Advances in Toughening Modifications of Carbon Fiber/Epoxy Resin Composites: A Comprehensive Review

Carbon fiber-reinforced epoxy resin composites (CFRP) have revolutionized industries such as aerospace, automotive, wind energy, and marine engineering due to their exceptional strength-to-weight ratio, high stiffness, and corrosion resistance. However, the inherent brittleness of epoxy resins—a consequence of their highly crosslinked network structure—poses significant limitations, particularly in applications requiring impact resistance or fatigue durability. Addressing this challenge, researchers worldwide have explored innovative strategies to enhance the toughness of CFRP without compromising its mechanical properties. This article provides an in-depth review of recent advancements in toughening modifications, focusing on resin matrix optimization, interfacial engineering, structural design, and emerging technologies.

1. Current Status of Toughening Modifications

1.1 Resin Matrix Modification

The toughness of epoxy resins can be significantly improved by incorporating secondary phases or modifying their molecular structure. Key approaches include:

• Nanostructured Materials:
  Nanoparticles (e.g., carbon nanotubes, graphene, and metal oxides) have emerged as promising additives due to their high surface area and ability to disrupt crack propagation. For instance, Dong et al. demonstrated that adding 0.5 wt% multi-walled carbon nanotubes (MWCNTs) to epoxy increased the Mode II fracture energy of CFRP by 71%, while Shi et al. showed that nano-MgO particles enhanced impact strength compared to microscale MgO. These nanoparticles act as stress concentrators, promoting microcrack nucleation and energy dissipation.
• Thermoplastic Polymers:
  Blending thermoplastics (e.g., polyetheretherketone, PEEK; polycarbonate, PC) with epoxy creates a dual-phase morphology that arrests crack growth. Yao et al. reported a 157% increase in interlaminar fracture toughness (G₁C) using thin PEEK films as interlayers, though excessive curing times weakened this effect. Wu et al. introduced an in situ polymerizable thermoplastic toughener (PTS) via click chemistry, achieving superior phase separation and toughness enhancement without compromising thermal stability.
• Rubber Toughening:
  Reactive liquid rubbers like carboxyl-terminated butadiene acrylonitrile (CTBN) have long been used to create a phase-separated morphology. Zhao et al. optimized CTBN content (6.9 wt%) in AG-80 epoxy, balancing toughness and fiber-matrix adhesion. Xu et al. further enhanced compatibility through in situ crosslinking, improving both mechanical properties and interfacial bonding.
• Block Copolymers:
  Block copolymers (BCPs) offer precise control over nanoscale morphology. Xi et al. synthesized amphiphilic AA-PPA copolymers that induced ductile fracture in brittle epoxy, while Chen et al. achieved hydrogen-bond-driven synergistic toughening with biobased PPA2000, maintaining tensile strength at 59.25 MPa even at high loadings.

1.2 Interfacial Engineering

The fiber-matrix interface governs stress transfer efficiency. Strategies to optimize interfacial adhesion include:

• Plasma Treatment:
  Plasma irradiation modifies CF surfaces by introducing polar functional groups (e.g., hydroxyl, carboxyl). Zhang et al. achieved a 30% increase in interfacial shear strength (IFSS) via argon plasma treatment combined with maleic anhydride grafting, while Yuan et al. employed microwave-induced microplasmas to deposit graphene oxide (GO), enhancing surface roughness and wettability.
• Oxidative Treatments:
  Electrochemical oxidation followed by electrophoretic deposition of GO onto CF surfaces improved composite interlaminar shear strength by 59.4% (Jiang et al.). This method preserves fiber strength while creating a robust interphase layer.
• Coating and Grafting:
  Applying phenolic resin coatings (He et al.) or integrating MWNTs onto CF surfaces (Liu et al.) creates a hierarchical interface that combines chemical bonding and mechanical interlocking. Chemical grafting of branched polyethyleneimine (PEI) onto CFs further boosted IFSS to 107.2 MPa via dense amine-functionalization (Tang et al.).

1.3 Structural Design Innovations

Macroscopic structural optimization complements material-level modifications:

• Interleaved Structures:
  Inserting thin films (e.g., PEEK, rubber) between CFRP layers disrupts crack propagation. Interleaves can increase G₁C by over 100% while maintaining in-plane properties (Yao et al.).
• Hybrid Composites:
  Combining carbon fibers with other reinforcements (e.g., glass fibers, nanofillers) creates heterogeneous stress distribution networks. For example, hybrid CF/glass fiber laminates exhibit improved impact resistance compared to single-fiber systems.
• 3D Architectures:
  Three-dimensional woven or braided composites reduce delamination risks by interlocking fibers in multiple directions, enhancing through-thickness toughness.

2. Key Challenges and Limitations

Despite progress, several challenges persist:

• Performance Trade-offs: Toughening agents like rubbers often reduce modulus or thermal stability. Balancing toughness with other mechanical properties remains elusive.
• Interfacial Complexity: Optimizing adhesion across diverse fiber/matrix combinations (e.g., different CF surface treatments) lacks universality.
• Mechanistic Gaps: The synergistic effects of multi-component systems (e.g., nanoparticles + thermoplastics) are poorly understood.
• Environmental Durability: Long-term stability under harsh conditions (humidity, temperature cycling) is critical for real-world applications but remains underinvestigated.

3. Future Directions

To overcome these challenges, future research should focus on:

3.1 Multiscale Synergistic Toughening

• Nano-Micro Hybrid Systems: Combine high-surface-area nanomaterials (e.g., graphene) with microscale tougheners (e.g., rubber particles) to create hierarchical energy-dissipation networks.
• Biomimetic Design: Mimic natural structures like nacre’s brick-and-mortar arrangement or bone’s osteon architecture to optimize interface mechanics and damage tolerance.

3.2 Sustainable and Green Approaches

• Bio-Based Tougheners: Develop renewable polymers (e.g., cellulose derivatives, chitosan) as eco-friendly alternatives to petroleum-derived additives.
• Solvent-Free Processes: Replace traditional solution blending with melt compounding or in situ polymerization to reduce environmental footprints.

3.3 Intelligent and Multifunctional Materials

• Self-Healing Composites: Integrate dynamic covalent bonds (e.g., Diels-Alder reactions) or microencapsulated healing agents to enable autonomous crack repair.
• Multifunctional Integration: Engineer composites that combine toughness with conductivity (carbon nanotubes), thermal management (BN nanosheets), or sensing capabilities (piezoelectric fillers).

3.4 Advanced Characterization and Simulation

• In Situ Techniques: Use atomic force microscopy (AFM), digital image correlation (DIC), and synchrotron X-ray imaging to visualize crack propagation dynamics.
• Machine Learning: Deploy AI algorithms to predict optimal toughener combinations and processing parameters, accelerating material discovery.

3.5 Scalability and Industrialization

• Cost-Effective Manufacturing: Develop continuous fiber-reinforcement processes (e.g., pultrusion, automated fiber placement) compatible with toughened resins.
• Standardization: Establish standardized testing protocols for toughness metrics (e.g., G₁C, J-integral) to facilitate industrial adoption.

4. Hot Research Topics

Several emerging areas show significant promise:

• Graphene/Carbon Nanotube Hybrids: Synergistically combining 2D graphene and 1D CNTs to form conductive, tough interphases.
• Dynamic Crosslinking Epoxies: Designing epoxy networks with reversible bonds (e.g., boronic esters) for self-healing and reprocessability.
• Additive Manufacturing (AM): Tailoring graded toughening architectures via 3D printing for complex components.
• AI-Driven Material Design: Using machine learning to predict optimal toughener compositions and processing conditions.

Carbon fiber reinforced polymer (CFRP) has been widely used in aerospace, automotive, marine and wind energy due to its excellent properties such as high strength, high rigidity and low density. However, the inherent brittleness of epoxy matrices limits the wide range of applications for CFRP. Therefore, how to improve its resilience has become a hot topic of research. This paper reviews the research progress of toughening and modification of carbon fiber/epoxy resin matrix composites in recent years, focuses on resin modification, interface modification and structural design, and looks forward to the future research directions.

For decades, carbon fiber-reinforced thermoset matrix composites have been widely used as structural materials in the aerospace, automotive, and marine industries due to their excellent specific mechanical properties. Thermoset epoxy resins are widely used as matrices for carbon fiber reinforced plastics (CFRP) due to their good mechanical properties and high heat resistance. However, epoxy matrices are inherently brittle due to their highly cross-linked network structure, which results in poor fracture toughness and limits their engineering applications in high-performance demanding industries. In addition, due to the anisotropy of unidirectional CFRP, the weaker out-of-plane mechanical properties result in lower impact resistance. These weaknesses can lead to eventual failures during service and the limitations they apply. Good interfacial bonding ensures payload transfer from the matrix to the fiber, which helps to reduce stress concentrations and improve overall mechanical properties. Since the nature of the interphase area in the matrix close to the surface of the fiber is different from that of the matrix, enhancing the structural integrity of the composite material allows for better stress transfer between the matrix and the fiber.

At present, the overall mechanical properties of CFRP composites are usually enhanced by three methods: matrix modification, CF surface treatment, and structural design. The focus of resin matrix modification is to enhance the toughness of the epoxy by incorporating high-toughness substances such as elastomers (rubber), thermoplastic resins, or rigid particles into the resin system as a binary phase, and by introducing “flexible molecular segments” into the epoxy resin. CF surface treatment methods include air oxidation, chemical grafting, physical deposition, irradiation, liquid phase oxidation, surface coating, and multi-scale modification. Structural design includes staggered structural design and sandwich structure design.

 1. Epoxy resin toughening and modification

1.1 Nanomaterial modified epoxy resin

In recent years, nanomaterials (NMs) have played an active role in various fields due to their nanoscale properties. The active groups on the surface of NMs can interact with epoxy resin to form a good interface between NMs and epoxy resin. External forces transfer the nanoparticles to their surroundings and cause microcracks in the epoxy matrix, which absorb energy to toughen the epoxy matrix. On the other hand, nanoparticles can be seen as physical cross-linking joints of molecular chains to hinder the propagation of microcracks.

Dong et al.7 added multi-walled carbon nanotubes (MWCNTs) to epoxy resins to improve the fracture toughness of bulk epoxy resins, and also used them as matrices for carbon fiber reinforced epoxy composites (CFRP). The addition of MWCNTs to bulk epoxy resin and CFRPs moderately increased the type I fracture energy, and significantly increased the type II fracture energy, and the average type II fracture energy of CFRPs increased from 2026 J/m² to 3406 J/m² after the addition of 0.5 wt% MWCNTs. Shi et al. systematically studied the effect of micro-nanoscale magnesium oxide (MgO) particles on the mechanical properties of carbon fiber/epoxy resin composites by adding various amounts of MgO particles to the epoxy resin matrix. It was found that the carbon fiber/epoxy resin composites filled with nano-MgO particles had higher mechanical strength than the carbon fiber/epoxy resin composites filled with micro-magnesium oxide particles. By adding the appropriate amount of nano-MgO particles, the impact strength and flexural strength can be enhanced.

1.2 Thermoplastic resin modified epoxy resin

The addition of thermoplastic resins (TPs) to CFRP is a common way to improve fracture toughness and impact resistance, which can improve the fracture toughness of epoxy resins without reducing thermal properties or elastic modulus. The duplex structure formed by the separation of thermoplastic resin and epoxy resin is the main toughening mechanism of thermoplastic resin interlacing in epoxy-matrix composites. For example, polyetheretherketone (PEEK) and polycarbonate (PC) can be mixed with epoxy resin by melt blending or solution blending method to improve the toughness of materials.

Yao et al. blended thermoplastic resin PEK-C with epoxy resin or prepared as an intermediate layer in the form of particles and films to enhance fracture toughness, and the interlaminar fracture toughness (G) of PEK-C film and mode I increased by 157.2% at a film thickness of 10 μm. By using PEK-C film as the interlayer, the interlaminar fracture toughness of CFRP was improved. The average G₁ curing time increased by 61.77%, 90.65%, 50.58% and 9.37% at 0.5h, 1h, 2h and 3h, respectively. The increase in curing time weakens the toughening effect of PEK-C films. Wu et al. developed a novel in-situ thermoplastic toughener, polytriazolone type polymer (PTS), which can be used as monomers to maintain the viscosity of epoxy resins and polymerize by azide-alkyne click reaction during epoxy resin curing. This new toughener can successfully improve the fracture toughness of epoxy or carbon fiber/epoxy composites.

Although significant progress has been made in thermoplastics, the strengthening of EP by TP remains a challenge. The optimal toughness improvement of TPs toughened epoxy resin system is achieved by obtaining co-continuous or inverted morphologies. For better toughening, TP with excellent thermal stability should be soluble in uncured epoxy resins. The phases must be separated during the curing process to form a multiphase morphology. In addition, the toughened system must be fully cured to minimize structural weaknesses introduced by unreactive functional groups.

1.3 Rubber elastomer modified epoxy resin

Toughening EP with rubber is one of the traditional methods in heterogeneous toughening systems. The addition of liquid rubber inhibits crack propagation in thermoplastic materials. In general, rubber toughened EP can be divided into reactive liquid rubber and rubber particles. A number of methods have been developed to toughen epoxy resins, among which the incorporation of liquid rubbers, such as butadiene acrylonitrile copolymer, hydroxyl terminated polybutadiene (HTPB), and natural rubber, appears to be the most successful. It is well known that two materials with similar solubility parameters should be compatible with each other. Functionalization can increase the cohesion of functionalized rubber, which increases the solubility parameter and thus the compatibility between epoxy resin and rubber.

Zhao et al. prepared a high-toughness epoxy resin using carboxy-terminated butadiallacrylonitrile (CTBN) as a toughening agent, and modified AG-80 epoxy resin. The mechanical properties, surface properties, tensile properties and fracture morphology of the composites were systematically studied, and the key factors affecting the interfacial bonding of high-performance CF/EP composites were clarified. The results showed that when the CTBN content in the epoxy resin was 6.90wt.%, the toughness was improved most significantly. Due to the high content of polar functional groups and excellent surface wettability of T800SC, T800SC/EP composites exhibit excellent mechanical properties compared to T800HB/EP composites. Xu et al. prepared an in-situ pre-crosslinked CTBN/epoxy resin blend, which had better mechanical properties than the traditional CTBN modified blend. A local interpenetrating structure was formed in the pre-crosslinked CTBN/epoxy resin blend, which greatly improved the compatibility and interfacial adhesion between the two phases, so that the blend had good mechanical properties. However, the rubber used has a high acrylonitrile content (25%) and is therefore miscible with epoxy resins.

1.4 Block copolymer modified epoxy resin

Unlike other toughened materials, the molecular structure of block copolymers (BCPs) can be easily manipulated to create spherical, rod-like, lamellar, and other separated phase morphologies at the nanoscale. Both non-reactive and reactive block copolymers can be added to epoxy resins to improve toughness. Non-reactive BCPs can form different nanostructures, such as bilayer vesicles, helminths, and spherical micelles, through self-assembly or reaction-induced phase separation, resulting in different toughening effects. Reactive BCPs can react with or cross-link epoxy resins. In this case, the covalent bonding of the block copolymer inclusions to the epoxy provides an opportunity to maximize the fracture toughness. The main copolymers studied include amphiphilic and chemically modified diblock or triblock copolymers as epoxy toughening agents.

Xi et al. synthesized a series of adipic acid-polyoxypropylene amine copolymers (AA-PPA), in which polyoxypropylene diamine (PPA D400) and adipic acid (AA) were arranged in an orderly manner. AA-PPAw=10400 and Mn=7600 with M were used to toughen DGEBA epoxy/DDM systems. By changing the amount of AA-PPA, the fracture and impact resistance of the cured epoxy resin from brittle fracture to ductile fracture are enhanced. Mechanical properties, including elongation at break and impact strength, were significantly improved. Chen et al. modified epoxy resin by using a PPA2000 prepared by the chain extension reaction of bio-based polyoxypropylene diamine D400 and adipic acid. The results showed that the PPA2000 content was as high as 25.3wt%, and the tensile strength still reached 59.25Mpa. In conclusion, the new intermolecular hydrogen bonds formed between PPA2000 resin and epoxy resin bring significant advantages to composites in terms of simultaneous strength and fracture toughness.

 2 Carbon fiber surface modification
The interfacial adhesion between the carbon fiber and the polymer matrix plays a crucial role in controlling the overall performance of the composite. Strong interfacial adhesion is known to increase the structural integrity of composites and efficiently transfer stress from the fibers to the matrix. However, the smooth and inert nature of the carbon fiber surface often results in poor wettability and adhesion between the fiber and the matrix, which hinders the advantages of carbon fiber and its composites. In order to solve this problem, extensive research has been carried out on the surface treatment of carbon fibers, such as plasma treatment, wet chemical oxidation, electrochemical oxidation and polymerization, vapor phase oxidation, surface modification using nanomaterials or chemical grafting, etc., which helps to improve the wettability, chemical bonding and mechanical interlocking between the fiber and the matrix, form a transition layer, promote the uniform transmission of stress, and alleviate the stress concentration, so as to have excellent performance and meet the comprehensive requirements of some scientific fields.

2.1 Plasma treatmentPlasma treatment has the advantages of simple operation, high efficiency and no pollution, and is a surface modification method that uses plasma with sufficient high energy to impact the surface of CF, resulting in surface chemical bond breakage and recombination, so as to achieve good adhesion between CF and resin. Zhang et al. found that plasma treatment time and polymerization conditions had a significant effect on the grafting rate, especially the plasma treatment time of 90s and the grafting concentration of 6 g/L. Fourier transform infrared spectroscopy showed that maleic anhydride disappeared and MAH was grafted on carbon fiber, and the absorbance was 1800cm-¹. The IFSS of carbon fiber/epoxy increases with the change of treatment method, especially the plasma grafting treatment. At the same time, it is indicated that the increase of interfacial adhesion is mainly due to the increase of surface activation groups. In addition, the carbon fiber performance of plasma grafting treatment has a reasonable improvement compared to plasma treatment. Yuan et al. modified the surface of carbon fiber by irradiation by microwave, which is a simple, fast and effective method. During the treatment, a highly reactive microplasma is produced by excitation of the carbon fiber, which introduces a large number of oxygen-containing groups on the surface of the carbon fiber. The detected nitrogen comes from the nitrogen heterocycles of the carbon fiber block, which is rich in the carbon fiber epidermal layer. The oxidation of the microplasma and the spalling of the monolayer GO greatly change the surface topography of the treated carbon fibers, resulting in an increase in surface roughness. The changes in the chemical and physical properties of the treated carbon fiber surface are beneficial for strengthening the interface bond between the carbon fiber and the epoxy matrix.

2.2 Oxidation treatmentThe main oxidation treatment is to peel, roughen and activate the CF surface through gas phase, liquid phase and electrochemical technology, which can significantly improve the active functional groups and roughness of the CF surface. However, the intrinsic strength of the fibers tends to be compromised by unmild oxidation conditions compared to sizing surface modifications. Jiang et al. modified the surface of carbon fiber (CF) by electrochemical oxidation combined with electrophoretic deposition. Graphene oxide (GO) is deposited on the surface of electrochemically oxidized CF, which improves the mechanical properties of carbon fiber reinforced epoxy composites. After electrochemical oxidation of CF by electrophoretic deposition, the surface roughness and wettability were improved, which proved to be a feasible method. The results showed that the GO coating was evenly distributed, and GO was firmly coated on the CF surface by covalent adhesion. In addition, the results of mechanical properties test show that the interlaminar shear strength and compressive strength of the composites are increased by 59.4% and 12.8%, respectively. The proposed continuous manufacturing process does not involve long processing times or complex chemical reactions, providing a potentially industry-compatible method for the fabrication of multi-scale GO/CF reinforcements.

2.3 Sizing coating modification

Sizing/coating modification is the formation of a coating with good compatibility between CF and resin by sizing or impregnation. This fiber surface coating can give the CF surface specific properties to different substrates, and has the advantages of high design flexibility, low cost, and good implementation.

He et al. developed a simple coating process in which carbon fibers are immersed in phenolic resin (NR) and an NR layer is applied to their surface. The effect of NR size on the interfacial properties of carbon fiber was measured by measuring ILSS, and the short beam shear test was used to measure it. Under optimal conditions, the bond strength is significantly improved. Liu obtained CFRP through vacuum forming process and introduced MWCNT into the surface of CF to form a multi-scale reinforcement material of CF-MWCNT. The acidified MWCNT adheres to the surface of CF with polar oxygen-containing functional groups, which can enhance the compatibility of CF with the resin matrix, thereby improving the interfacial chemical bonding. In addition, MWCNT attaches to the CF surface and constructs an active nanoscale rough surface, enhancing the interfacial mechanical bonding. The strength of the modified composites was higher than that of the unmodified composites by sizing treatment.

2.4 Chemical graftingChemical grafting modification is mainly to generate the required active functional groups on the CF surface, and continue to react with small molecules or large molecules, so as to graft more active functional groups to the CF surface to improve the interfacial strength. This method selectively grafts a variety of small molecules, polymers, and nanomaterials onto the CF surface. In order to improve the interfacial adhesion of carbon fiber/epoxy resin composites, Tang et al. grafted branched-chain polyethylenimine (PEI) onto CF treated with mixed acid, and optimized the process time. The results showed that low-molecular-weight PEI-modified CFs were better than high-molecular-weight PEI-modified CFs. The IFSS of PEI-modified CFs was up to 107.2±14.3 MPa under low functionalization, while the IFSS of unmodified CFs was 78.1±11.6 MPa. The branched structure and high density of the active amine groups on the PEI chain are responsible for the improved interfacial strength.

 3. Composite structure design

In addition to epoxy resin and carbon fiber surface modification, the structural design of composite materials also has a great impact on the mechanical properties. The interleaved method is another effective toughening technique that can achieve high-layer toughness while maintaining the original in-plane properties of composites. In addition, a sandwich structure can be used, such as adding a foam core to CFRP, which can improve the impact resistance of the material.

Zheng et al. improved the interfacial properties of composites through the bidirectional structural design of CF surface and resin to reduce the modulus difference and smooth the modulus transition. By increasing the resin modulus, the modulus difference between CF and resin is further reduced. In addition, the rigid-flex structure design of the CF surface creates a multi-level gradient interface that smooths and buffers the modulus from CF to resin. Compared to the multi-scale interface structure of the optimized interface, the above synergy allows for appropriate modulus matching, resulting in excellent interface performance. The experimental results show that the ILSS of the two-way structural design CF composites is 41.2% higher than that of the original CF composites, and the surface modification of CF only and resin only are increased by 17.7% and 8.0%, respectively. Therefore, the simultaneous construction of CF surface and resin at multiple scales can provide a new idea for the preparation of high-performance CF reinforced resin composites in the future.

Zhang et al. proposed a multi-scale cellulose fiber interlayer composed of chopped flax fibers (FFs) and cellulose nanofibers (CNFs) to enhance the interlaminar fracture toughness of carbon fiber/epoxy resin composites. The cellulose fiber interlayer was treated with water-based epoxy resin to improve the interfacial compatibility with the epoxy matrix. The results of the end notched bending show that the addition of cellulose fiber interlayer in the carbon fiber/epoxy composite significantly improves the interlaminar fracture toughness of mode II., which is due to the synergistic effect of FFs and CNFs. The three-dimensional network of minced FFs mitigates the agglomeration of CNFs due to its good compatibility, resulting in more fiber bridging and fiber pull-out during the stratification process. The presence of CNF further improved the interfacial properties of FFs and epoxy matrix, which was conducive to the fibrosis of flax fibers and hindered the growth of interlaminar cracks. Wang et al. proposed an effective interlaminar toughening strategy for CFRP laminates, i.e., the introduction of cross-layers made of CNC/polyetherimide (PEI) nanofiber mats. The study showed that the GIc and GHc of CNCs-reinforced PEI nanofiber interlayer were increased by 28% and 20%, respectively, compared to pure PEI interlayer. The toughening mechanism can be attributed to carbon fiber bridging, fiber necking, fiber and CNC polymer fracture, and CNC polymer needling effect on cracks. Fabric preforming, using three-dimensional weave, knitting, or braided preforms, can increase the toughness and resistance of the material to damage. Eun et al. used carbon fiber braid interwoven with polyamide fibers to enhance the mechanical properties and delamination resistance of carbon epoxy composite laminates. The carbon/epoxy composite laminate is interwoven with polyamide fibers to increase tensile strength by about 20%, residual strength by 31%, and critical energy release by about 120%. The improvement in mechanical properties and resistance to delamination is attributed to the chemical reaction cross-linking between the polyamide fibers and the epoxy resin.

5. Conclusion

The toughness of CFRP has seen remarkable advancements through resin modification, interfacial engineering, and structural design. However, balancing mechanical properties, sustainability, and functionality remains critical. Future breakthroughs will likely arise from multiscale synergies, green technologies, and intelligent material systems. As industries demand lighter, stronger, and more durable composites, cross-disciplinary collaboration between chemists, materials scientists, and engineers will be essential to unlock the full potential of CFRP in next-generation applications.

Significant progress has been made in the research on toughening and modification of carbon fiber/epoxy resin matrix composites, and the toughness of the materials has been effectively improved through epoxy resin modification, carbon fiber surface modification and structural design. However, in the face of the increasing demand for high performance and multi-functionality, the research and application of composite materials still face many challenges, and it is necessary to further explore the mechanism of action of new nanomaterials, develop more efficient and environmentally friendly interface modification technologies, and innovate structural design concepts to achieve reliable performance of materials under extreme conditions.

Therefore, continuous innovation and multidisciplinary collaboration will be key to advancing the field. Through interdisciplinary research in the fields of materials science, chemical engineering, and mechanical design, the performance of carbon fiber/epoxy matrix composites can be comprehensively improved to meet the increasingly stringent application requirements in aerospace, automobile manufacturing, construction engineering and other fields. At the same time, with the emphasis on environmental protection and sustainable development, the research on greener and renewable toughening modification methods will also become an important direction in the future. Together, these efforts will drive the continued progress and widespread adoption of carbon fiber/epoxy matrix composites.