Number Of Freeze-thaw Cycles Research Articles

Technology of making asphalt concrete using sand slag

In the Central Black Earth Region, there are settlements that do not have hard-surfaced access roads, and existing access roads require major repairs. In order to reduce the cost of construction, it is proposed to use asphalt concrete mixtures from slag materials for the construction of road pavements. Slag materials have hydraulic binding properties; the processes of structure formation in them take a long time. The study of the properties of asphalt concrete was carried out depending on the time from the moment of manufacture, after prolonged water saturation and the number of freeze-thaw cycles. The obtained results indicate an increased durability of asphalt concrete road pavements made of slag materials.

Effects of freeze-thaw treatment and pullulanase debranching on the structural properties and digestibility of lotus seed starch-glycerin monostearin complexes

The effects of multiple cycles of freeze-thaw treatment, combined with pullulanase debranching, on the structural properties and digestibility of lotus seed starch-glycerin monostearin complexes were investigated. The formation and melting of ice crystals during freeze-thaw treatment disrupted the crystalline structure of the starch granules, creating pores which facilitated access of pullulanase to the interior of the granules. Pullulanase debranching increased the free amylose content of the starch, which promoted the formation of starch-lipid complexes, which, in turn, increased the proportion of resistant starch and the overall resistance of the starch to digestive enzyme action. These effects increased with the number of freeze-thaw cycles, because more cycles increased both the disruption of the granule structure and the extent of pullulanase debranching. These findings provide a basis for the preparation of functional foods with low glycemic indices, which have strong potential for management of type II diabetes.

Evaluation of the bearing capacity of poor subgrade soils stabilized with waste marble powder according to curing time and freeze-thaw cycles

In this study, pavement subgrade soils were stabilized with two difference types of waste marble powder, and California bearing ratio (CBR) tests were conducted to evaluate the improvement in their bearing capacity. To this end, highly plastic silt (MH) and highly plastic clay (CH) layers were used as the subgrade soil material. A number of unsoaked CBR tests were conducted on the test samples by adding a varying percentage of calcitic marble powder (CMP) and dolomitic marble powder (DMP) using different freeze-thaw cycles (0, 1, 3, 5, 7, and 11 cycles) and curing times (0, 7, 30, and 60 days) in the laboratory. The waste marble powder ratios were taken as 5, 10, 20, 30, and 50% by the dry weight of each soil specimen. SEM and energy dispersive X-ray (EDAX) analyses were also performed on the specimens to determine the efficiency of the marble powders. According to the comparison based on the CBR values, the inclusion of an appropriate amount and type of waste marble powder positively affected the bearing capacity of the subgrade soil samples regardless of curing time and number of freeze-thaw cycles. Moreover, both curing time and freezing-thawing cycles influenced the CBR values depending on the waste marble powder type and content and subgrade soil type.

Stress–Strain Assessments for Buried Oil Pipelines Under Freeze-Thaw Cyclic Conditions

Abstract In this study, outdoor freeze-thaw cyclic tests on the Q345 steel pipeline portion were conducted to analyze the buried oil pipeline stress evolution in a seasonally frozen soil area, namely, the Mohe–Daqing portion of China–Russia crude oil pipeline. The results obtained show that under the freeze-thaw cycle, the variation trend of soil temperature around the pipeline exhibited a hysteresis pattern, which was similar to that of atmospheric temperatures. The soil frost heaving force was shown to drop with depth, and its value at the pipe top was higher than that at the pipe bottom. With the number of freeze-thaw cycles, the frost heaving force of the soil first increased and finally stabilized, while the principal stress of the pipeline increased gradually, and its extreme value tended to be stable after 7–8 cycles, which was consistent with the “ratchet effect” theory. The above findings made it possible to elaborate on a more efficient freeze-thaw cyclic test setup for clarifying the mechanism of frozen soil/pipeline interactions.

Effect of Freeze-Thaw on Compressive Strength of Clayey Soils Reinforced with Wool

ABSTRACT Reinforcing clayey soil using synthetic and natural fibers has been widely used as soil improvement methods in recent years. The usage of wool, which is inside the natural fibers, as a reinforcing material is seen as an economic, sustainable, and environmentally friendly solution. The compressive strength parameters of clayey soils (CS) equipped with wool were determined by a series of free pressure strength tests before and after freeze-thaw (F-T). The F-T cycle was repeated 12 times in cycles 1, 7, and 28 days. The highest strength increase was attained after 28 days of curing. The compressive strength increase of CS samples prepared with four different wool additives (0.5%, 1%, 1.5%, and 2% dry weight) occurred between 16.9–68.7% and 13.3–62.7% before and after F-T, respectively. The highest compressive strength increase before and after F-T occurred in CS+1.5% wool mixture. In addition, the wool ratio and the number of freeze-thaw cycles were determined to be important parameters in the increase in compressive strength. In summary, it is concluded that wool-supported CS can be used in the basic design of engineering structures and in shallow depths especially in regions with cold climates.

Freeze-thaw and wetting-drying effects on the hydromechanical behavior of a stabilized expansive soil

This study evaluates the effects of post-compaction wetting–drying (WD) process, freeze–thaw (FT) cycles and cement content (CC) on the microstructure, volumetric strain (εv), soil–water characteristic curve (SWCC), resilient modulus (MR), unconfined compressive strength (qu), and reloading modulus (E1%) and axial stress (Su1%) at 1% strain level of a cement-stabilized expansive soil. The specimens compacted with different CC (i.e. 0%, 2%, 4% and 6%) were subjected to different number of FT cycles (i.e. NFT = 0, 1, 3 and 10). They were then dried or wetted to different moisture contents before the determination of the (i) SWCC using filter paper method, (ii) MR from cyclic triaxial tests, and (iii) qu, E1%, and Su1% from unconfined compression tests. The microstructural changes in the test specimens were determined using mercury intrusion porosimetry and scanning electron microscope tests. Experimental results reveal that cement stabilization and cracks induced during FT cycles cause a significant reduction in the specimen’s water retention capacity and the scale of volumetric strain upon moisture content fluctuation. The MR, qu, E1% and Su1% typically decrease with NFT but increase with CC. However, their variation with moisture content changes is less significant after stabilization or FT cycles. Performance of several empirical models for predicting the MR, qu, E1% or Su1% was examined. Similar trends in behavior were found for MR-qu, MR-E1% and MR-Su1% relationships for the specimens tested with different CC, NFT and water content. A simple hyperbolic model proposed in this study for predicting these relationships is validated. The studies presented in this paper are helpful for the design and analysis of stabilized expansive soils used as pavement subgrade considering the influence of complex environmental factors.

Shear Strength and Microstructure of Intact Loess Subjected to Freeze‐Thaw Cycling

In the Loess Plateau, seasonal freeze and thaw cause great damage to the mechanical behavior and microstructure of soil, which leads to frequent geological disasters during winter and spring. To investigate the influence of freeze‐thaw (FT) cycling (FTC) on the shear strength and microstructure of intact loess, triaxial shear, nuclear magnetic resonance, and scanning electron microscope tests were carried out on soil samples after target FT cycles. The results indicate that the FTC has limited changes to the soil stress‐strain curve, but has a significant attenuation effect on the peak deviatoric stress. The peak deviatoric stress was attenuated by FTC but changed insignificantly after ten cycles. The cohesive force decays exponentially with the number of FT cycles, while the internal friction angle increases slightly. Moreover, under FTC, the T2 hydrogen spectra of soil samples showed a multimodal distribution, with the main peak appearing to have two obvious upward shifts that occurred at 6 and 10 FT cycles. Indeed, a depolarization phenomenon related to the directional frequency of soil particles was observed, and the mass fractal dimension of the pore network increased slightly. In an FT environment, the shear strength declines due to accumulated internal microstructural damage. These findings contribute to a better understanding of the response of loess to FTC and provide novel ideas for the prevention of frost damage in loess areas.

Triaxial Creep Behavior of Red Sandstone in Freeze-Thaw Environments

To investigate the time-dependent mechanical properties of rock masses in cold regions under the effects of freeze-thaw cycling and long-term loading, triaxial multilevel loading and unloading creep tests were performed on saturated red sandstone samples subjected to different numbers of freeze-thaw cycles. The effects of freeze-thaw cycles and confining pressure on the creep properties, long-term strength, and creep failure mode of the rock were analyzed. The effect of freeze-thaw cycles on the microstructure of the rock was analyzed using scanning electron microscopy. The results showed that as the number of freeze-thaw cycles increased, the rock particle boundaries became more distinct, and more pores formed. The effect of freeze-thaw cycles on the creep deformation of red sandstone was related to the loading stress level. At low stress levels, the rock viscoelastic strain increased gradually and almost linearly with an increasing number of freeze-thaw cycles; in contrast, at high stress levels, the rock viscoelastic strain increased nonlinearly. The viscoplastic strain increased almost linearly with increasing freeze-thaw cycles. The fourth loading stress level (70% σ c ) corresponded to the transition of the creep deformation of the red sandstone. When the confining pressure was low, a higher stress level caused the confining pressure to have a more significant effect on the creep strain. However, as the confining pressure continued to increase, the effect of the confining pressure on the creep strain eventually disappeared. The long-term strength of the red sandstone decreased approximately linearly with an increase in the number of freeze-thaw cycles. When the number of freeze-thaw cycles and the confining pressure were high, the rock samples formed a transverse shear plane and were more fragmented than those without a transverse shear plane. These results provide a reference for construction in rock mass engineering and long-term stability analysis in cold regions.

Effects of freeze-thaw cycles on the characteristics of the expansive soils treated by nanosilica and Electric Arc Furnace (EAF) slag

The problematic expansive soils are spread in many countries and require significant improvement. The impacts of nanosilica and the Electric Arc Furnace (EAF) slag on the improvement of the swelling potential, volume changes, and Unconfined Compressive Strength (UCS) of the expansive clay samples were experimentally investigated in this study. In addition, the durability of the stabilizers against adverse effects of consecutive freeze-thaw cycles was also assessed using macro and micro tests. The results showed that the expansibility of the soil samples improved by 20% of the EAF slag and 0.5% of nanosilica decreased by 77.5% after one day of curing. To evaluate the durability of the samples, the number of freeze-thaw cycles was repeatedly increased until the dynamic equilibrium was reached. Then, the volume and water content changes and also the strength reduction rate of the treated and untreated samples were measured at the end of each cycle. The results revealed that the dynamic equilibrium for both untreated and treated samples was recorded during the 2nd to 4th cycles. The highest strength reduction rate occurred after the 1st and 2nd cycle and it was respectively 29% and 36% for the untreated and only 14% and 18% for the treated samples by the optimal amount of the EAF slag and nanosilica after 7 days of curing. However, the strength reduction rate decreased to 5.4% and 6.4% after 28 days of curing, thus curing time brought the significant improvement and promising results for the treated samples against the freeze-thaw cycles. In addition, the maximum volumetric strain was measured as 6% for the untreated expansive clay, occurring after the 4th freezing cycle. However, this value decreased significantly to 2.75%, occurring after the 3rd freezing period, for the sample improved by nanosilica and the EAF slag simultaneously. Thus, the results confirmed the strong potential use of the mixture of the EAF slag and nanosilica in reducing the negative effects of freeze-thaw cycles on the soil characteristics. Finally, to identify the underlying improvement mechanisms, the microstructural analyses were also carried out on different soil samples by using the X-Ray Diffraction (XRD) and Scanning Electron Microscopy (SEM) tests.

The influence of amylose and amylopectin on water retention capacity and texture properties of frozen-thawed konjac glucomannan gel

As freeze-thaw processing has become an emerging way to regulate the texture properties of the konjac glucomannan (KGM), the freezing-induced syneresis is getting increased concern in the food industry. In this study, the effects of the different types' starches (amylose and amylopectin) and the frozen conditions on the water retention capacity and texture properties of the frozen KGM-Starch blended gel (KS gel) were investigated. Comparing the effects of the subzero conditions and the starches on the blended gel, we found that the latter would be more powerful to affect the syneresis rate and water holding capacity of the frozen KGM gel, and a dense porous network microstructure emerged in the frozen KS gels. Research results also showed that the water holding capacity of the frozen KS gels could be significantly improved for the increased starches content, while their syneresis rate could be lowered significantly (p < 0.05). Besides, the KGM-amylose blended gel showed a greater value of hardness and chewiness than that of the KGM-amylopectin blended gel after being subjected to the same frozen condition. While even though no significant difference in the SR could be observed between the KGM blended gels treated with the different frozen conditions (frozen time, subzero temperature, and the number of freeze-thaw cycles), a noticeable change in their texture properties could still be detected. What's more, results showed that starch types and concentrations would profoundly affect the proportion of water at different states in the KGM blended gels. These results suggest that the frozen-thawed stability of the KGM gel could be improved by adding in the different types of starch, which may provide some guidance for the production of frozen KGM gel food.

Effect of freeze-thaw cycles on the physical and dynamic characteristic of modified Na-bentonite by KCl

The method of electrokinetic ion-exchange–modified bentonite can not only shorten the test period but also improve the efficiency of cation exchange. In this study, the X-ray fluorescence spectroscopy test, freeze-thaw (FT) cycle test, CT scan test, and dynamic triaxial test were performed on bentonite before and after modification. The results showed that cation exchange occurred between the bentonite layers and the free expansion rate was significantly reduced. With the increase in the number of FT cycles, the Na-bentonite samples did not change significantly, while the K-bentonite gradually appeared cracks, and the cracks developed significantly as the number of FT cycles increased. The FT cycles had a significant impact on the dynamic parameters of two bentonites, especially the first two FT cycles. When the strain was constant, the dynamic shear modulus of the two bentonites decreased first and then increased with the increase of the number of FT cycles, and then tended to be stable. The damping ratios of the two bentonites showed the opposite trend: the damping ratio of the Na-bentonite increased first and then decreased with the increase of the FT cycles, and the K-bentonite first decreased, then increased and then stabilized, indicating that the structure of K-bentonite was more stable. By comparison, it was found that the effects of FT cycles on the dynamic parameters of K-bentonite were smaller than those of Na-bentonite.

Mechanical properties of rock samples with a single natural weak plane after freeze-thaw action

The freeze-thaw cycle test and uniaxial/triaxial compression test were carried out on sandstone specimens with different structural plane angles, and the variation of sandstone strength with the structural plane angle of a single-group structural plane was studied. The results show that the strength variation law established by the single discontinuity theory is in good agreement with the uniaxial and triaxial test results, and that these can correctly reflect the strength variation law of sandstone. Under a certain cell pressure, the sandstone strength declines with the number of freeze-thaw cycles. Under a certain number of freeze-thaw cycles, the sandstone strength improves with the cell pressure. The strength difference of rock samples with different structural plane angles decreases with the cell pressure and freeze-thaw cycles. Sample failure modes vary with the structural plane angles. When 0° ≤ α ≤ α1, the rock sample undergoes splitting tension failure through the matrix and bedding plane, with a few shear cracks. When α1 ≤ α ≤ α2, the shear failure of sandstone occurs only along the structural plane. When α2 ≤ α ≤ 90°, the splitting failure of the rock sample occurs along the axis direction.

Freeze-thaw resistance of recycled aggregate concrete damaged by simulated acid rain

Acid rain severely decreases the durability of ordinary concrete structures; however, the effect of acid rain on recycled aggregate concrete (RAC) remains unclear. To fill this gap, this study investigated the freeze-thaw resistance of RAC in response to simulated acid rain spraying. The effects of replacement ratios of recycled coarse aggregate (20%, 35%, and 50% by mass), acidity of simulated solutions (pH of 2.5 and 3.5), erosion time (0, 20 d, and 40 d), and the number of freeze-thaw cycles on the apparent state, quality loss, and relative dynamic elastic modulus (RDEM) of RAC were evaluated. The results demonstrate that the freeze-thaw resistance of RAC with different replacement ratios is unsatisfactory in comparison to ordinary concrete. Acid rain attack has no obvious effect on the mass loss rate of RAC, but it significantly influences the RDEM. The RDEM results indicate that acid rain attack weakens the capacity of RAC to resist freezing and thawing. Moreover, the freeze-thaw resistance of RAC decreases strongly with prolonged acid rain spraying time or with increased acidity of acid rain. These test results indicate several theoretical suggestions and potential implications for government and industry to increase energy conservation, pollution reduction, and recycling of resources.

Effects of freeze-thaw on dissolved nitrogen pool, nitrogen transformation processes and diversity of bacterial community in temperate soils

Soil freeze-thaw could affect nitrogen (N) availability. The N transformation is closely related with soil microbes. The effect of soil freeze-thaw on the soil bacterial communities in the temperate zone is still not clear. We hypothesized that freeze-thaw events could affect the diversity and composition of bacterial communities, thereby changing the contents of soil dissolved nitrogen pools as well as the N transformation process. In this study, microcosms with different freeze-thaw cycles (six and fifteen cycles) were designed, with the constant temperature at 2 ℃ as the control. The results showed that the contents of dissolved total nitrogen, dissolved inorganic nitrogen, microbial biomass nitrogen and net nitrogen mineralization rate were decreased significantly in response to increasing cycles of freeze-thaw. The number of freeze-thaw cycles did not affect bacterial α diversity. In contrast, the duration of incubation was positively correlated with bacterial α diversity including Chao1 and Shannon indices. Freeze-thaw treatment significantly affected the function and composition of bacterial communities, but the number of freeze-thaw cycles had little effect on the bacterial community structure. The partial redundant analysis showed that under freeze-thaw treatments, both the composition and function of bacterial community were significantly related to soil dissolved N pools and N transformation processes.

Seismic behavior of frost-damaged squat RC shear walls under artificial climate environment: a further experimental research

In cold environment, the damage of freezing and thawing poses a great threat to the safety of concrete structures. In this study, six frost-damaged squat reinforced concrete (RC) shear walls were subjected to low cyclic reversal loading to investigate the effects of axial compression ratio, concrete strength and freeze-thaw cycles (FTCs) on the seismic performance of squat RC shear walls. The seismic behavior of the test specimens was evaluated in terms of the frost action at the microstructure level, frost-heave crack patterns, damage processes, failure patterns, hysteretic behaviors, skeleton curves, deformations, and energy dissipation capacities. It shows that the boundary elements and distributed reinforcements had obvious restraining effects on the development of frost-heave cracks. The FTC action weakened the load-carrying capacity, energy dissipation capacity, and shear resistance capacity of the walls. When the number of FTCs is kept at 200, with the increase of the concrete strength, the gel structure (C-S-H) gradually evolved from fibrous to nets, also the width and number of frost-heave cracks started to reduce, and the distribution of frost-heave cracks evolved from the middle of the specimen to the perimeter. Moreover, the energy dissipation capacity and the ratio of the shear displacement on the whole displacement after cracking loading condition started to increase.

Durability of Structural Recycled Aggregate Concrete Subjected to Freeze-Thaw Cycles

The increasing global demand for natural resources and the extensive production of construction and demolition waste (CDW) raise concerns for both the economic and environmental consequences that they can induce. Several efforts are being made with the aim to promote sustainable practices in the construction industry. In this context, one of the most relevant options refers to reusing CDW in new construction: specifically, the use of recycled concrete aggregate (RCA) is attracting a growing interest. Unfortunately, although the behavior of recycled aggregate concrete (RAC) has been widely investigated in the last few years, there are still knowledge gaps to fill on various aspects of the RAC performance, such as its durability in extreme conditions. The present study deals with the freeze-thaw performance of normal- (C35) and high-strength (C60) RAC produced with RCAs derived from different sources. Specifically, ten concrete mixtures were subjected to a different number of freeze-thaw cycles (namely, 0, 150 and 300), with the aim of analyzing the degradation of key physical and mechanical properties, such density, compressive strength, elastic modulus and tensile strength. Based on the obtained experimental results, a novel degradation law for freeze-thaw cycles is proposed: it unveils a relationship between open porosity of concrete, which is directly correlated to the peculiar properties of RCAs, and the corresponding damage level determined on RAC specimens.

A thermodynamics-based model for freeze-thaw damage in asphalt mixtures

Damage due to freeze-thaw cycles is a major problem for asphalt mixtures. Considering the complexity of the damage process in asphalt mixtures, characterization of the process and its effect on the material behavior is not straightforward. This paper therefore develops a thermodynamics-based model which includes viscoelasticity, damage due to freeze-thaw cycles, and temperature dependent damage due to external forces which affects the elastic strain energy. Furthermore, the model couples the freeze-thaw damage and the damage due to external forces in order to capture the aggravating effect that they have on each other in reality. The freeze-thaw damage evolution is in the model dependent on the number of freeze-thaw cycles and the duration of the freezing in each cycle. The novelty of the model, the freeze-thaw damage and its coupling to the elastic energy damage, is highlighted through numerical examples. It is shown that the model is capable of simulating an increase of the freeze-thaw damage through several freeze-thaw cycles and a realistic deteriorating effect on the material properties which is consistent with reported results from previous studies. Furthermore, the effect of coupling the two damages is illustrated by comparing the effect of the resulting damage to an uncoupled case.

Development of a certified genomic DNA reference material for detection and quantification of genetically modified rice KMD.

Qualitative and quantitative detection of genetically modified products is inseparable from the application of reference materials (RMs). In this study, a batch of genomic DNA (gDNA) certified reference materials (CRMs) was developed using genetically modified rice Kemingdao (KMD) homozygotes as the raw material. The gDNA CRMs in this batch showed good homogeneity; the minimum sample intake was determined to be 2μL. The stability study showed that transportation by cold chain is preferable, no significant degradation trend was observed during a 12-month period when storing the gDNA CRMs at 4°C and - 20°C, and the number of freeze-thaw cycles cannot exceed 10. The property values of the copy number ratio of transgene and endogenous gene and the copy number concentration for gDNA CRMs were determined by a collaborative characterization of eight laboratories using the duplex KMD/PLD droplet digital PCR (ddPCR) assays. The uncertainty components of characterization, potential between-unit heterogeneity, and potential degradation during long-term storage were combined to estimate the expanded uncertainty of the certified value with a coverage factor k of 2.0. The certified value of copy number ratio for KMD gDNA CRM is 0.99 ± 0.05, and that of copy number concentration is (1.76 ± 0.10) × 105 copies/μL. Compared to the gDNA CRMs in availability, this batch of KMD gDNA CRMs is assigned accurate property values and can be directly used for qualitative and quantitative detection of GMOs as well as evaluation of the parameters of analytical methods with no need of further DNA concentration measurement. Graphical abstract.

Studies on Extraction and Stability of C-Phycoerythrin From a Marine Cyanobacterium

Being naturally produced colorants with fluorescent properties, phycobiliproteins (PBPs) have important food industry applications. However, optimization of extraction and their stability under storage is an aspect which needs further attention. In this study, optimization of phycobiliprotein extraction from Lyngbya sp. CCNM 2053 was undertaken using response surface methodology (RSM). Preliminary screening suggested a phosphate buffered system with freeze thaw for cell disruption as the most suitable method. 22.40 ± 1.31 mg g-1 C-phycoerythrin (CPE) and 52.76 ± 0.07 mg g-1 total proteins were extracted using phosphate buffer while freeze thaw method yielded 19.87 ± 0.43 mg g-1 CPE and 58.92 ± 3.49 mg g-1 total proteins. RSM was used to optimize phosphate buffer pH (5.5 - 8), molarity (0.1 - 1 M) and number of freeze thaw cycles (2 - 7). Interaction between buffer molarity and number of freeze thaw cycles was most significant for modelling the responses. Extraction of phycobiliproteins was highest with pH 8 and low molarity buffers. The predicted values from the equations agreed well with the experimental values, proving the robustness of the model. The stability of the extract was also evaluated at different temperatures, light exposure times and pH values. Results indicated that light exposure should be kept to a minimum while the stability was affected by extreme temperatures and pH. CPE was comparatively stable in a pH and temperature range of 3 – 8 and 4 – 40 °C respectively.

Durability Performances of Aramid Fiber Reinforced Polymer as Reinforcement Material for Concrete Structures in Cold Regions

A series of tests were conducted to investigate the mechanical performances of aramid fiber reinforced polymer (AFRP) and its epoxy resin matrix after 0, 20, 40, 60 and 80 freeze-thaw cycles in the dry air, respectively. After a given number of freeze-thaw cycles, the residual tensile strength and elastic modulus of AFRP specimens were measured, and the lap-shear strength of epoxy resin adhesive specimens was gained. Test results show that: (1) Variation of the elastic modulus of AFRP with the increasing of the freeze-thaw cycles exhibits the same tendency as the tensile strength did. They increase in the first 20 to 40 cycles and then decrease till the end of 80 cycles; (2) The tensile strength and elastic modulus of AFRP decreases by 5.1% and 8.2%, respectively, after 80 cycles as compared with that kept in the laboratory environments. However, the effect of the freeze-thaw cycling in the dry air on the tensile properties of CFRP is very limited within 80 cycles; (3) The freeze-thaw cycling in the dry air of this study has an adverse effect on the adhesive property of the epoxy resin, which could be regarded as the evidence for the degradation of the interface between aramid/carbon fiber and matrix.