Fracture Toughness Of Composites Research Articles

Effect of dual dispersion of carbon fiber and silica nanoparticles on recovery performance of shape memory epoxy

Abstract Shape memory polymers (SMP) are utilized in diverse fields, including deployable structures and components, owing to their advantageous properties like low density, cost-effectiveness, and ease of processing. The current study investigates the effect of dual dispersion of carbon fibers (CF) and silica nanoparticles (SN) on the recovery performance of shape memory epoxy composites. CF (0.25 wt.%) reinforced epoxy composite, SN (0.25 wt.%) reinforced epoxy composite, and dual (CF and SN 0.25 wt.% each) dispersed epoxy composite were developed using magnetic stirring and ultrasonic mixing to study the mechanical properties and shape memory behaviour. Flexural strength, tensile strength and fracture toughness of pristine epoxy was found to be 134.38 MPa, 52.15 MPa and 1.91 MPa∙m1/2, respectively. The addition of CF resulted in a flexural strength of 135.70 MPa and a tensile strength of 53.01 MPa, while the incorporation of SN led to a flexural and tensile strength of 138.40 MPa and 53.69 MPa, respectively. The fracture toughness of composites after adding CF and SN was found to be 2.22 MPa∙m1/2 and 2.39 MPa∙m1/2, respectively. With dual dispersion, the flexural strength of 139.82 MPa, tensile strength of 54.64 MPa, and fracture toughness of 2.75 MPa∙m1/2 were achieved. Dual dispersion has shown improved mechanical properties compared to single dispersion. The introduction of CF slightly decreased the shape fixity ratio (Rf) and shape recovery ratio (Rr) of the pristine epoxy from 98.67% and 96.62% to 96.67% and 95.15%, respectively. Similarly, the addition of SN further reduced these ratios to 98.00% and 91.83%, respectively. With a dual dispersion approach Rf and Rr were observed to be about 97.33% and 93.83%, respectively. The addition of fillers led to a reduction in Rf and Rr due to inhibition of polymeric chains, resulting in partial shape recovery. However, recovery time improved from 28 s to 23 s and 26 s with addition of CF and SN, respectively, in epoxy. With dual dispersion, a speedy recovery was achieved with a recovery time of 21 s. The findings of this study demonstrate the potential of dual dispersed fillers to improve the mechanical and shape memory properties of epoxy, which could find applications in the smart materials and structural engineering.

Fracture toughness evolution and failure mechanisms of two-dimensional SiCf/SiC composites at temperatures up to 1500 °C in air

Silicon carbide fiber reinforced silicon carbide composites (SiCf/SiC) are of the few most promising materials for high-temperature structural applications. In this study, two-dimensional (2D) plain-woven SiCf/SiC composites were prepared by chemical vapor infiltration process and subjected to single-sided notched beam three-point bending tests from room temperature (RT) to 1500 °C in air. The temperature-dependent bending load–deflection curves and fracture toughness were obtained. The results show that the SiCf/SiC composites exhibit linear deformation characteristics initially, followed by nonlinear deformation behavior which become more pronounced with increasing temperature. The fracture toughness decreases in the range of RT to 1000 °C due to the evolution of components properties, and increases at 1200 °C due to the interface property degradation and fiber pull-out. Above 1200 °C, it decreases with increasing temperature owing to the serious high-temperature oxidation. Further, the failure mechanisms of the 2D plain-woven SiCf/SiC composites at different temperatures was analyzed through macro and micro analysis. The evolution of components properties affected by high temperature and oxidation as well as fiber pull-out play a leading role in fracture toughness of composites. The findings of this study provide important support for the mechanical behavior and failure mechanisms of SiCf/SiC composites at ultra-high temperatures in air.

Effect of curing process on shear and interlaminar fracture toughness of vinylester urethane-glass fibre composites

The influence of the curing process on the interlaminar shear strength and mode II toughness of Vinylester-Urethane resin composites with high density glass fibre plain fabric is shown in this work. There is a shorter curing treatment that achieves similar mechanical properties compared to the treatment proposed by the resin manufacturer. This is of industrial interest as shortening time leads to savings in production costs.

Energy transfer and release during the fracture of UD fiber-reinforced thermoplastic composites

This study delves into the complex dynamics of energy transfer and release during the fracture of unidirectional (UD) fiber-reinforced thermoplastic composites. Conducted through meticulous experimental observations and rigorous energy analysis, the research presents groundbreaking conclusions on the fracture toughness and energy conversion efficiency of UD carbon fiber composites under various loading conditions. A prominent focus is on how these mechanical properties are intricately linked to the sample’s fiber orientation angles and the external conditions applied during testing.The work employed tapered double cantilever beam (TDCB) as the far-field boundary to investigate the energy changes, transfer, and conversion processes during the crack propagation of unidirectional fiber reinforced thermoplastics (UDFRTPs) structures. It was found that throughout the entire propagation process, blunt extension occurs first followed by inertial extension. This is because in the initial stage of crack propagation, the stored elastic energy in the structure is relatively small, making the crack tip prone to blunting. This continuous blunting impedes the release of internal strain energy in the structure, with blunt extension accounting for a very small proportion of the entire fracture process. When the internal strain energy in the structure continues to increase to a certain extent, the blunting of the crack tip cannot prevent the release of a large amount of elastic energy inside the structure. At the same time, the excess released strain energy converts into kinetic energy and continually impacts the blunted region at the crack tip. At this point, the propagation transitions into the inertial extension stage, which occupies a significant portion of the entire fracture process.

Enhancement fracture behavior of sustainable cementitious composites using synergy between fly ash (FA) and nanosilica (NS) in the assessment based on digital image processing procedure

The present study has investigated the strength properties and fracture toughness of concrete composites reinforced 5 % nanosilica (NS) by adding different contents of fly ash (FA), i.e.: 0 %, 15 % and 25 %. The evaluated fracture toughness, under three-point flexural loads, were critical stress intensity factor (KIcS) and critical crack tip opening displacement (CTODc). Digital image processing procedure was used in this studies. It was stated that both the 5 % addition of NS and the total share of the nanomodifier with FA grains in the composition of the concrete mix significantly improve the strength properties of concretes, as well as their fracture toughness under first model of cracking in linear and non-linear terms. Moreover, it was observed that in concrete containing only NS the fracture process was clearly delayed and relatively short, whereas crack patterns in this composite were almost perfectly straight with significant crack width. On the other hand, in concretes icorporating NS + FA crack patterns were strongly curved (frequently with branching) with few microcracks in the vicinity of the main cracks. Concretes including FA and NS can be used in the execution of specific types of reinforced concrete structures subjected to fatigue or dynamic loads, e.g. bridge structures or industrial buildings.

Investigation of fracture behavior and mechanical properties of epoxy composites supported with MWCNTs microscopically

Adding of a multi-walled carbon nanotubes (MWCNTs) to epoxy resin has shown promising results in improving fracture toughness in bulk epoxy and carbon fiber-reinforced epoxy composites (CFRP). using a hand layup proceeding followed by the so called vacuum bagging process method, carbon fiber-reinforced polymer multi-wall carbon nanotubes (MWCNTs) was added to an epoxy resin with a weight percentage mixing of 1% wt., 1.25% wt., and 1.5 % wt. MWCNTs. Furthermore, the specimen underwent analysis via Fourier-Transform Infrared (FTIR) spectroscopy, and X-ray Diffraction (XRD) spectroscopy, the composites were subjected to a microscopic examination using a Scanning Electron Microscope (SEM). FTIR and XRD verified the folding and unfolding of the polymer, in addition, the mechanical properties including tensile strength, bending stress, and impact behavior were investigated as well as the hardness test. The obtained results showed a significant improvement of about (40 %) in tensile strength, (53 %) in bending stress at 1 % wt. MWCNTs, and (70 %) percentage increment in the strength of Impact at 1.25 % wt. MWCNTs. And the gained hardness was about 40.5 HV which were compared with a reference substance named Carbon Fiber (CF) without any addition of nano materials. Carbon nanotubes have demonstrated their potential to enhance the mechanical properties of fiber-reinforced polymers, so this investigative study employs comprehensive characterization techniques, and demonstrates significant improvements in mechanical properties for the modified polymeric composite materials supported with nano materials.

Formation of heterogeneous interfaces in the TiAl/Ti2AlNb layered composite and its effect on the fracture toughness

TiAl/Ti2AlNb intermetallic-intermetallic laminated (IIL) composites featuring brittle/ductile heterogeneous interfaces were fabricated through vacuum hot-pack rolling. The microstructures and the phase transformation behaviors of the interfaces of the IIL composites before and after annealing at 900 °C/6 h were investigated. The heterogeneous interfaces are composed of four distinct regions, individually I (βo+γ+α2), II (βo/B2+ω) (brittle part), III (O lath), and IV (equiaxed O) (ductile part) regions from TiAl to Ti2AlNb side. Notably, after annealing, an equiaxed O band approximately 50 μm wide was observed in region IV of the interface. In addition, a significant microhardness variation was observed between regions II and IV of the interface, where region II exhibited higher hardness compared to the TiAl alloy, and region IV displayed lower hardness than the Ti2AlNb alloy. The enhanced fracture toughness of the IIL composites, three times that of the TiAl base alloy, is attributed to the formation of the brittle/ductile heterogeneous interfaces and the layered design incorporating the Ti2AlNb alloy. The corresponding toughening mechanism was further discussed. The brittle II region plays a role in increasing crack branching, while the ductile IV region inhibits the propagation of microcracks and prevents the formation of main cracks. This work highlights the crucial role of the brittle/ductile heterogeneous interface in the toughening of laminated composites. Furthermore, the discovery of the O band provides novel insights into the design of TiAl/Ti2AlNb heterostructures.

The effect of resin properties on toughness translation in interleaved composites

Interleaving is a well-recognized method for enhancing the interlaminar fracture toughness of composite materials. However, theoretical toughness is often not realized since cracks tend to propagate through regions of lower toughness. While most studies have focused on the effect of interleaf properties, e.g., thickness and interleaf resin properties, on composite interlaminar fracture toughness, the effect of matrix resin properties on interleaved composite toughness has been overlooked. Recently, we hypothesized that there is a relationship between toughness translation and the ratio of matrix to interleaf resin toughness. In this work, we use additive manufacturing to test this hypothesis with a range of resins in interleaved composite. Toughness is quantified via mode I delamination resistance. Our results confirm our hypothesis that the ratio of matrix to interleaf resin fracture toughness, i.e., the ratio of [Formula: see text], is directly correlated to the degree of toughness translation. More specifically, a ratio of approximately 0.5 is required for effective interleaving; below 0.5, the toughness translation is significantly below the theoretical value. This approach has important implications for the design and fabrication of tough composites via choice of resins.

On the high fracture toughness of wood and polymer-filled wood composites – Crack deflection analysis for materials design

Cracks oriented in the toughest direction across the grain of wood (0°) tend to deflect at 90° to the precrack rather than extending in 0° direction. Fracture toughness data across the grain are therefore difficult to interpret. Crack growth mechanisms and effects from replacing wood pore space with a polymer are investigated. Crack growth is analyzed in four-point bending fracture mechanics specimens of birch and two different polymer-filled birch composites using strain-field measurements and finite element analysis (FEA). Calibrated cohesive zone models in both precrack and 90°-directions describe fracture process zone properties in orthotropic FEA-models. Conditions for 0° crack penetration versus 90° crack deflection are analyzed based on cohesive zone properties. Stable, subcritical crack deflection takes place at low load, reduces crack tip stress concentration, and contributes to high structural toughness, provided the 90° toughness is not too low. Polymer-filled neat birch composites have the best structural toughness properties in the present investigation, since 90° toughness is not compromised by any chemical treatment.

Fracture toughness and fiber bridging mechanism for mode-I interlaminar failure of spread-tow woven composites

Given the current lack of research data on the delamination behavior of spread-tow woven composites, this study aims to systematically characterize the mode-I interlaminar fracture behavior of plain weave spread-tow fabrics (STFs) composites. DCB tests were conducted to investigate the influence of different ply thicknesses, unit cell sizes, and interface angles on delamination behavior and fiber bridging. The experimental results revealed a stick–slip crack propagation behavior in mode-I delamination of studied material, and a detailed analysis was performed on the influence mechanism of unit cell size on this behavior. Fiber bridging was found to be the primary mechanism responsible for the increased interlaminar fracture toughness in the plain weave STFs composites. Fractography analysis indicated that regions rich in fibers and resin in thicker-ply laminates promote fiber bridging, while an interface angle inconsistent with the direction of crack propagation inhibits fiber bridging. The concept of average steady-state fracture toughness (average Gs) was introduced as a means to assess propagation fracture toughness and two methods were proposed to obtain bridging tractions for characterizing the fiber bridging phenomenon. The bridging tractions and average Gs were used as key parameters to establish a trilinear cohesive zone model (CZM) for simulating mode-I delamination. The numerical results aligned well with the experimental results, demonstrating the applicability of the parameter determination strategy based on the average Gs and bridging tractions for the selection of parameters to use in the CZM.

Synergistic toughening modification and finite element analysis of carbon fiber/epoxy resin‐reinforced composites

AbstractIn this work, the poor fracture toughness of carbon fiber‐reinforced composites (CFRPs) was improved by the introduction of a graphene oxide/nanosilica (GOS) hybrid, and short carbon fibers (SCFs) were investigated through experimental and modeling methods. The effects of the SCF content, number of SCF layers, and introduction position on the mode I fracture toughness (GIC) and mode II fracture toughness (GIIC) of the composites were considered for epoxy resin (EP) modified by GOS. The results showed that GOS and SCF exhibited a synergistic toughening effect on CFRP. The GIC and GIIC of CFRP laminate with GOS content of 0.2 wt% and SCF content of 0.4 wt% reached 0.506 and 2.15 kJ/m2, increased by 72.2% and 53.6% compared to the unmodified composite, respectively. The number of layers and the lamination mode of GC10S5‐B specimens exhibited the optimal improvement of interlaminar fracture toughness. Similarly compared with those of the original. The GIC and GIIC of the CFRP laminates reached 0.662 and 0.506 kJ/m2 (enhanced by 125.9% and 95%, respectively). In addition, the stress propagation path and distribution, and progressive damage of the CFRP composites were obtained to further reveal the toughness mechanism.Highlights Synergistic toughening of resin modification and short carbon fiber on modes I and II fracture toughness of composites were considered. Content of short carbon fiber and lay‐up methods on toughness performance were investigated thoroughly. Finite element models were established to reveal the stress progress and distribution and toughness mechanism.

Investigation of interlayer toughening of carbon fiber composites using non-woven polyamide veils under different curing pressures

Carbon fiber-reinforced composites have become increasingly favored in the aerospace and automotive sectors for their remarkable performance attributes. Nonetheless, their broader adoption is hindered by the concern of delamination. To address this limitation, our study delved into the influence of incorporating a thermoplastic toughening agent on the interlaminar fracture toughness (ILFT) of woven carbon fiber composites. Our investigation focused on the impact of diverse curing pressures on these composites, analyzing configurations both with and without an integrated non-woven polyamide (PA) veil. The PA veil was meticulously positioned within the central layer of a composite, combining benzoxazine and carbon fiber constituents. Our primary objective entailed optimizing curing conditions to enhance ILFT across both Mode-I and Mode-II fracture modes. Our findings unveiled that elevating curing pressure had a limited effect on ILFT in non-interleaved composites while interleaved samples exhibited substantial ILFT reductions under heightened curing pressure. Raising pressure from 1 atm to 3.5 atm caused approximately a 27% drop in the Mode-I strain energy release rate (GIC) value, and this reduction deepened to 42% at 7 atm. This highlighted the inverse relationship between increased curing pressure and GIC values in interleaved specimens, while non-interleaved counterparts experienced less pronounced changes. A parallel trend manifested in Mode-II ILFT, where escalated curing pressure correlated with diminished Mode-II strain energy release rate (GIIC) values. Interleaved samples suffered a notably more significant decline, attributed to resin content reduction caused by heightened pressure. This, in turn, compromised the bond between the PA veil and the matrix, facilitating the propagation of cracks within the composite. This ultimately culminated in significantly reduced GIC and GIIC values. Our study contributes valuable insights into optimizing the interlaminar fracture toughness of carbon fiber composites, shedding light on the complex interplay of curing conditions and material configurations.

Effects of carbon/glass nonwoven interleaving veils and their areal density on opening and shearing mode interlaminar fracture toughness of glass epoxy composites

The study explores the impact of Carbon and Glass nonwoven interleaving veils with varying areal density on delamination resistance in unidirectional (UD) Glass epoxy composites under Opening (Mode-I) and Shearing (Mode-II) mode loadings. Commercially available non-woven Carbon and Glass interleaves with areal densities of 15, 20, 25, and 30 g/m2 were used to manufacture the interleaved Glass epoxy laminates. Double Cantilever Beam (DCB) and End Notch Flexural (ENF) specimens were used to determine the mode-I and mode-II fracture energies. The results reveal that, during mode-I initiation, interleaved laminates exhibit a lower interlaminar fracture toughness (IFT) except for the Carbon fiber interleaved laminates of areal density 30 g/m2. However, during propagation, all veils interleaved laminates presented significant improvement in IFT ranging from 5 to 25 % accompanied by substantial fiber bridging. In case of mode-II test, the laminates with Carbon and Glass veils exhibit enhanced IFT (60–182 %) with increasing areal density compared with the non-interleaved Glass laminates. Optical and scanning electron micrographs (SEM) provide evidence of fracture mechanisms involved in the interleaved and non-interleaved composite laminates.

An experimental investigation of the mechanical properties and failure mode of 3D stitched composites

Mechanical behavior and failure modes of three-dimensional (3D) stitched composites were experimentally investigated. In addition, a comparative analysis between these materials and equivalent laminates (2D) was accomplished. The 3D composite plates were manufactured using sheets of glass fiber manually sewn with aramid tows and molded with epoxy resin by vacuum-assisted resin transfer molding. Three-points bending, Charpy impact, double cantilever beam (DCB), and short-beam shear (SBS) mechanical tests were carried out on both types of materials. The DCB test results revealed that the action of reinforcement tows inhibited the propagation of the delamination cracks, which led to an increase in the fracture toughness of the 3D composites. However, the damage caused by the stitching process, such as fiber breakage and misalignment as well as crimping, and resin-rich regions, was responsible for reducing the flexural and shear properties of these materials. In addition, it was revealed that the stitching did not influence the impact toughness, although it prevented delamination from quick propagation, avoiding a catastrophic failure, which enhanced the damage tolerance of these materials, mainly for aeronautical applications.

Milled graphitic nanoparticle toughened epoxy composites via increased resistance to in-plane crack propagation

Fascinating features of 2D-based carbon materials like graphene have drawn increasing attention to fulfill the desire to enhance the fracture toughness of epoxy composites. However, challenges remain to improve their dispersibility in polymers and increase interaction ability. Thus, work is needed to synthesize alternative cost-effective 2D carbon nanofillers capable of delivering consistent performance as a reinforcer to monitor the fracture toughness of the epoxy composites. The present study demonstrates transforming graphite to ball-milled graphite (BMG) via an effective high-energy wet ball milling process. Herein a noteworthy size reduction is achieved for the BMG ranging from ∼217 to 227 nm. Microscopic investigation spotted an exfoliated 3D networked graphite nanosheet with nanopores. These BMGs were functionalized to attach amine-based silane moieties and were incorporated into the epoxy network. Consequently, even at higher loading levels, they showed their astonishing capability to enhance the crack far field resistance of nanocomposite resulting in significantly improved fracture toughness and energy to ∼2.31 MPa m1/2 and ∼11.30 kJ/m2, respectively. Improvement is ascribed to the better dispersing ability of BMG, which provides a consistent strong interfacial interaction with the epoxy network to modulate material resistance to fracture. Such environmentally friendly nanofillers must be industrially acceptable for synthesizing durable epoxy nanocomposite systems and can be utilized to prepare structural composites.

Investigating the impact of extreme environments on the interlaminar performance of nanoparticle-reinforced carbon fiber composites

This study investigates the influence of extreme environmental conditions on the fracture toughness of halloysite nanotube (HNT)-reinforced carbon fiber-reinforced polymer (CFRP) composites. The focus is on the impact of exposure to high humidity and its effects on the mechanical properties of the composites. The study reveals that exposure to high humidity enhances the fracture toughness of HNT-modified CFRP composites, attributed to the entrapped moisture between HNTs and the polymer matrix. This phenomenon enhances crack bridging and contributes to improved mechanical properties. Furthermore, the HNT-modified composites exhibit superior environmental degradation resistance compared to unmodified composites, demonstrating the potential of HNTs as reinforcement for advanced composite materials. The investigation underscores the significance of considering environmental factors in nanoparticle-reinforced composite design and applications, paving the way for the development of durable, high-performance materials capable of withstanding extreme conditions. The findings emphasize the need for continued research to enhance the durability and reliability of such composites, thereby offering sustainable solutions across a range of applications. This study contributes valuable insights towards the design and optimization of fracture-resistant composite materials for demanding environments.

Mode I fracture toughness with fiber bridging of unidirectional composite laminates under cryogenic temperature

Carbon fiber reinforced polymer (CFRP) composites have widely been used in the aerospace field owing to their excellent mechanical properties. However, composite structures often fail under complex space environmental conditions. In particular, the fiber bridging and cryogenic temperature may greatly change the fracture toughness of CFRP composites. Herein, the effects of cryogenic temperature and fiber bridging on the fracture toughness of unidirectional composite laminates were experimentally examined by double cantilever beam (DCB) testing at different temperatures (room temperature, −50 °C, −70 °C, −100 °C, −150 °C, and −180 °C). Different calculation methods of fracture toughness were used and the results were compared. A method without measuring the delamination length at low temperatures was used and the results were consistent with other methods. The average difference in fracture toughness values was less than 5 %. The fiber-bridging microstructures of composites under cryogenic temperatures were examined by confocal microscopy along with the geometric morphology and parameters of surface roughness. The results suggested changes in the matrix failure mechanism at −50 °C, resulting in maximum fracture toughness, which is 26.45 % higher than that at room temperature. A semi-analytic approach was then proposed to express the bridge stress, and a bilinear cohesive zone model was established to simulate the delamination of composite laminates at low temperatures. Overall, the numerical data agreed well with the experimental results (peak force maximum error of 17 %), suggesting the usefulness of the proposed method for the prediction of interlamination properties and structural damage design of composite structures at cryogenic temperature.

Multi-scale synergistic toughening of glass fiber/epoxy laminates with carbon nanotube-modified carbon fiber felt

Hierarchical toughening is commonly found in natural materials such as teeth, bone and seashells, which have evolved to withstand mechanical stresses. The incorporation of this mechanism into the design of synthetic materials, such as composites, has drawn much attention in recent decades. In this work, a carbon fiber felt (CFF) made of short carbon fibers was spray-coated with carbon nanotubes (CNT) to create a hierarchical structure that can be directly interleaved into glass fiber reinforced polymer (GFRP) composites for interlaminar toughening purpose. The results showed that the highest enhancement of GIC,ini and GIC,prop values reach as much as 211 % and 174 %, respectively, which far outweighs the state of the art. The fracture surfaces as well as crack propagation behaviors were comparatively investigated to get deep insight into the toughening mechanisms. It was found that multiscale fiber bridgings and interlaminar crossings are the key to achieving high interlaminar fracture toughness of laminate composites.

Tribocorrosion of TiC-based composites incorporating Ni and Co binders in saline solutions

Metallic binders impart necessary toughness to ceramic-metal composites, yet are vulnerable to corrosion and wear. Thus far, the tribocorrosion mechanism remains little understood, obstructing the design of durable composites for ocean drilling applications. Against this backdrop, we selected the TiC-based composites encompassing the Ni and Co binders having different standard electrode potentials as model systems, and studied their tribocorrosion behaviors with the aid of microscopic characterizations and first-principles calculations. Results showed that the TiC-Ni system maintained lower corrosion current densities at the pure corrosion condition, due to the reduced tendency of galvanic corrosion. Such system also realized lower coefficient of friction (COF) and wear losses at the pure wear condition, benefiting from the reduced adhesion at the sliding interfaces as well as the improved composite fracture toughness. Under corrosion-wear interactions, however, the TiC-Co system revealed alleviated material losses, as the rapid build-up of oxide tribolayers enhanced the surface hardness and facilitated the transfer layer formation. Thus, contrary to the intuition that corrosion-resistant binders should be beneficial to the tribocorrosion resistance, the current work highlighted the binder's ability to generate surface layers that helped to resist corrosion-accelerated wear, a point that needs to be emphasized in future development of robust composite materials.

Effect of CNT filler and temperature on fracture toughness of epoxy composites reinforced with carbon fabric

AbstractIn present research the fracture behavior of carbon fabric‐epoxy composites (CE composites) was evaluated with the addition of 0.1, 0.2, 0.5, and 0.75 weight percentages of carbon nano tubes (CNTs) at different temperatures. The CE composites with different wt.% of CNT were fabricated using land layup method and cured by hot pressing. The fracture toughness of fabricated composites was evaluated in mode–I condition at different temperature. From the results it was shown that the highest fracture toughness was observed at 0.75 wt.% of reinforcement of CNT functional fillers. The fracture toughness of 0.75 wt.% CNT filled CE composites was increased by 19.73% compared to unfilled CE composites. The fracture toughness of CNT filled CE composites diminishes with increase in temperature and the composite filled with 0.75 wt.% CNT exhibits better fracture toughness than the unfilled CE composite at all the temperatures. The fracture toughness was improved by 57.76% and 71.65% at 40 and 60°C, respectively, at 0.75 wt.% reinforcement of CNT fillers. The fractured surfaces of composites were analyzed using Scanning Electron Microscope (SEM) to study the filler contribution to enhance the fracture toughness and failure mechanism of composites.