on the hybrid effect and temperature effect, the impact failure mechanism of the sample was analyzed.

Low-velocity impact experiments of porous ice balls simulating Saturn's ring particles: Porosity dependence of restitution coefficients and the mechanism of inelastic collision

We investigated the porosity dependence of the restitution coefficient (ε) of porous ice balls with porosities of 49.6%, 53.8%, and 60.8% colliding with granite, ice and porous ice plates at a low impact velocity (vi = 0.93–96.9 cm s−1) and temperature of −13.8 °C. The relationship between the impact velocity and the restitution coefficient was divided into two regions by the critical velocity vc: In the quasi-elastic region (vi≤vc), the restitution coefficient had a constant value of εqe regardless of the impact velocity and could be explained by using Dilley's viscous dissipation model. In the inelastic region (vi≥vc), the restitution coefficient decreased with the impact velocity and could be explained by using the improved Andrews' plastic deformation model. We then determined the porosity dependence of the εqe and vc empirically for collisions between the porous ice ball and the porous ice plate from our results. Then we extrapolated the porosity dependence of the restitution coefficient by substituting the calculated εqe and vc for the porosity of 10 to 70%. The restitution coefficient was found to decrease with increasing porosity of the porous ice, and to be strongly dependent on the porosity of the porous ice. Considering the energy budget in the steady-state dense ring system which is controlled by the restitution coefficient of the ring particles, the velocity dispersion of the ring particles was estimated to be ∼10−2 mm s−1 to cm s−1 for the ring particles with the porosity from 45% to 70% and < 10–90 cm s−1 for those with the porosity <45%.

Effect of ultraviolet radiation on the low‐velocity impact and compression after impact performances of aerospace composite laminates

AbstractThe low‐velocity impact (LVI) characteristics and compression after impact (CAI) properties of aircraft composite laminates under the influence of ultraviolet (UV) radiation were studied. Firstly, 0, 30, 60, 90 days of UV radiation experiments were carried out on the specimens to analyze the characteristics of the surface topography. Secondly, LVI experiments, the impact energies of 10, 17, and 25 J, were carried out on specimens to analyze the impact response laws and the characteristics of the impact instantaneous deformation. Finally, through CAI experiments and scanning electron microscope (SEM) techniques to clarify the influence mechanism of UV radiation on the residual compressive strength of specimens. The results showed that with the increase of UV radiation time, the shrinkage and erosion phenomena of the surface matrix and the exposure degree of the surface fibers were gradually increased, and the surface fibers were completely exposed after 90 days of radiation. At the same impact energy, with longer radiation time, the peak force gradually decreased (from 8673.86 to 7851.68 N at 17 J), the absorbed impact energy (from 9.48 to 11.13 J at 17 J) and maximum displacement (from 4.1 to 4.73 mm at 17 J) increased, the depth of pit on the impact surface decreased (from 0.213 to 0.14 mm at 17 J), and the internal damage projection area increased (from 906.68 to 1158.66 mm2 at 17 J). The compression damage of the specimens not exposed to/ exposed to UV radiation was mainly fiber cracking/interlayer delamination, respectively.Highlights Ultraviolet (UV) radiation makes the matrix of surface shrink, the fibers exposure increase. The Stage II has obvious oscillation phenomenon in four stages of the low‐velocity impact process. With prolonged UV radiation, the projected area of internal damage expands. The residual compressive load increases with the increase of UV radiation time.

Crushing behavior of multi-layer lattice-web reinforced double-braced composite cylinders under lateral compression and impact loading

This paper reports on the crushing behavior of several novel multi-layer lattice-web reinforced double-braced composite cylinders composed of glass fiber reinforced polymer (GFRP) face sheets, GFRP lattice webs, polyurethane (PU) foam core and steel bars. A series of quasi-static lateral compression and low-velocity impact experiments were carried out to investigate the feasibility of the proposed cylinders. All the experimental specimens were manufactured using a vacuum assisted resin infusion process (VARIP) method. The bearing capacity and energy absorption performance of the composite cylinders can be significantly improved with the enhancement of multi-layer lattice-web layout and use of bracing. Among the proposed three types of lattice-web layouts, the double-layer dislocated lattice-web layout made the composite cylinder exhibit the greatest specific energy absorption (SEA) performance and good impact resistance property and can be chosen as an optimal configuration. Furthermore, numerical models were established using LS-DYNA software to simulate the large deformation of the composite cylinders with double-layer dislocated lattice-web layout. Based on the numerical models, parametric analysis was carried out to discuss the effects of various parameters on the crushing behavior of the composite cylinders. The bearing capacity and impact resistance property can be generally improved with the increase of GFRP thickness or radial lattice-web height. Additionally, using stronger foam material or smaller inclination of bracing can increase the absorbed energy in PU foam but the GFRP material always makes an essential contribution to the energy absorption of the composite cylinders.

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.

Cell-filling reinforced materials for improving the low-velocity impact performance of composite square honeycomb sandwiches: Polymethacrylimide foam vs. aluminum foam

In this study, PMI foam and aluminum foam are used as reinforcement materials for filling the cells of carbon fiber-reinforced composite square honeycomb sandwiches (CSHSs), forming two new sandwich structures, namely, PMI foam-reinforced CSHS (PRCSHS) and aluminum foam-reinforced CSHS (AFRCSHS). The impact resistance and residual flexural performance of the composites is compared by using low-velocity impact (LVI) and three-point bending (3 PB) experiments. The different impact energy levels of 25 J, 50 J, 65 J, and 100 J are applied. The impact and bending failure process and failure mechanism are analyzed using a combination of industrial computed tomography (ICT) and scanning electron microscopy (SEM). PRCSHS and AFRCSHS are compared for various enhancement effects and their resulting lightweight features. The residual flexural and impact resistance properties of the two sandwiches improved significantly. Compared with CSHS, the maximum impact load of PRCSHS and AFRCSHS increased by 115.6% and 78.9%, respectively. Moreover, the impact energy absorption, residual flexural load, and residual flexural energy absorption increased by 30.9% and 21.3%, 80.7% and 58.5%, and 173.1% and 84.3%, respectively. The PRCSHS was noticeably lightweight, but AFRCSHS was not sufficiently lightweight. The qualitative results of comparison of the two reinforcement materials in this study can be extended to other carbon fiber-reinforced all-composite 2D honeycomb sandwiches.

The influence of asymmetric faces on low-velocity impact failure of CFRP/aluminum foam composite sandwich beams

The influence of asymmetric faces on dynamic failure of fully clamped CFRP/aluminum foam composite sandwich beams subjected to low-velocity impact was studied. Three kinds of geometrically asymmetric sandwich cross-sections with an equal area density were designed. The low-velocity impact experiments of the composite sandwich beams were carried out to explore the dynamic response and the failure modes. Initial failure modes of top face fracture, indentation and core shear were found. The final failure modes, including top face fracture, core shear, bottom face fracture at one end and debonding between core and bottom face, were observed. It is shown that the composite sandwich beams experience the elastic bending to large deflection. The impact load is strengthened and increases rapidly at the large deflection stage due to effect of the fully clamped boundary. Furthermore, the quasi-static theoretical models were employed to predict the dynamic response of the composite sandwich beams. the theoretical models can capture the elastic bending of the composite sandwich beams reasonably, while the initial failure loads are slightly underestimated. The comparisons of peak load and midspan deflection suggest that the asymmetric composite sandwich beams with a thinner top face have better impact resistance than other designs of the faces.

Failure mechanism and impact resistance of all GFRP Miura-ori with platforms sandwich structure under low-velocity impact experiments

The traditional Miura-ori was optimized to Miura-ori with platforms by geometric parameters. Two types of impactors were used to conduct low-velocity impact experiments at two specific sites. The damage morphology, response characteristics, and failure mechanism under various energy were systematically investigated. The results reveal that the impact resistance of the node is better than that of the base due to crushing absorbing energy. The impact resistance of the Miura-ori with platforms sandwich structures to the flat-ended impactor is better than that of the hemispherical impactor at the node. Still, the performance at the base is the opposite.

Impact response of a sandwich with a foam aluminum core enhanced by a ceramic tile: An experimental study

This research proposes using a hybrid core consisting of foam metal and a ceramic tile to enhance the impact resistance of the sandwich construction. We assess the impact response of such an enhanced sandwich under a low-velocity drop-hammer load. Two thicknesses and three positions of the ceramic tile were considered. The low-velocity impact experiment was performed with a 16 mm hemispherical hammerhead and an impact energy range of 30–70 J. The results indicate that the ceramic tile significantly increases the impact resistance of the sandwich. A sandwich with a ceramic tile in the middle of the aluminum foam core had the highest peak force, perforation resistance, and energy absorption. Moreover, the performance was better for the thicker ceramic tiles, and the different damage patterns of the post-mortem sandwiches were analyzed. The underlying mechanisms of enhanced performance are discussed schematically in detail for the sandwiches. These results indeed showed that this proposed sandwich construction could be considered as a potential candidate in high-performance protective component.

Electrospun Polyvinylidene Fluoride Piezoelectric Fiber Glass/Carbon Hybrid Self-Sensing Composites for Structural Health Monitoring.

In this study, a polyvinylidene fluoride (PVDF)/graphene nanoplatelet (GNP) micro-nanocomposite membrane was fabricated through electrospinning technology and was employed in the fabrication of a fiber-reinforced polymer composite laminate. Some glass fibers were replaced with carbon fibers to serve as electrodes in the sensing layer, and the PVDF/GNP micro-nanocomposite membrane was embedded in the laminate to confer multifunctional piezoelectric self-sensing ability. The self-sensing composite laminate has both favorable mechanical properties and sensing ability. The effects of different concentrations of modified multiwalled carbon nanotubes (CNTs) and GNPs on the morphology of PVDF fibers and the β-phase content of the membrane were investigated. PVDF fibers containing 0.05% GNPs were the most stable and had the highest relative β-phase content; these fibers were embedded in glass fiber fabric to prepare the piezoelectric self-sensing composite laminate. To test the laminate's practical application, four-point bending and low-velocity impact tests were performed. The results revealed that when damage occurred during bending, the piezoelectric response changed, confirming that the piezoelectric self-sensing composite laminate has preliminary sensing performance. The low-velocity impact experiment revealed the effect of impact energy on sensing performance.

CFRP cylindrical tubes equipped with thin-walled semi-circular lateral corrugated inner stiffeners subjected to quasi-static latitudinal impact

Recently, versatile tubes with different cross-sectional cores have been suggested to reduce impact failures of protective structures. One method for improving cylindrical tube bending stiffness is using thin-walled corrugated cores. This paper investigates the effects of using semi-circular lateral corrugated stiffeners on the elastic behaviors of the CFRP cylindrical tubes subjected to quasi-static latitudinal impact. Based on suggested bending characteristics, analytical equations of elastic behaviors for the cylindrical tube equipped with a semi-circular lateral corrugated core have been derived. The equations are considered for the CFRP tubes stiffened with 4, 6, 8, and 12 semi-circular lateral corrugated waves. Obtained strain results conducted from low-velocity FEM analysis and impact experiments employing the GOM DIC software verified the derived equations with more than 82% accuracy. Additionally, it is found that the CFRP tube stiffened with a four-wave lateral corrugated core displays a positive impact failure of 74% compared to the non-stiffened tube.

Low-Velocity Impact Resistance of 3D Re-Entrant Honeycomb Sandwich Structures with CFRP Face Sheets

Lightweight sandwich structures have been receiving significant attention. By studying and imitating the structure of biomaterials, its application in the design of sandwich structures has also been found to be feasible. With inspiration from the arrangement of fish scales, a 3D re-entrant honeycomb was designed. In addition, a honeycomb stacking method is proposed. The resultant novel re-entrant honeycomb was utilized as the core of the sandwich structure in order to increase the impact resistance of the sandwich structure under impact loads. The honeycomb core is created using 3D printing. By using low-velocity impact experiments, the mechanical properties of the sandwich structure with Carbon-Fiber-Reinforced Polymer (CFRP) face sheets under different impact energies were studied. To further investigate the effect of the structural parameters on the structural, mechanical properties, a simulation model was developed. Simulation methods examined the effect of structural variables on peak contact force, contact time, and energy absorption. Compared to traditional re-entrant honeycomb, the impact resistance of the improved structure is more significant. Under the same impact energy, the upper face sheet of the re-entrant honeycomb sandwich structure sustains less damage and deformation. The improved structure reduces the upper face sheet damage depth by an average of 12% compared to the traditional structure. In addition, increasing the thickness of the face sheet will enhance the impact resistance of the sandwich panel, but an excessively thick face sheet may decrease the structure's energy absorption properties. Increasing the concave angle can effectively increase the energy absorption properties of the sandwich structure while preserving its original impact resistance. The research results show the advantages of the re-entrant honeycomb sandwich structure, which has certain significance for the study of the sandwich structure.

Research on Low-Velocity Impact Response of Novel Short-Fiber-Reinforced Composite Laminates

Short-fiber-reinforced polymers (SFRPs) based on unidirectionally arrayed chopped strands (UACSs) have excellent formability and outstanding mechanical response. The low-velocity impact response, such as the delamination, damage tolerance and energy absorption of UACS composites, are essential to guarantee the stability and safety of composite components in service. The current study investigates the low-velocity impact response of continuous carbon-fiber-reinforced polymer (CFRP) and UACS laminates with vertical slits under drop-weight impact with various impact energies (4, 7 and 11 J). The in-plane size of the studied samples is 100 mm × 100 mm, and the stacking sequence is [0/90]4s. The time-history curves of load and energy are examined during low-velocity impact experiments, as well as the nonvisible damages are obtained by ultrasound C-scan imaging technique. A user-defined subroutine VUMAT, including the Johnson-Cook material and failure model, which is used to simulate the elastic-plastic property of the slits filled with resin, is coded in ABAQUS/Explicit. According to C-scan inspections of the impact-damaged laminates, UACS specimens show more severe delamination as impact energy increases. The damaged area of continuous CFRP laminates under impact energy of 11 J is 311 mm2, while that of UACS laminates is 1230 mm2. The slits have a negative effect on the load-bearing capacity but increase the energy absorption of UACS laminates by approximately 80% compared to the continuous CFRP laminates at 7 J. According to the variables of different damage modes in numerical simulation, cracks appear at the slits and then expand along the direction perpendicular to the slits, leading to the fracture of fiber. Nevertheless, as the damage expands to the slits, the delamination confines the damage propagation. The existence of slits could guide the path of damage propagation.

Buckling and post-buckling characteristics of axially loaded channel-section CFRP/aluminum laminate profiles under the influence of impact damage

Damage caused by random impact incidents can greatly reduce the load bearing capacity of composite structural components. In this study, numerical simulations were performed to investigate the influence of impact damage on the buckling and post-buckling performance of carbon fiber reinforced polymer (CFRP)/aluminum laminate (CARALL) channel-section profiles. Low-velocity impact experiments and simulations were performed first on CARALL panel with the exact stacking configuration of the profiles to characterize the possible failure mechanisms for such hybrid components. Then, the dynamic responses of the channel-section profiles with the corner, web and flange impacted respectively, and the corresponding residual properties under axial compression were numerically revealed. Results showed that the residual deformation of specimens after impact was the dominate factor concerning its residual buckling load, and the post-buckling strength was mainly determined by the material damage propagation in the post-buckling stage. The specimens with corner impacted exhibited the highest residual axial buckling load and the lowest failure load compared with the ones with web or flange impacted. This work intended to provide insight into developing novel fiber reinforced polymer/metal hybrid structural components with high impact resistance.

On Quasi-Static and Dynamic Compressive Behaviors of Interlocked Composite Kagome Lattice Structures

Abstract The quasi-static and dynamic compressive behaviors of carbon fiber-reinforced plastic (CFRP) Kagome lattice structures subjected to quasi-static load and low-velocity impact were investigated experimentally and numerically. CFRP Kagome lattice structures were fabricated by using the interlocking method. The quasi-static compression and low-velocity impact experiments were carried out and the failure mechanisms of CFRP Kagome lattice structures were explored. A user-defined material subroutine (VUMAT) involving three-dimensional Hashin criterion and progressive damage evolution was developed and implemented in the refined finite element (FE) model to model the failure of composite lattice structures. Good agreement is achieved between FE simulations and experimental results. It is shown that both in-plane stiffness and the failure mode of CFRP Kagome lattice structure are sensitive to the load directions. CFRP Kagome lattice structures subjected to quasi-static load experience elastic deformation, bending/kinking failure, rib fracture, and structure collapse sequentially. CFRP Kagome lattice structures subjected to low-velocity impact suffer from the multiple fractures at the slots and the maximum peak loads of dynamic response increase with increasing the impact velocity.

Numerical Study of the Hygrothermal Effects on Low Velocity Impact Induced Indentation and Its Rebound in Composite Laminate

Impact indentation is believed to be an effective indication of low-velocity impact (LVI) damage for polymer matrix composites. However, it has been discovered that an indentation can partially rebound over time. Impact indentation and its rebound behavior over a period of time are significantly affected by hygrothermal conditions, especially moisture absorption. Therefore, a good understanding of the moisture-dependent impact indentation and its rebound behavior is helpful for impact damage assessment for composites. In this paper, moisture effects are considered for both the intra-laminar transverse property model and the interlaminar interface model in the simulation of impact indentation. Then, in these two models, viscosities are introduced to represent the indentation rebound over time. In order to validate the proposed models, LVI experiments with different impact energies were conducted on dry and hygrothermal conditioned carbon fiber/epoxy matrix composite laminates. For the specimens, the initial depths of impact dents and their rebounds over time were measured. The specimens of hygrothermal conditions were found with deeper dents compared with dry ones under the same impact energy; and their rebounds were also more significant. These phenomena were explained by the fact that moisture softens epoxy in composite and meanwhile elevates its viscosity. This indentation and its rebound phenomenon were simulated in ABAQUS by considering the moisture effects and viscoelasticity with user-defined material subroutines. These experiments were simulated using the proposed models, and the numerical predictions conformed well with the experimental observations.