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Tensile Properties Analysis Of 3D Flat-Knitted Inlay Fabric Reinforced Composites Using Acoustic Emission

Publicado en línea: 07 Jan 2020
Volumen & Edición: AHEAD OF PRINT
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Detalles de la revista
License
Formato
Revista
eISSN
2300-0929
Primera edición
19 Oct 2012
Calendario de la edición
4 veces al año
Idiomas
Inglés
Abstract

In this work, based on the quasi-static tensile test and acoustic emission technology, the tensile properties of two types of three-dimensional flat-knitted inlay fabrics reinforced composites are investigated, and the acoustic emission characteristic parameters of various damage mechanisms are obtained. The transverse tensile process of specimens could be divided into the elastic stage, yield stage, and fracture stage. We found that, compared with the fluctuation of the stress-strain curve in the yield stage, weft insertion yarns in composite with interlock structure broke almost simultaneously, while the composite with plain stitch broke successively. The transverse and longitudinal tensile strength of the composite with interlock structure was 44.70% and 28.63% higher than the composite with plain structure, respectively. The SEM micrographs showed that the damage mechanism of the composites was matrix fracture, fiber-matrix debonding, and fiber breakage. The amplitude ranges of the three damage mechanisms were 50–65 dB, 65–80 dB, and 90–100 dB, respectively, and the frequency ranges were 35–114 kHz, 116–187 kHz, and 252–281 kHz, respectively. Fiber-matrix debonding and matrix fracture had large cumulative AE energy, numerous events, and long duration time, while fiber breakage had the characteristics of large amplitude, high frequency, low cumulative AE energy, few events, and short duration time.

Keywords

Introduction

In recent years, research and engineering interest have been shifting on the polymer composites with knitted fabric as reinforcement, due to its attractive properties in rapidly forming, good forming quality, and low artificial participation [15]. Attempts have been made to reduce the processing cost of composite products with complex shapes and structures using knitted fabrics as preforms. So far, automobile components [6, 7], wind turbine blades [810], and helmet shells [11] are now being manufactured using knitted fabric reinforced composites. The excellent bending and drapability of knitted fabrics bring the outstanding advantages of formability and bring the disadvantages of low in-plane strength and stiffness of knitted fabric reinforced composites [12]. However, the above disadvantages can be solved by using inlay yarn [13, 14]. For these reasons, warp-knitted axial fabric-reinforced composites are widely used in wind turbine blades, and multi-layer biaxial weft-knitted composites have been successfully used in pilot helmets, aircraft wings cover, car bodies, and other products.

Three-dimensional flat-knitted inlay (3DFKI) fabric is a knitted fabric with non-buckling reinforcement yarn. Compared with biaxial weft-knitted fabric, the 3DFKI fabric is a uniaxial three-dimensional flat-knitted fabric. Biaxial weft knitted fabric is usually produced on the modified double needle bed flat knitting machine [15, 16]. Although the fabric has outstanding mechanical properties in the transverse and longitudinal directions, it is difficult to directly produce preforms with special shaped structures and complex shapes due to longitudinal reinforcing yarn. Therefore, it is often necessary to prepare composite products with complex shapes by cutting and pressing methods. The 3DFKI fabric is made by adding weft insertion yarns in the 3D flat-knitted fabric, which can be easily realized on the conventional computer flat knitting machine, and the local knitting technology can be used to realize the integral forming of the preform with complex shape and structure. Thus, 3DFKI fabric-reinforced composites not only have good mechanical properties, but also have the advantages of good formability, low processing cost, fast production speed, and a short preparation process. It has excellent development potential in transportation, personal protection, medical devices, and other industrial fields.

The tensile test is the most critical test method to describe the mechanical properties of composites and obtain their basic mechanical properties [1719]. The basic mechanical properties such as the tensile load, stress and strain, tensile modulus, and Poisson’s ratio can be obtained by a tensile test, which can guide the actual production and application and evaluate and predict the mechanical properties of products. However, the tensile test can measure only the change of external force during the failure process of the composite, and it provides minimal information on damage evolution and expansion [20, 21]. In addition, the structure of textile composites is complex and anisotropic, and different damage mechanisms are activated at the same time [22]. Consequently, the damage process of textile composites is very complex. In order to reveal the damage accumulation process of composites, in recent years, the failure mechanism of composites has been analyzed based on ultrasonic inspection [23, 24], thermography [25, 26], X-ray [27, 28], and acoustic emission (AE) [29, 30]. AE is a dynamic monitoring method that can detect the damage process of composites under load in real time and has functions such as damage detection, damage location, and damage identification [31, 32]. The working principle of AE is to connect the sensor to the sample, continuously record real-time data during the dynamic damage process of the sample, use advanced data analysis for feature extraction, link the observation data with the damage state, and determine the damage form and damage location of the sample [33]. In a review paper published recently by Milad et al., the research progress of AE in damage detection and damage identification of composites was analyzed in detail and comprehensively [34]. It is worth noting that there was more literature on glass fiber, carbon fiber, and aramid fiber reinforced composites and less literature on ultrahigh molecular weight polyethylene (UHMWPE) composites. UHMWPE fibers have attracted the most attention, since their strength exceeds that of carbon and aramid fibers [35]. Compared with other high-performance fibers, UHMWPE fiber not only has high strength and modulus along the fiber axis, but also has the characteristics of low density (0.97 g/cm3) and good knitting ability. To the best of our knowledge, the literature on the use of AE technology to study the tensile properties of UHMWPE knitted composites has not yet been reported.

The present paper prepared two types of 3DFKI fabric reinforced composites using UHMWPE yarn. Two composites obtained were subjected to a quasi-static tensile test, and the influence of the fabric structure on its tensile properties was compared and analyzed. Moreover, the tensile tests were monitored by acoustic emission. The main objective was to correlate the damage mechanism with the AE signal, and determine the characteristics of the AE signal of the damage mechanism.

Experimental
Materials and 3DFKI fabric fabrication

The UHMWPE filaments studied were purchased from Hangzhou Xiangsheng high strength fiber material Co., Ltd., Hangzhou, China. The specifications of knitting yarn and weft insertion yarn are shown in Table 1. A01 epoxy resin and B02 hardener were provided by Hualike New Material Co. LTD, Changzhou, China.

Performance parameters of the knitting yarns and weft insertion yarns

Type Fineness/denier Diameter/mm Density/g·cm-3 Tensile strength/MPa Tensile modulus/Gpa
Knitting yarns 600 0.30 0.97 2,419 90
Weft insertion yarns 1,000 0.38 2,707 93

3DFKI fabrics of two structures were prepared on the KSC-132D computer flat knitting machine (Gauge E14, Longxing, China). The knitting steps and structures of two types of fabrics (named Fabric I, Fabric II) are presented in Figures 1 and 2, respectively. The corresponding specifications of the two types of 3DFKI fabrics are shown in Table 2. Fabric I was a 3DFKI fabric that combines interlock structure, tuck stitch, and weft insertion yarns. Fabric II was a 3DFKI fabric with a plain stitch, a tuck stitch, and weft insertion yarn. The interlock structure in Fabric I belonged to double-sided fabric, and the knitting yarn ran through the upper and lower surfaces of the whole fabric, formed a three-dimensional structure with good integrity. The upper and lower surface fabrics of Fabric II were independent of each other, which were connected through the internal tuck stitch, thus forming a three-dimensional spacer structure. Therefore, the thickness of Fabric II was slightly larger.

Figure 1.

Knitting steps of two types of 3DFKI fabrics: (a) Fabric I and (b) Fabric II

Figure 2.

Structures of two types of 3DFKI fabrics: (a) Fabric I and (b) Fabric II

Specifications of two types of 3DFKI fabrics

Sample Density Thickness/mm Areal density/g·m-2
Course/wales·5cm-1 Wale/courses·5cm-1
Fabric I 28 39 1.96 808
Fabric II 2.18 824
Preparation of 3DFKI fabric reinforced composites

The vacuum-assisted resin infusion (VARI) and external pressure methods were used to prepare composite plates with the same thickness. Figure 3 shows the mold structure and composite preparation process. The specific operation process can be divided into four steps: in the first step, place a layer of demolding cloth, guide net, and vacuum film on the lower plate of the mold, then cover the upper plate, zero the four dial indicators, and then remove the upper plate. In the second step, the fabric, demolding cloth, guide net, and vacuum film are stacked together in sequence after applying demolding wax on the lower plate of the mold, and the vacuum film is sealed with sealant. In the third step, the mixed resin solution is injected under the vacuum pump pressure of 0.08 Mpa, and then the next step is carried out after the sealing performance was good. In the fourth step, cover the upper plate, and adjust the four dial indicators to 1.80 mm by adjusting the four bolts of the upper plate. The indication of the dial indicator is the thickness of the composite plate. The demolding operation was carried out after curing. The mixed resin solution was composed of A01 and B02 with a mass ratio of 2:1. The curing conditions were 5 h at 50°C and 24 h at room temperature. The resin casting was prepared by rubber mold, and the curing condition was the same as that of the composite. The parameters of the 3DFKI fabric reinforced composites (named C-I, C-II) and resin casting are shown in Table 3.

Figure 3.

Preparation of 3DFKI fabric reinforced composites

Specifications of 3DFKI fabric reinforced composites and resin casting

Sample Reinforced fabric Thickness/mm Density/g·cm-3 Fiber volume fraction/%
C-I Fabric I 1.80 0.95 46.28
C-II Fabric II 1.04 47.19
Resin casting - 3.50 1.13 -
Tensile test

Tensile experiments of 3DFKI fabric reinforced composites were conducted on a UTM5105 electronic universal testing machine at room temperature with a constant loading velocity of 10 mm/min according to the standard of GB/T 1447-2005. The sample size was 180 mm × 20 mm, the gauge distance was 50 mm, and the sample shape and size are shown in Figure 4. Five samples for each specification were used for the test.

Figure 4.

Shape and size of the tensile test sample.

Acoustic emission test was carried out according to ASTM E2478-11. Double channel DS5 full information AE signal analyzer manufactured by Beijing Soft Island Times Technology Co., Ltd. was used for the analysis. During the tensile test, the collected AE signals were processed by the system software to obtain the data of action time, amplitude, energy, and peak frequency. Figure 5 shows the schematic diagram of the AE testing system.

Figure 5.

Schematic diagram of the AE testing system

Results and discussion
Tensile behavior of composites

The tensile stress-strain curves and parameters of the two composites are shown in Figure 6(a)–(c). It can be seen from Figure 6(a) that the transverse stress-strain curves of the two composites can be divided into three stages. The first stage was the elastic stage, where the stress and the strain were in an apparent linear relationship, and the stress increased with the increase of strain. At this stage, due to the small strain, the knitting yarn in the fabric was still in a bent state, and the resin matrix and the weft insertion yarn bore the tensile load together. With the increase of load and tensile deformation, the weft insertion yarn gradually bore the main load, giving full play to the performance of the non-buckling reinforcing yarn. The second stage was the yield stage, in which the stress began to decrease slightly after reaching the peak value, the linear relationship between stress and strain was destroyed, and the stress fluctuated with the increase of strain. These characteristics were more evident in the tensile curve of C-II-0°. In this stage, the weft insertion yarn continued to bear the external load. It could be inferred from the fluctuation of the stress that the weft insertion yarn began to break. Compared with C-II, the peak force of C-I in the yield stage was higher, and the duration was shorter. This indicates that the weft insertion yarn of C-I broke almost simultaneously under the external load, while the weft insertion yarn of C-II broke successively. The third stage was the failure stage. The stress dropped sharply and remained at a certain height, which indicates that the weft insertion yarn inside the composite had completely failed, and the knitting yarn began to bear the external force. With the increase of strain, the stress remained in a high range and fluctuated continuously, which indicates that the knitting yarn inside the composite was gradually destroyed. When the composite was stretched longitudinally, it mainly bore the external force through the loop pillar [36]. Therefore, the longitudinal stress-strain curves of the two composites were relatively simple.

Figure 6.

Tensile properties of two composites: (a) Stress-strain curves, (b) Tensile strength, (c) Tensile modulus. (0°-transverse stretch, 90°-longitudinal stretch. The data in the column are the mean ± standard deviation)

Figure 6(b)–(c) shows the tensile strength and modulus of the two composites. The tensile strength and modulus of composites depend on fiber volume content, component materials, and reinforcement structure [17]. It could be seen that the transverse tensile strength and modulus of the two composites were much higher than their longitudinal tensile strength due to the addition of weft insertion yarns. Notably, although the fiber volume content of C-I was slightly lower than that of C-II, the transverse tensile strength of the former was 44.70% higher than that of the latter. Compared with C-II with the spacer structure, the interlock structure in C-I with better integrity had a noticeable binding effect on the weft insertion yarn, which made the force of the weft insertion yarn more balanced. In addition, it could be seen from the cross-section diagram of two fabrics in Figure 2 that there were more contact points between the basic structure of Fabric I and the weft insertion yarn. Contact points increased the friction resistance to the weft insertion yarn during the tensile process, and also helped to improve the force uniformity and consistency of the weft insertion yarn at different positions. This is also why the elongation at the break of C-I was about 51.12% higher than that of C-II. Since the wale density of the two fabrics was the same and the number of weft insertion yarns inside the fabric was the same, the transverse modulus of the two composite materials was similar. Moreover, we compared the longitudinal tensile properties of the two composites, and it was found that the longitudinal tensile strength and modulus of C-I were 28.63% and 41.85% higher than that of C-II, respectively. The tensile properties of composites mainly depended on the mechanical properties of reinforced fabrics. It could be seen from the cross-sectional structure of the fabric that the difference between the two types of fabrics was that the interlock loops inside Fabric I were overlapped with each other, while the plain stitch loops inside Fabric II were independent on both sides of the fabric. It is because of this compact structure that the tensile properties of C-I were higher.

Tensile damage and fracture mechanism

The tensile damage morphology of composites is shown in Figure 7. SEM micrographs of the specimen after tensile failure are presented in Figure 8. It can be seen in Figure 8 that there were three damage mechanisms of matrix fractures, fiber-matrix debonding, and fiber breakage. Among them, matrix fractures and fiber-matrix debonding were the primary failure mechanism. The fracture morphology of the two composites in the same loading direction was similar, as shown in Figure 7. The damage morphology after transverse tensile failure had the characteristics of a long fracture area and no clear fracture, while the longitudinal direction had a clear and concentrated fracture. Before the tensile fracture of fabric-reinforced composites, the yarns supported the main load, so the damage morphology of the sample was related to the state of the yarn in the fabric. In the longitudinal direction of the reinforced fabric, there was the only yarn with coil structure, and the structure was simple. In the tensile process, when the bending coil and the matrix broke, the sample failed, and the fracture was clear. At the same time, during the longitudinal stretching process, the loop pillar of the coil bore the main load and the deformation was small, so the fracture area was more concentrated. In the transverse direction of the reinforced fabric, there were not only the yarn with the coil structure but also the weft insertion yarn in the straight state. In the transverse stretch, the weft insertion yarn broke first, and then with the increase in strain, the knitting yarn broke, and the fabric structure was destroyed. When the knitting yarn broke, the needle loop arc and sinker loop arc were deformed larger, and the transverse tensile fracture area of the composite was longer. Additionally, due to the large transverse elongation of the basic structure, there were still some yarns that are not broken from tensile failure.

Figure 7.

Tensile damage morphology of two composites: (a) C-I-0°, (b) C-I-90°, (c) C-II-0°, (d) C-II-90°

Figure 8.

SEM micrographs of the specimen after tensile failure

Acoustic emission analysis

Figure 9 exhibits the load and amplitude versus time for composites and resin casting. The parameter characteristics of two types of composites in transverse tension are shown in Figures 9(a) and (c). It could be seen that the AE signal was mainly concentrated between 50-80 dB in the elastic stage of tension, and the primary damage mechanism in this stage was matrix fractures and fiber-matrix debonding. With the increase in load and time, the AE signal increased gradually, indicating that the damage was aggravated. In the yield stage, the amplitude of the AE signal was 50–100 dB, which contained a small amount of high amplitude AE signal (90–100 dB). This indicates that in addition to matrix fractures and fiber-matrix debonding, fiber breakage also occurred in the composites. The amplitude range of UHMWPE fiber breakage was consistent with the reference [37]. There was no damage on the surface of the two composites in the actual tensile process, because the fiber breakage at this stage was the breakage of the weft insertion yarn in the sample. The time and load of the first high amplitude AE signal of C-I were 53 s and 4,243 N, respectively, and the corresponding time and load of C-II were 34 s and 3,110 N, respectively. It could be seen that the starting time of weft insertion yarns of C-I was later than that of C-II, and had higher strength. This result shows that the tensile properties of C-I were better. In addition, the duration of the yield stage of C-I was 8 s, while that of C-II was 36 s, which again proved the fiber breakage in C-II did not occur simultaneously. In the failure stage, the range of the AE signal was also between 50–100 dB, indicating that damage mechanisms such as matrix fractures, fiber-matrix debonding, and fiber breakage coexist. However, the load at this stage was lower than that at the yield stage because the knot strength of the yarn was much lower than the tensile strength of the non-crimp yarn [38]. Therefore, the fiber breakage at this stage was caused by the fracture of the knitting yarn at the bending state. Figure 9(e) shows the tensile load and amplitude versus time for resin casting. It could be seen that the amplitude range of matrix fracture was 50–65 dB, so it could also be inferred that the fiber-matrix debonding was 65–80 dB. The number of AE signals in longitudinal tension was much lower than in transverse tension, as illustrated in Figures 9(b) and (d). This phenomenon was due to the simple structure of the fabric in the longitudinal direction, which was stressed by the loop pillar, so the deformation was small and the stretching process lasted for a short time. It could be seen that during the stretching process, the AE signal amplitude was mainly maintained at about 50 dB, and the number was small. Before the composite failed, the AE signal increased rapidly, and the high amplitude signals of 70–80 dB and 90–100 dB appeared.

Figure 9.

Load and amplitude versus time for composites and resin casting: (a) C-I-0°, (b) C-I-90°, (c) C-II-0°, (d) C-II-90°, (e) resin casting

In order to further explore the relationship between the damage mechanism and the dynamic response characteristics of AE signal, on the one hand, and distinguished and quantified various damage mechanisms, on the other, we took the transverse tension of C-I as an example. The feature extraction of AE signal data was carried out based on an advanced data analysis method. Based on the three main damage mechanisms observed in SEM micrographs, namely matrix fractures, fiber-matrix debonding, and fiber breakage, the AE signals were divided into three classes by K-Means clustering analysis. Figure 10 shows the clustering results of AE signals in the transverse tensile test of C-I. The peak frequency range of Class-1 was 35–114 kHz, showed low frequency; the peak frequency range of Class-2 was 116–187 kHz, presented intermediate frequency; the peak frequency range of Class-3 was 252–281 kHz, indicated as high frequency. From earlier studies, in the fabric reinforced composites, the frequency of matrix fractures was lower, the frequency of fiber breakage was the highest, and the frequency of fiber-matrix debonding was between the two frequencies [3941]. For 3DFKI fabric reinforced composites, Class-1 represented matrix fractures, Class-2 represented fiber-matrix debonding, and Class-3 represented fiber breakage. Table 4 shows the classification ratio of AE signals in the transverse tensile test of C-I. The data showed that the fiber-matrix debonding was the primary failure mode, accounting for 69.33%. This is mainly due to the poor interface bonding between the epoxy resin and UHMWPE [36]. The fiber breakage accounted for a minor proportion, and the matrix fractures were in the middle.

Figure 10.

Clustering results of AE signals in the transverse tensile test of C-I

Classification ratio of AE signals in the transverse tensile test of C-I

Classification Frequency range / kHz Number of AE signals Ratio / %
Class-1 35–114 178 25.87%
Class-2 116–187 477 69.33%
Class-3 252–281 33 4.80%

The increasing trend of AE signal could well reflect the dynamic damage evolution process of composites during loading [21]. AE energy is very sensitive to the initiation of damage, evolution, and ultimate failure of composites in tensile tests [22]. Figure 11 illustrates the various damage mechanism and the total cumulative AE energy versus time for C-I. There were three intervals (0–60 s, 60–156 s, 157–240 s) corresponding to the sharp increase of cumulative energy curve value. That the number of AE signals increased considerably indicates the occurrence of significant damage in the material. The reinforced fabric of C-I consisted of three structures, i.e., the weft insertion, tuck, and interlock stitch. From the yarn length of various structures, it could be judged that the weft insertion yarn broke first, followed by the tuck yarn, and finally the interlock yarn when the fabric stretched in the transverse direction. Therefore, we inferred that the 0–60 s corresponded to the weft insertion yarn fracture, the 60–156 s corresponded to tuck stitch fracture, and the 157–240 s corresponded to the interlock structure failure. It can also be seen in Figure 11 that the cumulative AE energy curves of fiber-matrix debonding and matrix fracture are consistent with the total cumulative AE energy curves, and the cumulative AE energy of the two damage mechanisms was much higher than that of fiber breakage. Table 5 shows the ratio of AE energy, AE events, and duration for the various damage mechanisms. It can be seen that matrix fracture and fiber-matrix debonding had the characteristics of large cumulative AE energy, numerous events, and long duration time, while fiber breakage was just the opposite.

Figure 11.

Various damage mechanisms and total cumulative AE energy versus time for C-I

Ratio of AE energy, AE events, and duration for various damage mechanisms

Damage mechanisms AE energy /mV·ms Ratio / % AE events Ratio / % AE signal duration / μs Ratio / %
Matrix fracture 62,531.46 47.47 24,904 26.23 732,729 37.75
F/M debonding 68,397.03 51.92 67,088 70.66 1,155,719 59.55
Fiber breakage 800.92 0.61 2,948 3.11 52,313.33 2.70
Total 131,729.41 100 94,940 100 1,940,761.06 100
Conclusions

For this paper, two types of 3DFKI fabric-reinforced composites were prepared using UHMWPE yarn, and the tensile properties of two composites were studied based on acoustic emission technology. The following conclusions can be summarized:

The transverse tensile process of two composites can be divided into the elastic, yield, and fracture stages. Compared with C-II, the stress-strain curve of C-I in the yield stage had the characteristics of small fluctuation, long duration, and large peak force, indicating that the weft insertion yarns of C-I broke almost simultaneously, while the weft insertion yarn of C-II broke successively.

The transverse tensile strength and modulus of the composites were greatly improved due to the addition of weft insertion yarns. The structure of the reinforced fabric had a significant effect on the tensile properties of the composites. The longitudinal tensile strength and modulus of C-I were 28.63% and 41.85% higher than that of C-II, respectively. Due to the fact that the interlock structure had a more prominent binding effect on the weft insertion yarn, the transverse tensile strength of C-I was 44.70% higher than that of C-II.

The amplitude ranges of matrix fracture, fiber-matrix debonding, and fiber breakage were 50–65 dB, 65–80 dB, 90–100 dB, respectively, and the frequency ranges were 35–114 kHz, 116–187 kHz, and 252–281 kHz, respectively. Fiber-matrix debonding and matrix fracture had large cumulative AE energy, numerous events, and long duration time, while fiber breakage had the characteristics of large amplitude, high frequency, low cumulative AE energy, few events, and short duration time.

The 3DFKI fabric-reinforced composites with interlock structure have better tensile properties. When we combine it with the forming technology of flat knitting, it is possible to develop knitted composites with excellent mechanical properties and complex shapes. In addition, acoustic emission characteristic parameters of different damage mechanisms of UHMWPE knitted composites can provide a reference for damage detection and damage identification of wind turbine blades, storage tanks and other products.

Figure 1.

Knitting steps of two types of 3DFKI fabrics: (a) Fabric I and (b) Fabric II
Knitting steps of two types of 3DFKI fabrics: (a) Fabric I and (b) Fabric II

Figure 2.

Structures of two types of 3DFKI fabrics: (a) Fabric I and (b) Fabric II
Structures of two types of 3DFKI fabrics: (a) Fabric I and (b) Fabric II

Figure 3.

Preparation of 3DFKI fabric reinforced composites
Preparation of 3DFKI fabric reinforced composites

Figure 4.

Shape and size of the tensile test sample.
Shape and size of the tensile test sample.

Figure 5.

Schematic diagram of the AE testing system
Schematic diagram of the AE testing system

Figure 6.

Tensile properties of two composites: (a) Stress-strain curves, (b) Tensile strength, (c) Tensile modulus. (0°-transverse stretch, 90°-longitudinal stretch. The data in the column are the mean ± standard deviation)
Tensile properties of two composites: (a) Stress-strain curves, (b) Tensile strength, (c) Tensile modulus. (0°-transverse stretch, 90°-longitudinal stretch. The data in the column are the mean ± standard deviation)

Figure 7.

Tensile damage morphology of two composites: (a) C-I-0°, (b) C-I-90°, (c) C-II-0°, (d) C-II-90°
Tensile damage morphology of two composites: (a) C-I-0°, (b) C-I-90°, (c) C-II-0°, (d) C-II-90°

Figure 8.

SEM micrographs of the specimen after tensile failure
SEM micrographs of the specimen after tensile failure

Figure 9.

Load and amplitude versus time for composites and resin casting: (a) C-I-0°, (b) C-I-90°, (c) C-II-0°, (d) C-II-90°, (e) resin casting
Load and amplitude versus time for composites and resin casting: (a) C-I-0°, (b) C-I-90°, (c) C-II-0°, (d) C-II-90°, (e) resin casting

Figure 10.

Clustering results of AE signals in the transverse tensile test of C-I
Clustering results of AE signals in the transverse tensile test of C-I

Figure 11.

Various damage mechanisms and total cumulative AE energy versus time for C-I
Various damage mechanisms and total cumulative AE energy versus time for C-I

Classification ratio of AE signals in the transverse tensile test of C-I

Classification Frequency range / kHz Number of AE signals Ratio / %
Class-1 35–114 178 25.87%
Class-2 116–187 477 69.33%
Class-3 252–281 33 4.80%

Performance parameters of the knitting yarns and weft insertion yarns

Type Fineness/denier Diameter/mm Density/g·cm-3 Tensile strength/MPa Tensile modulus/Gpa
Knitting yarns 600 0.30 0.97 2,419 90
Weft insertion yarns 1,000 0.38 2,707 93

Specifications of two types of 3DFKI fabrics

Sample Density Thickness/mm Areal density/g·m-2
Course/wales·5cm-1 Wale/courses·5cm-1
Fabric I 28 39 1.96 808
Fabric II 2.18 824

Ratio of AE energy, AE events, and duration for various damage mechanisms

Damage mechanisms AE energy /mV·ms Ratio / % AE events Ratio / % AE signal duration / μs Ratio / %
Matrix fracture 62,531.46 47.47 24,904 26.23 732,729 37.75
F/M debonding 68,397.03 51.92 67,088 70.66 1,155,719 59.55
Fiber breakage 800.92 0.61 2,948 3.11 52,313.33 2.70
Total 131,729.41 100 94,940 100 1,940,761.06 100

Specifications of 3DFKI fabric reinforced composites and resin casting

Sample Reinforced fabric Thickness/mm Density/g·cm-3 Fiber volume fraction/%
C-I Fabric I 1.80 0.95 46.28
C-II Fabric II 1.04 47.19
Resin casting - 3.50 1.13 -

Sun, Y. X., Lyu, L. H., Yan, B., Jiang, G. M., Ma, P. B. (2021). Preparation and characterization of 3D flexible high-distance spacer fabric/foam composite. Composite Structures, 26, 113,549. Sun Y. X. Lyu L. H. Yan B. Jiang G. M. Ma P. B. 2021 Preparation and characterization of 3D flexible high-distance spacer fabric/foam composite Composite Structures 26 113,549 10.1016/j.compstruct.2021.113549 Search in Google Scholar

Azadian, M., Hasani, H., Shokrieh, M. M. (2018). Low velocity impact behavior of 3D hollow core sandwich composites produced with flat-knitted spacer fabrics. Fibers and Polymers, 19(12), 2,581-2,589. Azadian M. Hasani H. Shokrieh M. M. 2018 Low velocity impact behavior of 3D hollow core sandwich composites produced with flat-knitted spacer fabrics Fibers and Polymers 19 12 2,581 2,589 10.1007/s12221-018-8368-8 Search in Google Scholar

Li, X. K., Bai, S. L. (2009). Sheet forming of the multi-layered biaxial weft knitted fabric reinforcement. Part I: On hemispherical surfaces. Composites Part A: Applied Science and Manufacturing, 40(6), 766-777. Li X. K. Bai S. L. 2009 Sheet forming of the multi-layered biaxial weft knitted fabric reinforcement. Part I: On hemispherical surfaces Composites Part A: Applied Science and Manufacturing 40 6 766 777 10.1016/j.compositesa.2009.03.007 Search in Google Scholar

Hassanzadeh, S., Hasani, H., Zarrebini, M. (2018). Mechanical characterization of innovative 3D multi-cell thermoset composites produced with weft-knitted spacer fabrics. Composite Structures, 184(1), 935-949. Hassanzadeh S. Hasani H. Zarrebini M. 2018 Mechanical characterization of innovative 3D multi-cell thermoset composites produced with weft-knitted spacer fabrics Composite Structures 184 1 935 949 10.1016/j.compstruct.2017.10.048 Search in Google Scholar

Li, X. Y., Yu, S., Ma, P. B., Jiang, G. M., Cong, H. L. (2019). Compression property of curved three-dimensional flat-knitted spacer fabric composites under quasi-static loading. Fibers and Polymers, 20(9), 2,002-2,007. Li X. Y. Yu S. Ma P. B. Jiang G. M. Cong H. L. 2019 Compression property of curved three-dimensional flat-knitted spacer fabric composites under quasi-static loading Fibers and Polymers 20 9 2,002 2,007 10.1007/s12221-019-9185-4 Search in Google Scholar

Van, V., Aart, W., Ko, F. K., Beevers, C. (2003). Net-shape knitting for complex composite preforms. Textile Research Journal, 73(1), 1-10. Van V. Aart W. Ko F. K. Beevers C. 2003 Net-shape knitting for complex composite preforms Textile Research Journal 73 1 1 10 10.1177/004051750307300101 Search in Google Scholar

Cherif, C., Krzywinski, S., Diestel, O., Schulz, C., Lin, H., Klug, P., Trumper, W. (2012). Development of a process chain for the realization of multilayer weft knitted fabrics showing complex 2D/3D geometries for composite applications. Textile Research Journal, 82(12), 1,195-1,210. Cherif C. Krzywinski S. Diestel O. Schulz C. Lin H. Klug P. Trumper W. 2012 Development of a process chain for the realization of multilayer weft knitted fabrics showing complex 2D/3D geometries for composite applications Textile Research Journal 82 12 1,195 1,210 10.1177/0040517511429602 Search in Google Scholar

Wu, Z. Y., Tie, L. (2011). The application of multi-axial warp knitted fabrics in wind turbine blade. Advanced Materials Research, 295, 46-50. Wu Z. Y. Tie L. 2011 The application of multi-axial warp knitted fabrics in wind turbine blade Advanced Materials Research 295 46 50 10.4028/www.scientific.net/AMR.295-297.46 Search in Google Scholar

Zangenberg, J., Brondsted, P., Koefoed, M. (2014). Design of a fibrous composite preform for wind turbine rotor blades. Materials and Design, 56(4), 635-641. Zangenberg J. Brondsted P. Koefoed M. 2014 Design of a fibrous composite preform for wind turbine rotor blades Materials and Design 56 4 635 641 10.1016/j.matdes.2013.11.036 Search in Google Scholar

Gao, Z., Ma, P. B., Jiang, G. M., Cong, H. L. (2016). Experimental investigation on the quasi-static penetration behavior of curved multi-axial warp-knitted composites. Fibers and Polymers, 17(9), 1,497-1,504. Gao Z. Ma P. B. Jiang G. M. Cong H. L. 2016 Experimental investigation on the quasi-static penetration behavior of curved multi-axial warp-knitted composites Fibers and Polymers 17 9 1,497 1,504 10.1007/s12221-016-6068-9 Search in Google Scholar

Xiang, H., Jiang, Y. M., Qi, Y. X., Li, J. L. (2020). Process-induced distortions characterization of MBWK fabric reinforced composite helmet shell. Materials, 13(3), 2,983. Xiang H. Jiang Y. M. Qi Y. X. Li J. L. 2020 Process-induced distortions characterization of MBWK fabric reinforced composite helmet shell Materials 13 3 2,983 10.3390/ma13132983 Search in Google Scholar

Muralidhar, B. A. (2013). Tensile and compressive behaviour of multilayer flax-rib knitted preform reinforced epoxy composites. Materials and Design, 49(8), 400-405. Muralidhar B. A. 2013 Tensile and compressive behaviour of multilayer flax-rib knitted preform reinforced epoxy composites Materials and Design 49 8 400 405 10.1016/j.matdes.2012.12.040 Search in Google Scholar

Abounaim, M., Diestel, O., Hoffmann, G., Cherif, C. (2011). High performance thermoplastic composite from flat knitted multi-layer textile preform using hybrid yarn. Composites Science and Technology, 71(4), 511-519. Abounaim M. Diestel O. Hoffmann G. Cherif C. 2011 High performance thermoplastic composite from flat knitted multi-layer textile preform using hybrid yarn Composites Science and Technology 71 4 511 519 10.1016/j.compscitech.2010.12.029 Search in Google Scholar

Padaki, N. V., Alagirusamy, R., Sugun, B. S. (2006). Knitted preforms for composite applications. Journal of Industrial Textiles, 35(4), 295-321. Padaki N. V. Alagirusamy R. Sugun B. S. 2006 Knitted preforms for composite applications Journal of Industrial Textiles 35 4 295 321 10.1177/1528083706060784 Search in Google Scholar

Abounaim, M., Cherif, C. (2012). Flat-knitted innovative three-dimensional spacer fabrics: a competitive solution for lightweight composite applications. Textile Research Journal, 82(3), 288-298. Abounaim M. Cherif C. 2012 Flat-knitted innovative three-dimensional spacer fabrics: a competitive solution for lightweight composite applications Textile Research Journal 82 3 288 298 10.1177/0040517511426609 Search in Google Scholar

Qi, Y. X., Li, J. L., Liu, L. S. (2014). Tensile properties of multilayer-connected biaxial weft knitted fabric reinforced composites for carbon fibers. Materials and Design, 54(2), 678-685. Qi Y. X. Li J. L. Liu L. S. 2014 Tensile properties of multilayer-connected biaxial weft knitted fabric reinforced composites for carbon fibers Materials and Design 54 2 678 685 10.1016/j.matdes.2013.08.051 Search in Google Scholar

Gao, X. P., Li, D. X., Wu, W., Chen, S. (2016). Experimental investigation of the tensile and bending behavior of multi-axial warp-knitted fabric composites. Textile Research Journal, 88, 333-344. Gao X. P. Li D. X. Wu W. Chen S. 2016 Experimental investigation of the tensile and bending behavior of multi-axial warp-knitted fabric composites Textile Research Journal 88 333 344 10.1177/0040517516679155 Search in Google Scholar

Liu, D. H., Tang, M. J., Yan, J. H. (2021). Comparative study of the tensile properties of 2D and UD overbraided multilayer composites. Composites science and technology, 210, 108,817. Liu D. H. Tang M. J. Yan J. H. 2021 Comparative study of the tensile properties of 2D and UD overbraided multilayer composites Composites science and technology 210 108,817 10.1016/j.compscitech.2021.108817 Search in Google Scholar

Truong, V. D., Kim, D. J. (2021). A review paper on direct tensile behavior and test methods of textile reinforced cementitious composites. Composite Structures, 263, 113,661. Truong V. D. Kim D. J. 2021 A review paper on direct tensile behavior and test methods of textile reinforced cementitious composites Composite Structures 263 113,661 10.1016/j.compstruct.2021.113661 Search in Google Scholar

Tian, Q., Qin, Z. G., Shi, B., Jia, L. X., Lu, S. L., Yan, R. S. (2021). Low - velocity impact resistance and acoustic emission evaluation on mechanical failure of carbon fiber weft - knittin - reinforced composites. Polymers for Advanced Technologies, 32(8), 3,123-3,136. Tian Q. Qin Z. G. Shi B. Jia L. X. Lu S. L. Yan R. S. 2021 Low - velocity impact resistance and acoustic emission evaluation on mechanical failure of carbon fiber weft - knittin - reinforced composites Polymers for Advanced Technologies 32 8 3,123 3,136 10.1002/pat.5325 Search in Google Scholar

Zhou, W., Qin, R., Han, K. N., Wei, Z. Y., Ma, L. H. (2020). Progressive damage visualization and tensile failure analysis of three-dimensional braided composites by acoustic emission and micro-CT - ScienceDirect. Polymer Testing, 93, 106,881. Zhou W. Qin R. Han K. N. Wei Z. Y. Ma L. H. 2020 Progressive damage visualization and tensile failure analysis of three-dimensional braided composites by acoustic emission and micro-CT - ScienceDirect Polymer Testing 93 106,881 10.1016/j.polymertesting.2020.106881 Search in Google Scholar

Njuhovic, E., Braeu, M., Wolff-Fabris, F., Starzynski, K., Altstaedt, V. (2015). Identification of failure mechanisms of metallised glass fibre reinforced composites under tensile loading using acoustic emission analysis. Composites Part B: Engineering, 81, 1-33. Njuhovic E. Braeu M. Wolff-Fabris F. Starzynski K. Altstaedt V. 2015 Identification of failure mechanisms of metallised glass fibre reinforced composites under tensile loading using acoustic emission analysis Composites Part B: Engineering 81 1 33 10.1016/j.compositesb.2015.06.018 Search in Google Scholar

Castellano, A., Fraddosio, A., Piccioni, M. D. (2018). Quantitative analysis of QSI and LVI damage in GFRP unidirectional composite laminates by a new ultrasonic approach. Composites Part B: Engineering, 151(10), 106-117. Castellano A. Fraddosio A. Piccioni M. D. 2018 Quantitative analysis of QSI and LVI damage in GFRP unidirectional composite laminates by a new ultrasonic approach Composites Part B: Engineering 151 10 106 117 10.1016/j.compositesb.2018.06.003 Search in Google Scholar

Caminero, M. A., Garcia-Moreno, I., Rodriguez, G. P., Chacon, J. M. (2019). Internal damage evaluation of composite structures using phased array ultrasonic technique: Impact damage assessment in CFRP and 3D printed reinforced composites. Composites Part B: Engineering, 165, 131-142. Caminero M. A. Garcia-Moreno I. Rodriguez G. P. Chacon J. M. 2019 Internal damage evaluation of composite structures using phased array ultrasonic technique: Impact damage assessment in CFRP and 3D printed reinforced composites Composites Part B: Engineering 165 131 142 10.1016/j.compositesb.2018.11.091 Search in Google Scholar

Marani, R., Palumbo, D., Reno, V., Galietti, U., Stella, E., Dorazio, T. (2018). Modeling and classification of defects in CFRP laminates by thermal non-destructive testing. Composites Part B: Engineering, 135, 129-141. Marani R. Palumbo D. Reno V. Galietti U. Stella E. Dorazio T. 2018 Modeling and classification of defects in CFRP laminates by thermal non-destructive testing Composites Part B: Engineering 135 129 141 10.1016/j.compositesb.2017.10.010 Search in Google Scholar

Harizi, W., Chaki, S., Bourse, G., Ourak, M. (2014). Mechanical damage assessment of polymer–matrix composites using active infrared thermography. Composites Part B: Engineering, 66, 204-209. Harizi W. Chaki S. Bourse G. Ourak M. 2014 Mechanical damage assessment of polymer–matrix composites using active infrared thermography Composites Part B: Engineering 66 204 209 10.1016/j.compositesb.2014.05.017 Search in Google Scholar

Liu, X. D., Zhang, D. T., Sun, J., Yu, S., Qian, K. (2020). Refine reconstruction and verification of meso-scale modeling of three-dimensional five-directional braided composites from X-ray computed tomography data. Composite Structures, 245, 112,347. Liu X. D. Zhang D. T. Sun J. Yu S. Qian K. 2020 Refine reconstruction and verification of meso-scale modeling of three-dimensional five-directional braided composites from X-ray computed tomography data Composite Structures 245 112,347 10.1016/j.compstruct.2020.112347 Search in Google Scholar

Chai, Y., Wang, Y., Yousaf, Z., Vo, N. T., Withers, P. J. (2020). Damage evolution in braided composite tubes under torsion studied by in-situ X-ray computed tomography. Composites Science and Technology, 188, 107,976. Chai Y. Wang Y. Yousaf Z. Vo N. T. Withers P. J. 2020 Damage evolution in braided composite tubes under torsion studied by in-situ X-ray computed tomography Composites Science and Technology 188 107,976 10.1016/j.compscitech.2019.107976 Search in Google Scholar

Monti, A., Mahi, A. E., Jendli, Z., Guillaumat, L. (2016). Mechanical behaviour and damage mechanisms analysis of a flax-fibre reinforced composite by acoustic emission. Composites Part A: Applied Science and Manufacturing, 900, 100-110. Monti A. Mahi A. E. Jendli Z. Guillaumat L. 2016 Mechanical behaviour and damage mechanisms analysis of a flax-fibre reinforced composite by acoustic emission Composites Part A: Applied Science and Manufacturing 900 100 110 10.1016/j.compositesa.2016.07.002 Search in Google Scholar

Jung, D. Y., Mizutani, Y., Todoroki, A., Na, W. (2021). Effect of ultraviolet irradiation on the material properties and acoustic emission of a fiber-reinforced composite. Fibers and Polymers, 22(7), 1,940-1,949. Jung D. Y. Mizutani Y. Todoroki A. Na W. 2021 Effect of ultraviolet irradiation on the material properties and acoustic emission of a fiber-reinforced composite Fibers and Polymers 22 7 1,940 1,949 10.1007/s12221-021-0423-1 Search in Google Scholar

Mohammadi, R., Najafabadi, M. A., Saghafi, H., Saeedifar, M., Zarouchas, D. (2021). A quantitative assessment of the damage mechanisms of CFRP laminates interleaved by PA66 electrospun nanofibers using acoustic emission. Composite Structures, 258, 113,395. Mohammadi R. Najafabadi M. A. Saghafi H. Saeedifar M. Zarouchas D. 2021 A quantitative assessment of the damage mechanisms of CFRP laminates interleaved by PA66 electrospun nanofibers using acoustic emission Composite Structures 258 113,395 10.1016/j.compstruct.2020.113395 Search in Google Scholar

Ma, Q., Wang, K., Wang, S. D., Liu, H., Jin, B. C., Jin, L. M., Ma, Pi. B. (2018). Tensile damage mechanism of 3-D angle-interlock woven composite using acoustic emission events monitoring. Autex Research Journal, 18(1), 46-50. Ma Q. Wang K. Wang S. D. Liu H. Jin B. C. Jin L. M. Ma Pi. B. 2018 Tensile damage mechanism of 3-D angle-interlock woven composite using acoustic emission events monitoring Autex Research Journal 18 1 46 50 10.1515/aut-2017-0010 Search in Google Scholar

Romhany, G., Czigány, T., Karger-Kocsis, J. (2017). Failure assessment and evaluation of damage development and crack growth in polymer composites via localization of acoustic emission events: A review. Polymer Reviews, 57(3), 397-439. Romhany G. Czigány T. Karger-Kocsis J. 2017 Failure assessment and evaluation of damage development and crack growth in polymer composites via localization of acoustic emission events: A review Polymer Reviews 57 3 397 439 10.1080/15583724.2017.1309663 Search in Google Scholar

Saeedifar, M., Zarouchas, D. (2020). Damage characterization of laminated composites using acoustic emission: A review. Composites Part B: Engineering, 195, 108,039. Saeedifar M. Zarouchas D. 2020 Damage characterization of laminated composites using acoustic emission: A review Composites Part B: Engineering 195 108,039 10.1016/j.compositesb.2020.108039 Search in Google Scholar

Xu, G. Y., Zhuang, Y. L., Xia, R., Cheng, J. Y., Zhang, Y. C. (2012). Carbon nanotubes induced nonisothermal crystallization of ultrahigh molecular weight polyethylene with reduced chain entanglements. Materials Letters, 89, 272-275. Xu G. Y. Zhuang Y. L. Xia R. Cheng J. Y. Zhang Y. C. 2012 Carbon nanotubes induced nonisothermal crystallization of ultrahigh molecular weight polyethylene with reduced chain entanglements Materials Letters 89 272 275 10.1016/j.matlet.2012.09.002 Search in Google Scholar

Yan, R. S., Zhang, Q. Y., Shi, B., Liu, S., Jia, L. X. (2020). Investigation on low-velocity impact and interfacial bonding properties of weft-knitted UHMWPE reinforced composites. Journal of Industrial Textiles, https://doi.org/10.1177/1528083720931474. Yan R. S. Zhang Q. Y. Shi B. Liu S. Jia L. X. 2020 Investigation on low-velocity impact and interfacial bonding properties of weft-knitted UHMWPE reinforced composites Journal of Industrial Textiles https://doi.org/10.1177/1528083720931474 10.1177/1528083720931474 Search in Google Scholar

Zhuang, X. M., Yan, X. (2006). Investigation of damage mechanisms in self-reinforced polyethylene composites by acoustic emission. Composites Science and Technology, 66, 444-449. Zhuang X. M. Yan X. 2006 Investigation of damage mechanisms in self-reinforced polyethylene composites by acoustic emission Composites Science and Technology 66 444 449 10.1016/j.compscitech.2005.07.013 Search in Google Scholar

Ogale, V., Alagirusamy, R. (2007). Tensile properties of GF-polyester, GF-nylon, and GF-polypropylene commingled yarns. Journal of the Textile Institute Proceedings and Abstracts, 98(1), 37-45. Ogale V. Alagirusamy R. 2007 Tensile properties of GF-polyester, GF-nylon, and GF-polypropylene commingled yarns Journal of the Textile Institute Proceedings and Abstracts 98 1 37 45 10.1533/joti.2005.0181 Search in Google Scholar

Zhou, W., Shang, Y. J., Zhang, P. F., Yin, H. F., Ma, L. H. (2020). Statistical analysis of acoustic emission signals and tensile deformation measurement for three dimensional carbon fiber braided composites. SN Applied Sciences, 2(7), 1,237. Zhou W. Shang Y. J. Zhang P. F. Yin H. F. Ma L. H. 2020 Statistical analysis of acoustic emission signals and tensile deformation measurement for three dimensional carbon fiber braided composites SN Applied Sciences 2 7 1,237 10.1007/s42452-020-3069-5 Search in Google Scholar

Li, L., Lomov, S. V., Yan, X. Carvelli, V. (2014). Cluster analysis of acoustic emission signals for 2D and 3D woven glass/epoxy composites. Composite Structures, 116(1), 286-299. Li L. Lomov S. V. Yan X. Carvelli, V. 2014 Cluster analysis of acoustic emission signals for 2D and 3D woven glass/epoxy composites Composite Structures 116 1 286 299 10.1016/j.compstruct.2014.05.023 Search in Google Scholar

Saeedifar, M., Najafabadi, M. A., Zarouchas, D., Toudeshky, H. H., Jalalvand, M. (2018). Clustering of interlaminar and intralaminar damages in laminated composites under indentation loading using acoustic emission. Composites Part B: Engineering, 144, 206-219. Saeedifar M. Najafabadi M. A. Zarouchas D. Toudeshky H. H. Jalalvand M. 2018 Clustering of interlaminar and intralaminar damages in laminated composites under indentation loading using acoustic emission Composites Part B: Engineering 144 206 219 10.1016/j.compositesb.2018.02.028 Search in Google Scholar

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