Improving the energy absorption capabilities of carbon fiber/epoxy composites by embedding steel wire meshes

1 Introduction

Fiber-reinforced composites are replacing metallic parts because they meet the high mechanical performance and lightweight expected from structural parts [1], [2], [3], [4], [5]. Carbon fiber composites are favored in automotive, aviation, marine, sports, and construction industries for their low density, corrosion resistance, high strength and stiffness, and good resin bonding [6], [7], [8], [9]. In addition to these positive properties of carbon fibers, a handicap of its brittle structure is its weak resistance to impact loading [10], [11], [12]. In this sense, one of the most common and effective methods to improve toughness properties of carbon fibers is the hybridization with ductile fibers [13], [14], [15], [16], [17], [18]. Fiber/metal hybrids exploit the ductility and plasticity of metals to enhance the toughness and impact performance of brittle fiber composites [19], [20], [21]. However, due to the weakening of the adhesion on the fiber and metal surfaces caused by environmental effects over time, delamination between the fiber and metal may cause a decrease in energy absorption [22], [23]. Using cellular-structured wire meshes improves resin–fiber adhesion and enhances mechanical performance by minimizing negative effects [24], [25]. Adding metal wire meshes to fiber composites reduces delamination and fiber breakage through metal plastic deformation, enhancing energy absorption [26]. Steel, aluminum, brass and copper wire mesh materials are used in order to obtain high-performance structures in composite materials [27]. Steel wire meshes are widely used as secondary reinforcement in polymer composites for impact absorbing in automotive, aerospace, and defense applications due to having high ductility, yield strength, and energy absorption [28], [29], [30].

Researchers study the mechanical behavior of hybrid structures by manufacturing hybrid laminates with adding stainless steel wire meshes into various types of fiber-reinforced polymer matrix composites. Regarding this; Truong and Choi [23] examined the tensile strength of carbon fiber/steel wire mesh hybrid epoxy composites using different number of mesh layers and different mesh sizes. Wan et al. [24] found that embedding steel or aluminum wire mesh in carbon fiber/epoxy laminates spread impact loads and enhanced energy absorption Truong et al. [25] showed that steel wire mesh enhanced tensile strength, fracture stability, and durability of carbon fiber/epoxy composites, especially when fiber layers were few, by providing additional load-bearing capacity. Karunagaran et al. [26] carried out the low-velocity impact tests of glass fiber woven/steel wire mesh epoxy composites. Impact resistance improved with the addition of steel wire. Prakash and Jaisingh [31] reported that stainless steel wire mesh improved penetration resistance of glass fiber/epoxy composites compared to aluminum mesh. Wan et al. [32] reported that steel wire mesh improved the impact resistance of glass fiber/epoxy composites by enhancing load capacity and delamination. Sakthivel and Vijayakumar [33] found that steel wire mesh improved damage resistance in glass fiber/epoxy composites by enhancing mesh–matrix adhesion. Fayzulla et al. [34] produced steel wire mesh/glass and basalt fiber epoxy composites with varying mesh layers and evaluated their tensile, bending, and impact properties. Elumalai et al. [35] studied asna fiber/steel wire mesh epoxy composites for automotive bumpers and found that steel wire reduced tensile and bending strength but improved impact resistance, surpassing both non-wire composites and steel structures. Loganathan et al. [36] reported that aligning stainless steel wire mesh with banana fiber orientations in epoxy composites enhanced strength and energy absorption, as microscopic analysis showed improved load transfer through varied damage mechanisms. Singh and Rajamurugan [37] showed that adding steel wire mesh to hemp- and flax-reinforced vinylester and epoxy composites improved mechanical performance by enabling plastic deformation and strong matrix adhesion, preventing brittle fracture. Uzay and Geren [38] found that adding steel wire mesh to carbon fiber/foam sandwich structures increased load capacity and reduced bending damage. Hasselbruch et al. [39] reported that steel wire mesh in PPS–carbon fiber composites improved tensile behavior by enabling controlled deformation and limiting crack propagation.

The mechanical behavior of steel wire meshes in polymer composites has been widely studied for their ability to enhance structural performance. Key factors such as wire diameter, thickness, and mesh size influence strength, stiffness, and energy absorption. This study focuses on the energy absorption and damage mechanisms of carbon fiber/stainless steel wire mesh epoxy composites under low-velocity impact, examining how the number and placement of wire mesh layers affect peak impact force and overall energy absorption.

2 Materials and experimental studies

Reinforcement elements are consisted of woven carbon fibers with an area density of 200 g m⁻² and 30 mesh size stainless steel (AISI 304 SSWM) wire meshes with a wire diameter of 0.30 mm. Sika CR-80 epoxy resin and Sika CH 80-2 epoxy hardener were chosen as matrix materials. Figure 1 shows the manufacturing process of the composite laminates. Composites were produced according to the vacuum infusion method. After the composites were kept under vacuum for 24 h, they were subjected to 60 °C in the oven for 4 h for post curing. Composite plates were then cut to 100 mm × 100 mm dimensions for the low-velocity impact tests. Low-velocity impact tests were performed with an Instron falling weight impact tester. Figure 2 shows the impact testing machine. The striker weight is 5.5 kg and the striker diameter is 20 mm. 20, 30 and 40 J impact energies were applied to the composites. Table 1 shows the properties of the composite laminates.

Figure 1:

Manufacturing process of the composite laminates. a) Carbon fiber woven and steel wire mesh, b) lay-up sequences of the composites, c) manufacturing of the laminates.

Figure 2:

Impact testing machine.

3 Results and discussion

Figures 3 and 4 present the force–displacement and force–time responses of the composite specimens under various impact energy levels. Generally, the lowest maximum force and impact strength are observed in this example at all three energy levels in C₈ composites. This structure exhibits brittle behavior and rapid energy loss occurs because crack propagation is not prevented by the wire mesh. C₂/S/C₆ which is the single layer wire mesh, the increase in force is significant compared to C₈. The steel wire mesh provides a more ductile behavior by dissipating energy. However, since the wire mesh is located in only a single region, the impact energy distribution is limited. However, C₂/S/C₂/S/C₄ which is the two-layer wire mesh, In interlayer composites, a more balanced and high force carrying capacity is occurred with this structure. Placing the wire mesh in the intermediate layers prevents crack propagation more effectively. This structure offers a more optimized response in terms of ductility. On the other hand, C₂/S/C₂/S/C₂/S/C₂ which is the multilayer wire meshed, the highest maximum force at all energy levels is observed in this structure. As the number of wire mesh increases, the load carrying capacity increases and the displacement occurs in a more controlled manner. Especially in the 30 J and 40 J graphs, this structure absorbs energy with both high force and less deformation. As the number of meshes increases and the meshes are distributed homogeneously, the composite structure can withstand higher forces and absorb more energy. Wire meshes delay sudden fracture after impact by stopping crack propagation. Placing wire mesh in intermediate layers controls both upper surface damage and crack propagation on the lower surface. Multi-layer wire mesh reinforcement significantly increases performance as the impact energy increases, indicating that steel wire meshes are critical not only in terms of strength but also energy absorption. The energy level increases, displacement increases, maximum force cannot exceed a certain value in the no wire mesh C₈ composite. As this structure shows that it is quite weak against impact.

Figure 3:

Force-displacement curves of the composites.

Figure 4:

Force-time curves of the composites.

As seen in the curves, in the single-layer wire mesh C₂/S/C₆, although it provides some improvement, deformation is still high; cracks are limitedly controlled by wire mesh. In the double mesh in intermediate layers C₂/S/C₂/S/C₄, force is better distributed and sudden fractures are reduced. A good balance has been established between energy absorption and rigidity. In the multi-layer wire mesh C₂/S/C₂/S/C₂/S/C₂, even if the impact energy increases, the displacement remains more controlled, the structures maintain their integrity and energy is absorbed. This structure stands out as the most optimum structure in terms of both strength and ductility.

Figure 5 shows the energy-time curves of the composites. These curves show the energy accumulated over time during impact phenomena applied to composites at different impact energy levels. The energy-time curves obtained from low-velocity impact tests reveal critical insights into the mechanical response and damage behavior of the composite specimens. Generally, it is seen that in the initial region of the curves, the energy increase is linear for all specimens, reflecting the elastic response of the system, with similar slopes indicating comparable initial stiffness across configurations. The subsequent plateau or drop in the curve marks the onset of damage mechanisms such as matrix cracking, fiber breakage, or delamination, where the energy absorption rate decreases [40], [41], [42]. The peak point on the curve corresponds to the maximum absorbed energy and serves as an indicator of the specimen’s impact toughness [43]. Once the curve stabilizes, it suggests that no additional energy is being absorbed, indicating either the completion of internal damage mechanisms or the occurrence of penetration. Under 20 J impact energy, hybrid specimens continued to outperform the reference. At 30 J, the same configuration again recorded the highest energy absorption, confirming the effectiveness of multiple steel mesh layers C₂/S/C₂/S/C₂/S/C₂ in dissipating impact forces and arresting crack propagation. Conversely, specimens like C₂/S/C₆ and C₂/S/C₂/S/C₄ reached a plateau more quickly, indicating rapid energy uptake possibly accompanied by localized damage. At 40 J, all configurations managed to absorb the majority of the impact energy, with C₂/S/C₂/S/C₄ design achieving the highest energy absorption at penetration limit. The rate of energy absorption prior to stabilization and the duration of the plateau phase reflects the specimen’s resistance to impact-induced damage and its ability to sustain deformation over time. It is seen that the contribution of steel mesh layers, particularly when placed near the outer surfaces, proved crucial in resisting the initial impact, while intermediate layers contributed more to energy dissipation and damage dispersion.

Figure 5:

Energy–time curves of the composites.

The velocity–time curves shown in Figure 6 were analyzed to evaluate the dynamic responses of the composite samples under low-velocity impact. These curves provide important information about the output velocity of energy dissipation by showing the change of velocity after impact with respect to time. The C₈ sample exhibited a trend in which the velocity decreased more slowly at each impact energy level and reached zero late. This situation shows that the composite structure could not absorb the impact energy sufficiently and the structural deformation was largely irreversible. The asymmetric course of the velocity curve indicates that the system developed permanent damage by going beyond its elastic limits. The C₂/S/C₆ configuration exhibited a behavior in which the velocity decrease occurred in a shorter time after impact, but complete dissipating could not be provided at high energies. The fact that the wire mesh structure was limited to a single layer caused the energy to be concentrated in certain regions and therefore the velocity to stabilize before reaching zero. This shows that although the energy absorption capacity has partially increased, the deformation has not been fully controlled. The C₂/S/C₂/S/C₄ configuration, which contains wire mesh in two intermediate layers, presented a profile in which the velocity decreased more sharply and reset earlier after the impact. This structure provided a more controlled distribution of energy; thus, the sudden decreases in velocity revealed that the damage developed in a more controlled manner and the rebound movement was limited. The highest performance was observed in the C₂/S/C₂/S/C₂/S/C₂ configuration. This sample produced a graph in which the velocity reached zero in the shortest time after the impact and remained stable at a level close to zero. This situation shows that multilayer wire meshes are extremely effective in dissipating the impact energy and in resisting the sudden deformation of the structure. This feature of the velocity–time curve reveals that the energy is absorbed widely among the structural components and the damage remains localized. In general, both the increase in the number of wire mesh layers and their symmetrical placement in the interlayers ensured that the velocity was reset earlier. This shows that the composites provided a significant increase not only in mechanical strength but also in energy absorption ability in terms of impact resistance.

Figure 6:

Energy–time and velocity–time curves of the composites.

Figure 7 shows the velocity–displacement responses of the composites. Generally, maximum displacement of all structures increases when going from 20 J to 40 J, which naturally indicates that more deformation occurs with higher energy. At 20 J, the response curves of all specimens display relatively symmetric shapes with low maximum displacement values, indicative of primarily elastic deformation and limited internal damage. These closed curves show the rebound phenomena of the striker on the specimen surface [32]. However, as impact energy increases, notable divergences emerge between the configurations. Especially at 30 J and 40 J the curves become asymmetric. This could mean that the structure is permanently deformed or does not exhibit fully elastic behavior. The C₈ laminate, consistently registers the highest peak displacements across all energy levels. This behavior is attributed to its high capacity to absorb energy but low recovery. As the increase of impact energy, the extended curve profiles and slower deceleration suggest limited internal damping and a tendency toward pronounced structural deformation or delayed recovery. Hybrid configurations incorporating stainless steel mesh interlayers exhibit markedly different behavior by demonstrating improved damping characteristics and reduced displacement. This shows that they behave more efficiently in terms of energy absorption and dissipation, dissipating energy with less displacement. The presence of stainless-steel mesh likely plays a significant role in enhancing energy absorption by promoting progressive damage mechanisms, such as fiber-matrix debonding, delamination, and interlayer sliding, without catastrophic structural failure such as 20 J and 30 J impact energies as seen in Figures 8 and 9. The C₂/S/C₂/S/C₄ configuration shows more confined curves with quicker deceleration trends, implying a more efficient energy conversion process and lower residual motion. The intermediate steel layers not only increase resistance to crack propagation but also provide distributed reinforcement, enhancing structural resilience. The C₂/S/C₂/S/C₂/S/C₂ laminate exhibits the most favorable impact behavior, particularly at higher energy levels. With three stainless steel mesh interfaces evenly spaced between four carbon fiber sub-laminates, this structure displays the smallest displacements and fastest return to zero velocity. These features indicate superior energy dissipation capacity, most likely due to the increased number of interfaces which facilitate gradual energy absorption and restrict the extent of damage propagation.

Figure 7:

Velocity–displacement curves of the composites.

Figure 8:

Damage mechanisms of the composites.

Figure 9:

Cross sectional view of the damage mechanisms of the composites.

Figure 8 shows the damage mechanisms of the composites. It is seen that the damages in composites consisting only of carbon fiber develops with different mechanisms depending on the impact energy. At the impact energy of 20 J, it was observed that fiber fractures began on the front and back surfaces. At this stage, both the matrix and the carbon fibers were damaged, and structural integrity was weakened. At a high impact energy of 30 J, serious fiber fractures occurred on both the front and back surfaces, and complete perforation occurred. This shows that the capacity of the composite structure to absorb the impact energy was completely exceeded, and all layers broke, and the load bearing capacity of the composites completely lost.

In C₂/S/C₆ composites at 20 J, matrix cracking was still predominant on the front surface; however, fractures began to appear on the rear face. The initiation of fiber fracture indicates that although the steel mesh aids in energy absorption and stress redistribution, increasing impact energy exceeds the matrix’s capacity, leading to localized fiber failure particularly at the back surface where tensile stresses are maximized. At 30 J, more severe matrix cracking accompanied by distinct fiber fractures were observed on both surfaces. Addition of steel wire mesh appears to delay but not completely prevent the onset of catastrophic damage. The combination of matrix cracking and fiber fracture at this stage indicates a complex failure mechanism involving fiber/matrix debonding, matrix shear cracking, and fiber pull-out, highlighting the transition from matrix-dominated damage to fiber-dominated failure. At 40 J, full perforation was evident, characterized by a relatively symmetric and contained damage area. The regularity of the perforation layers suggests that the steel wire mesh not only contributes to delaying the perforation but also influences the manner in which damage propagates through the laminate, promoting a more uniform and predictable failure pattern.

In C₂/S/C₂/S/C₄ composites at an impact energy of 20 J, matrix cracking became more pronounced, with larger and more defined cracked areas. However, the absence of fracture at this energy level suggests that the two layered steel mesh architecture in the laminate continued to distribute the impact load effectively, delaying fiber damage by promoting energy dissipation mainly through the matrix. At 30 J, localized fracture began to occur alongside the existing matrix cracking. This indicates that the energy level was sufficient to overcome the load-bearing capacity of the carbon fibers at specific locations, despite the toughening contribution of the intermediate steel meshes. The occurrence of fiber breakage at this stage highlights a transition from matrix-dominated damage towards combined matrix and fiber failure mechanisms. At 40 J, fiber fracture became the dominant damage mode, visible on both the front and back surfaces. Nevertheless, the damage areas appeared relatively contained, suggesting that the multi-mesh configuration successfully restricted crack growth and fiber rupture to a localized region, thus preventing catastrophic structural failure.

In C₂/S/C₂/S/C₂/S/C₂ composites at 20 J impact energy, mainly matrix cracks and local dents on the surface occurred in the samples, and fiber breakage was not observed. In addition, bulging and dome formation on the back surface were seen, indicating that the energy was transmitted to the back surface in a localized manner. At the 30 J energy level, both matrix cracks and fractures began to be observed, indicating that the composite was approaching the limits of its energy absorption capacity. At the 40 J level, fracture lines became more widespread, and matrix cracks progressed more clearly. In general, steel wire meshes significantly improved the brittle characteristics of carbon fiber reinforced composites by contributing to the localization of damage at contact regions.

Figure 9 shows the cross-sectional view of the damage mechanisms of the composites. At medium energy levels (30 J), the damage magnitude increased; fracture, larger matrix cracking and interlayer delamination became apparent. At high impact energies (40 J), fiber rupture, severe matrix cracking and widespread delamination caused serious structural deterioration throughout the section. When the damage typology was examined, it was understood that in addition to intense fiber breakage in the central region, secondary damage mechanisms such as collapse and fiber bundle shifting also developed. In this context, it has been observed that steel mesh layers provide an effective energy absorption mechanism by reducing fracture and matrix cracking.

Table 2 shows the summary of the impact characteristics of the composites. The relationship between the peak force and total displacement of composites with the increase in impact energy shows the changes in the energy absorption capacity and deformation behavior of the material. While the C₈ composite shows the lowest peak force values at all energy levels, the peak force values of hybrid composites also increase depending on the number of steel wire meshes. Steel wire improves the energy distribution in the internal structure of the composite material and helps to spread local stress accumulations at the moment of impact. In this way, more steel wire layers allow the impact energy to be absorbed in a wider area and the displacements to be directed in a more controlled manner. This mechanism ensures that the peak force increases as the number of steel wires increases. As seen in Table 2, the increase in impact energy causes the force and deformation to which the material is exposed to increase. As the impact energy increases, the peak force also increases. This can be explained by the fact that the composites exceed their elastic limits and enter plasticity. Plasticity increases the deformation capacity of the material, which results in higher peak forces. However, at high energies, the material absorbs more energy and encounters more force, which limits the material’s load carrying capacity. During this process, some materials may undergo structural deterioration such as cracking, fiber breakage, penetration or perforation. For example, while fail is observed in C₈ and C₂/S/C₆ samples at 30 J and 40 J impact energies, hybrid structures such as C₂/S/C₂/S/C₄ and C₂/S/C₂/S/C₂/S/C₂ are more resistant to these energies. The ability of these structures to spread the energy over a wider area prevents local stress accumulation under impact and delays the fracture or delamination of the material. This mechanism allows hybrid composites to perform better against high energies. In low-velocity impact tests, the total displacement of target materials increases with the increase in impact energy. As the impact energy increases, the spread of the energy over a larger area causes larger deformations and increased displacement [44], [45]. The increased energy leads to plasticity by exceeding the elastic limit of the material, causing larger deformations due to the low hardness of the matrix materials. In addition, delamination may develop under the effect of the impact energy, which weakens the bearing capacity and increases the displacement [46]. Increasing energy reduce the bearing capacity of the material by triggering microstructural deterioration and crack formation [47], [48]. According to Table 2, pure carbon fiber/epoxy composites (C₈) exhibited relatively high deformation with increasing impact energy the deformation increased strongly and perforation occurred as a result. This behavior indicates that the elastic deformation capacity of pure carbon fiber composites is low and brittle failure modes such as matrix cracking and fiber fracture come into play early. Hybrid configurations exhibited a significant improvement in deformation behavior. The C₂/S/C₆ structure containing a single layer of steel wire mesh limited the deformation to a certain extent (7.61 mm at 20 J), but at high impact energies (after 30 J), it exceeded its plasticity capacity and underwent perforation. The C₂/S/C₂/S/C₄ configuration containing two layers of steel wire mesh further reduced the deformation at 20 J impact (5.79 mm), thus distributing the impact load to a larger area and reducing the stress concentrations on the matrix and fiber systems. The highest performance was obtained with the C₂/S/C₂/S/C₂/S/C₂ multilayer hybrid structure, which exhibited low deformation even at high impact energies (5.63 mm at 30 J and 8.01 mm at 40 J), maximizing both elastic deformation capacity and plastic deformation resistance. Multi-layer steel wire mesh effectively dissipated the local stress concentrations generated during impact, limited the crack propagation, and delayed the rupture of the fiber/matrix interface, thus maintaining the load-carrying capacity.

Figures 10 and 11 show the damage indexes and specific absorbed energy values versus impact energy of the composites, respectively. Pure carbon fiber composites (C₈) exhibited a brittle behavior by exhibiting a high degree of damage even at low impact energies. Hybrid structures with added steel wire mesh layers increased the load carrying capacity during impact and provided a more controlled spread of damage. Especially composites with multilayer structure (C₂/S/C₂/S/C₂/S/C₂) reached the highest peak force and absorbed a large portion of the impact energy, while also preserving the structural integrity by keeping the deformation limited. The high energy absorption of pure carbon fiber composites (C₈) jeopardizes their structural integrity as it reveals damage mechanisms such as, fiber breakage, delamination and perforation as seen in damage surfaces in Figures 8 and 9. Therefore, it shows that pure carbon fiber composites’ resistance to impact is weak. Similarly, the specific energy absorption (SEA) shows the same tendency. When the damage degree of the composites was examined, it was observed that the steel wire meshes, as seen from the damage surface images, prevented sudden fractures by limiting the matrix cracking and stopping the crack propagation. Damage is evaluated in references [41], [42], [48] by how much of the impact energy is absorbed by the specimen as in Equation (1).

with E_impact: Total energy applied in the impact, E_absorbed: Energy absorbed by the sample.

Figure 10:

Damage index of the composites.

Figure 11:

Specific absorbed energy versus impact energy of the composites.

D_i = 0 shows the do damage occurred and energy is completely rebounded, D_i = 1 shows that all energy is absorbed and severe damage occurred. The situation where the impactor tip completely penetrates the sample. The sample absorbs almost all of the energy. Pure carbon fiber composites were completely punctured, especially at high impact energies, the damage in multilayer hybrid structures was absorbed by spreading with the plastic yielding in the wire mesh and a more balanced fracture behavior was exhibited by preventing fiber fractures and keeping delamination limited.

4 Conclusions

In this study, carbon fiber/steel wire mesh hybrid composites were manufactured and the effects of fiber sequences on bending and impact properties were examined. The following results were obtained:

The experimental findings underscore the critical role of layup architecture in governing the impact performance of laminated composite materials. The integration of stainless-steel wire meshes into carbon fiber/epoxy composites significantly enhances their resistance to low-velocity impacts by improving energy absorption capacity and mitigating brittle fracture behavior. While pure carbon laminates inherently possess high stiffness and lightweight characteristics, they exhibit limited toughness and are prone to severe matrix cracking, delamination, and fiber breakage under dynamic loading conditions. In contrast, the hybridization with ductile steel mesh layers introduces additional energy-dissipating mechanisms such as plastic deformation and frictional interlocking which promote progressive damage evolution rather than sudden catastrophic failure. Analysis of energy–time and velocity–time response curves reveals that multilayer mesh-reinforced configurations enable faster energy damping, reduced rebound, and more controlled structural deformation. Among all tested lay-up sequences, the C₂/S/C₂/S/C₂/S/C₂ configuration consistently demonstrated the highest peak impact forces and lowest displacement values, indicating enhanced damage tolerance, better crack arresting capability, and superior structural integrity. These features render multilayer hybrid composites highly promising for applications demanding both high impact resistance and mechanical reliability, such as in aerospace, defense, and automotive crash-critical structures.