Effects of fabric architectures on mechanical and damage behaviors in carbon/epoxy woven composites under multiaxial stress states

The mechanical properties and damage evolutions of carbon/epoxy woven fabric composites with three different fabric architectures, including one plain weave and two twill weave patterns, are experimentally investigated under multiaxial stress states. In particular, the effects of weave patterns are investigated by monotonic and cyclic off-axis tension tests. Both elastic modulus and strength degrade remarkably with increasing off-axis loading angle, while Poisson's ratio is much higher than that measured from on-axis tests and increases with loading strain gradually. Different fabric architectures show limited effects on the modulus and strength under multiaxial stress states, and they are well predicted by transformation equation and Tsai-Wu failure criteria, respectively. However, significantly different failure behaviors are observed in three fabric composites, and microstructure observation shows that fabric architecture affects the stress concentration and the damage development. Smaller crimp ratio and compacted structure postpone the damage development but result in more abrupt failure under multiaxial stress states.     

Influence of fabric geometry on yarn pull‐out property and wear performance of hybrid S‐glass/PTFE fabric‐reinforced composites

The friction states between yarns affect the stress transferred in fabric and the fabric structure significantly affects the tribological properties of composites. In this aricle, the effects of fabric structure on yarn pull‐out property and tribological performance of composite were thoroughly studied. Four different fabrics with same tissue cycles number and thread count (2/2 double twills, 1/3 twill, 4‐shaft satin, and 4‐shaft reinforced satin) were used to evaluate the yarn pull‐out property in fabric and the tribological performance of corresponding composites. The results indicate that fabric structure has a significant effect on the yarn pull‐out property in fabric. In particular, the yarn pull‐out property of 4‐shaft reinforced satin was best in the four fabrics structure used in this article owing to the excellent integrity of the 4‐shaft reinforced satin fabric structure and the distribution characteristics of the fabric intersection points. The tribological performance of the 4‐shaft reinforced satin fabric enhanced composites were positively correlated with yarn pull‐out property because the yarn pull‐out property in fabric played an important role in energy dissipation and load carry capacity.     

High strain rate out-of-plane compression properties of aramid fabric reinforced polyamide composite

The composite-structure protective systems in head-on collision with objects are largely subjected to dynamic compression load along the thickness of composite structure. A typical plain weave aramid fabric reinforced polyamide (PA) composite, which is defined as one of single polymer composites (SPCs), is addressed in this paper. Firstly, in the process of sample preparation, processing characteristics of the single polymer composites are skillfully achieved and discussed using differential scanning calorimetry (DSC) and capillary rheometer. Secondly, the out-of-plane compression properties of the composite are studied on Split Hopkinson Pressure Bar (SHPB) apparatus in the strain rate range of 400–1200s⁻¹. Effects of fiber content and strain rate on dynamic off-plane compression properties are investigated and quasi-static properties are obtained on a universal testing machine as a comparison. Results provide a basis for selecting composite composition and lay-up for designing armor with improved impact resistance. Additionally, penetration of the resin through the fabric is observed by the digital microscope and the internal damage of the laminates is qualitatively predicted by the microstructure of the internal fabric yarns.     

Stress wave attenuation in composites during ballistic impact

Experimental studies are presented on stress wave attenuation during ballistic impact for four types of polymer matrix composites. The materials considered are plain weave E-glass/epoxy, 8H satin weave T300 carbon/epoxy and two types of hybrid composite made using plain weave E-glass fabric and 8H satin weave T300 carbon fabric with epoxy resin. Strain profiles were obtained during ballistic impact event at certain distances from the point of impact. There is stress wave attenuation leading to reduction in peak strains obtained as the stress wave propagates away from the point of impact. Further, it is observed that ballistic limit velocity, V₅₀, can be increased compared to carbon only composites by adding E-glass layers to T300 carbon layers.     

Low velocity impact response of flax/polypropylene hybrid roving based woven fabric composites: Where does it stand with respect to GRPC?

Flax-PP based thermally bonded roving (TBR) has a unique structure where the flax fibres remain twist-free and fully aligned along the roving axis. The present study describes an experimental investigation on the low velocity impact (LVI) behaviour of the TBR based woven fabric composites and compares the same with plain woven glass fabric reinforced PP composites (GRPC). Two different fabric architectures namely plain woven (PW) and unidirectional (UD) are fabricated using flax/PP based TBR. These TBR based woven fabrics and the glass fabric/PP sheets are consolidated in a compression moulding machine and the resultant composite-laminates are tested for their LVI behaviour. The impact test results revealed that the glass/PP composites absorb more energy and exhibit a higher peak load than both TBR based PW and UD fabric composites. However, the specific load and energy of all flax/PP composites are higher than the glass/PP composite. The damage tolerance of all composite laminates are evaluated by comparing their flexural strength before and after the impact. It is observed that the proportionate loss in flexural strength due to impact thrust is larger in case of glass/PP composites than all flax-PP composites.     

Structural design and impact resistance of three-dimensional structure-reinforced flexible polymer composites

Three-dimensional (3D) structure-reinforced flexible polymer composites have great potential as personal protective materials. These composites exhibit excellent mechanical properties and failure mechanisms than typical rigid composites because of the complex dynamic reaction processes caused by the 3D structure in response to impact. This paper comprehensively reviews the impact resistance mechanism of 3D structure-reinforced flexible polymer composites by combining current results with relevant investigations. 3D woven fabric reinforcements and flexible matrix materials of flexible polymer composites systems are presented in this paper. The classification for 3D woven fabric reinforcements is reviewed, as well as the effect of reinforcement structures on the impact resistance of the flexible composites. Furthermore, several flexible matrix are introduced. Several external factors affecting the impact resistance of composites are then discussed. Finally, the impact damage mechanism of 3D structure-reinforced flexible polymer composites is summarized and analyzed.     

Vibration isolation behaviour of 3D polymeric knitted spacer fabrics under harmonic vibration testing conditions

The use of 3D knitted spacer fabrics made of polymeric fibre materials as vibration isolators is proposed in this study by considering their spacer monofilaments as Euler springs which have been proved to be excellent vibration isolators. Three types of spacer fabrics with different compression force–displacement characteristics were fabricated by varying monofilament diameter and fabric thickness. Their vibration transmissibility under harmonic vibration testing conditions was measured by an electromagnetic shaker. It is found that the resonant frequency and isolation frequency of these fabrics decrease with increasing acceleration level and load mass, and a thicker fabric has better vibration isolation performance due to its lower resonant and isolation frequencies. The study shows that 3D knitted spacer fabrics can be designed as good human vibration isolators without compromising their comfort.     

Multiscale carbon nanotube-carbon fiber reinforcement for advanced epoxy composites

We report an approach to the development of advanced structural composites based on engineered multiscale carbon nanotube-carbon fiber reinforcement. Electrophoresis was utilized for the selective deposition of multi- and single-walled carbon nanotubes (CNTs) on woven carbon fabric. The CNT-coated carbon fabric panels were subsequently infiltrated with epoxy resin using vacuum-assisted resin transfer molding (VARTM) to fabricate multiscale hybrid composites in which the nanotubes were completely integrated into the fiber bundles and reinforced the matrix-rich regions. The carbon nanotube/carbon fabric/epoxy composites showed approximately 30% enhancement of the interlaminar shear strength as compared to that of carbon fiber/epoxy composites without carbon nanotubes and demonstrate significantly improved out-of-plane electrical conductivity.     

碳纤维三向织物/环氧树脂复合材料的制备与力学性能

选择不同纱线间距[即二经(纬)纱之间的中心距]尺寸的碳纤维三向织物,采用热压成型技术制备了碳纤维三向织物/环氧树脂复合材料.研究了纱线间距及样品裁剪角度等对力学性能的影响,并与碳纤维二向织物/环氧树脂复合材料的力学性能进行对比.结果表明,随着纱线间距尺寸从2 mm增加到6 mm,0°方向断裂强度从221. 7 MPa下降到148. 1 MPa,撕裂强力从1000 N下降到600 N; 90°方向断裂强度从50. 0MPa下降到22. 1 MPa,撕裂强力从330 N下降到100 N;顶破强力从424 N下降到216 N.这些力学性能的逐渐降低是单位面积的碳纤维增强体含量减少和织物的孔洞增大共同作用的结果.纱线间距为2 mm的碳纤维三向织物复合材料在0°(以纬纱为基准),30°,45°,60°和90°方向的断裂强度分别为221. 7,48. 5,44. 3,227. 7和50. 0 MPa,即断裂强度在0°和60°方向大于在30°,45°及90°方向.由三向织物的编织原理可知,0°与60°方向完全相同,因此其断裂强度相似,且样品中有一组纱线与外加载荷平行,对形变破坏具有一定的约束作用,而...     

Self‐reinforced polypropylene composites based on low‐cost commercial woven and non‐woven fabrics

In the present paper, different self‐reinforced polypropylene (PP) composites based on low‐cost commercial woven (w) and non‐woven (nw) fabrics were obtained. Hot compaction (HC) and film stacking (FS) followed by compression molding were used to prepared the composites. The fracture and failure behavior of the different materials was determined under different testing conditions through quasi‐static uniaxial tensile tests, Izod impact experiments and by means of fracture mechanics tests on mode I double‐edge deeply notched tensile specimens. In the case of the composite obtained by film stacking + compression molding (rPP/nw/w‐FS) and the hot‐compacted composite (nw/w‐HC) containing simultaneously woven and non‐woven fabrics, the acoustic emission technique was applied in situ in the tensile tests to determine their consolidation quality and to identify the failure mechanisms responsible for their fracture behavior. It was observed that both composites exhibited relatively similar high consolidation quality. However, the hot‐compacted composite presented a more uniform distribution of failure mechanisms (debonding and fiber fracture) than the film‐stacked composite. The hot‐compacted composite containing both types of reinforcements exhibited the best combination of mechanical (tensile, impact, and fracture) properties. Therefore, this composite appeared as the most promising for structural applications among the different composites investigated.     

A study of the thermal properties of bamboo knitted fabrics

In this research, the thermal properties of bamboo single jersey knitted fabrics have been studied in relation to stitch length and yarn linear density in tex. The objective was to determine the influence of fabric factors like stitch length and the constituent yarn linear density on fabric properties, such as air permeability, thermal conductivity, thermal resistance and relative water vapour permeability. Yarns with linear densities of 19.6, 23.6, 29.5 tex and with the same twist level were used to construct the fabrics of single jersey structure with stitch lengths of 0.27, 0.29 and 0.31 cm. The anticipated increase in air permeability and relative water vapour permeability with decrease in yarn linear density and increase in stitch length was observed. The thermal conductivity and thermal resistance tended in general to increase with constituent yarn linear density but decreased with increase in stitch length.     

Experimental investigation on mechanical properties of unidirectional and woven fabric glass/epoxy composites under off-axis tensile loading

Mechanical properties of unidirectional (UD) and woven fabric glass/epoxy composites under off-axis tensile loading were experimentally investigated. A number of off-axis tests considering different fibre orientations were performed to study the character and failure mechanisms of the composite laminates. The experimental results indicated that both off-axis elastic moduli and strength degrade with increasing off-axis angle in all cases, and the woven fabric composites present nonlinear stress-strain behaviour under off-axial tension loading. The Tsai-Wu criteria used for failure analysis of the UD and woven fabric composites were compared and discussed, especially considering different values of interaction coefficient F₁₂. The prediction results demonstrated that the Tsai-Wu criterion can be used successfully to analyse failure properties of the woven fabric composites under multiaxial stress conditions, where the criterion with the modified coefficient F₁₂ obtained from the 45° off-axial tension tests is better and has higher accuracy. Finally, the specific failure modes were compared in the UD and woven fabric composites. The selected fracture surfaces were also observed by scanning electron microscopy (SEM), and the corresponding failure mechanisms of the woven fabric composites under off-axis tensile loading were identified.     

Effect of wood sawdust filler on the mechanical properties of Indian mallow fiber yarn mat reinforced with polyester composites

The research article focused on the effect of wood sawdust as secondary filler reinforcement in Indian mallow fiber yarn mat reinforced with polyester composites. Composites were fabricated along the transverse and longitudinal orientation in six different combinations by compression molding machine. The mechanical properties of composites by single and double layer yarn mat with and without wood sawdust filler were evaluated while loading composites specimen on warp and weft direction at the first time in this research paper. The Indian mallow fiber double layer longitudinal orientation yarn mat/wood sawdust filler/polyester composite specimen along the warp direction was found to exhibit optimum mechanical properties compared to other composites. Furthermore, the Indian mallow fiber yarn mat composites were fabricated with helmet and civil construction pipes at first time in this work to replace the synthetic fiber through natural fiber. Scanning electron microscopy was performed to study the morphologies of internal crack and fractured surface of composites.     

Mechanical,low-velocity impact,and hydrothermal aging properties of flax/carbon hybrid composite plates

A hybrid of flax and carbon fibers was considered as an effective way to enhance the mechanical and hydrothermal resistance of flax-reinforced polymer composites. In this study, hybrid composites based on three layers of cross-ply flax fabrics, two layers of unidirectional carbon fabrics, and an epoxy resin were investigated in terms of the tensile, three-point bending, impact, and water absorption properties. The flax fabric reinforcement of the hybrid composites contributed to an improvement in the toughness, whereas the carbon fabric contributed to an improvement in their hydrothermal resistance and overall strength and stiffness. The hybrid composites with carbon fibers on the surface (CFFFC) exhibited brittle failure in the tensile test, whereas those with alternating layers (FCFCF) exhibited greater plastic deformation. In addition, the failure strain of the CFFFC samples showed a negative hybrid effect, whereas that of the FCFCF samples improved 63.5% compared with that of carbon-fiber-reinforced polymer composites. A positive hybrid effect on the impact performance of hybrid reinforced epoxy composites containing the unidirectional carbon fabric and cross-ply flax fabric was observed. At 40 °C and 80% relative humidity, the diffusion rate of water molecules in the FCFCF samples was 16 times that in the CFFFC samples.     

Fabrication and Mechanical Performance of Non-Crimp Unidirectional Jute-Yarn Preform-Based Composites

This work developed novel jute-yarn, non-crimp, unidirectional (UD) preforms and their composites, with three different types of warp jute yarns of varying linear densities and twists in the dry UD preforms, in order to present a possible solution to the detrimental effects of higher yarn twists and crimp at the warp–weft yarn interlacements of traditional, woven, preform-based composites on their mechanical properties. In the developed UD preforms, warp jute yarns were placed in parallel by using a wooden picture-frame pin board, with the minimal number of glass weft yarns to avoid crimp at the warp–weft yarns interlacements, which can significantly enhance the load-bearing ability of UD composites compared to traditional, woven, preform composites. It was found that an optimal combination of jute warp yarn linear densities and twists in the UD preforms is important to achieve the best possible mechanical properties of newly developed UD composites, because it encourages a proper polymer-matrix impregnation on jute fibres, leading to excellent fibre–matrix interface bonding. Composites made from the 25 lb/spindle jute warp yarn linear density (UD25) exhibited higher tensile and flexural properties than other UD composites (UD20, UD30). All the UD composites showed a much better performance compared to the traditional woven preform composites (W20), which were obviously related to the higher crimp and yarn interlacements, less load-carrying capacity, and poor fiber–matrix interfaces of W20 composites. UD25 composites exhibited a significant enhancement in tensile modulus by ~232% and strength by ~146%; flexural modulus by 138.5% and strength by 145% compared to W20 composites. This reveals that newly developed, non-crimp, UD preform composites can effectively replace the traditional woven composites in lightweight, load-bearing, complex-shaped composite applications, and hence, this warrants further investigations of the developed composites, especially on long-term and dynamic-loading mechanical characterizations.     

Impact behaviour of Dyneema® fabric-reinforced composites with different resin matrices

This paper presents an experimental study on the impact behaviour of composite laminates made of a Dyneema^® woven fabric and four different resin matrices. Three thicknesses of each kind of resin laminate were subjected to impact by a spherical steel projectile in a velocity regime ranging from 100 to 200 m/s. The results revealed that the laminates having flexible matrices performed much better in perforation resistance and energy absorption, but had a greater extent of deformation and damage than the counterparts with rigid matrices. It was found that the matrix rigidity played a crucial role in controlling the propagation of transverse deformation, and thereby the local strain and perforation resistance of laminates. The more rigid matrix restrained the laminate's transverse deformation to a smaller area at a given time, which led to higher local strain and lower perforation resistance. Fibre failure in tension was identified as the dominant failure mechanism for the tested laminates.     

Preparation of SiO2@polystyrene@polypyrrole sandwich composites and hollow polypyrrole capsules with movable SiO2 spheres inside

In this paper, we describe a flexible method for preparing conducting building blocks: SiO2@polystyrene@polypyrrole sandwich multilayer composites and hollow polypyrrole (PPy) capsules with movable SiO2 spheres inside. First, SiO2@polystyrene (PS) core/shell composites were synthesized, and then SiO2@PS@PPy sandwich multilayer composites were prepared by chemical polymerization of pyrrole monomer on the surface of SiO2@PS composites. Furthermore, hollow polypyrrole capsules with movable SiO2 spheres inside were obtained after removal of the middle PS layer. The diameter of sandwich multilayer composites could easily be controlled by adjusting the dosage of pyrrole monomer. The conductivities of composites increased with the increase of PPy content. After the insulating PS layer was selectively etched, the conductivities of hollow capsules with movable SiO2 spheres inside were much higher than those of the corresponding sandwich multilayer composites.     

Compression-moulded flax fabric-reinforced polyfurfuryl alcohol bio-composites

Bio-composites (FF-PFA-D) were successfully compression moulded by reinforcing polyfurfuryl alcohol (PFA) with 10 layers of woven flax fabric (FF). FF-reinforced PFA-based bio-composites were then immersed in water to get wet bio-composite samples (FF-PFA-W). Mechanical and impact properties of the bio-composites in dry and wet state were determined. Characterisations of the bio-composites were performed by thermogravimetric analysis, thermomechanical behaviour, and cone calorimeter data. Results indicated the increase in α-relaxation temperature for FF-PFA-W. SEM micrograph showed that the flax fibres were completely coated with the resin indicating complete wetting of the fabrics by the matrix. As expected, time of ignition showed an increase for the bio-composites due to the flame retardant characteristics of PFA. This work gives us simple and effective way to prepare bio-composites from 100 % renewable resources.     

Effect of internal mold release agent on flexural and inter laminar shear properties of carbon and glass fabric reinforced thermoset composites

The study is focused on thermoset composites reinforced with carbon and glass woven fabrics. Two types of thermoset resins, for example, epoxy and vinyl ester were used as the matrix. Varying concentrations of internal mold releasing (IMR) agent was used in the resin. The composites were cured both at room temperature and at 80°C. The flexural properties were studied using 3‐point bending test method. Further theinter‐laminar shear strength (ILSS) was investigated using the short beam shear strength test based on 3‐point bending. The flexural modulus of room temperature cured epoxy resin is higher than that of high temperature cured epoxy resin and cured vinyl ester resin. The flexural modulus is lowest for 1% IMR sample in epoxy system and the modulus for 0% and 2% epoxy are not significantly different. Lowest flexural strength and modulus can be observed for the combination of reinforcement and curing conditions for samples containing 1% IMR for the epoxy systems. Carbon fiber is found to be less compatible with the vinyl ester resin system and the addition of IMR to the resin degraded the properties further. Inter‐laminar shear strength for epoxy‐based composites is not much affected by presence of IMR, but in case of vinyl ester based composites there is a decrease in ILSS on addition of IMR agent. The study explains variation in flexural properties on addition of IMR and change of curing conditions. These results can be used for ascertaining variation in mechanical properties in real use.     

电子束作用下双酚A型环氧树脂体系的固化特征

当前 ,先进树脂基复合材料基本上都是采用加热固化成型的 ,由于其工艺周期长 ,造成复合材料的制造成本较高 ,同时 ,热固化采用的固化剂和有机溶剂往往会对操作人员及环境造成危害 .为顺应复合材料低成本化和无公害化的发展趋势 ,树脂基复合材料的电子束辐射固化技术逐渐发展起来 .复合材料的电子束固化技术是在 2 0世纪 80年代初 ,由法国Ａｅｒｏｐａｔｉｃｌｅ的研究人员首先进行的[1] .近年来 ,美国、日本、加拿大及欧洲的许多国家都在积极从事于研究和利用此项技术 ,并且已经取得了可观的成果[2 ] .我国在这方面的研究工作也开始起步 .作…