Properties Of High Performance Fiber Research Articles

Effect of aramid nanofibers on interfacial properties of high performance fiber reinforced composites

ABSTRACT High performance fiber reinforced composites (HPFRC) have attracted considerable attention due to their high strength, high modulus and good designability. But the poor interface due to the smooth fiber surface and few active groups limits the application of the composites. Aramid nanofibers (ANFs) have been widely used as polymer framework in electrical and biological fields due to its large specific surface area and high mechanical properties. In this work, robust HPFRC was achieved via dip-coating approach of the fabrics. Instead of Kevlar fiber, Poly(p-phthaloyl-p-phenylenediamine) (PPTA) were served as precursor to prepare ANF solution. Aramid and carbon fabrics were then impregnated with ANF solution to study the effect of ANF on the interfacial properties of fiber reinforced composites. After modification, the roughness and polarity of the fiber were considerably improved. The inter-laminar shear strength (ILSS), mode I fracture toughness, GIC, and flexural properties of the composites were greatly enhanced, indicating that the study provides an effective method to achieve high strength HPFRC.

Investigation on the Influence of Type of Steel Fibers on Shear Failure of HPFRCC Beams

This paper investigates the influence of different types of steel fiber on the mechanical properties of High Performance Fiber Reinforced Cementitious Composite (HPFRCC) as well as the shear failure mode of steel reinforced HPFRCC beams. Moreover, the influence of parameters such as span to effective depths (a/d) ratio of beams and longitudinal reinforcement ratio on shear strength of HPFRCC beams are examined. In reference to the results, despite the same tensile strength of both straight and hooked fibers utilized, the performance of straight steel fiber is superior to the hooked steel fiber due to its physiognomies. However, the beam specimens with straight steel fiber exhibit considerably lower deflection and ultimate load capacity when subjected to shear load. Also, the results show that the influence of type of steel fiber is more significant than the influence of longitudinal reinforcement ratio, i.e. the beam specimen with hooked steel fiber and 0.94% reinforcement ratio displayed higher deflection and ultimate shear load capacity compared to the specimen with straight steel fiber and 1.88% longitudinal reinforcement ratio.

Effect of Tropical Climate Condition to Compressive Strength and Microstructure Properties of High Performance Fiber Reinforced Reinforced Concrete (HPFRC)

Additional of fiber in concrete creates fiber reinforced concrete (FRC) with an improvement of the mechanical properties of the concrete. However, fiber incorporation in FRC is limited to 2% to allow normal mixing procedure. To address this issue, high performance fiber reinforced concrete (HPFRC) is introduced and it is relatively new in construction industry. Since very limited information on its capacity in tropical climate condition exposure, this research focuses on investigation of compressive strength and microstructure properties of the produced concrete in tropical climate condition. In order to complete this research, grade 80 cement slurry is used with 3%, 4% and 5% hooked-end steel fiber. Total numbers of 56 samples which are divided into 4 sets and exposed to two different curing methods namely water curing method and steam curing method at 80°C. Out of the 4 sets, 2 sets are exposed to tropical climate condition using climatic chamber at 80% relative humidity (RH) and constant temperature of 35°C for 30 days. Compression and ultrasonic pulse velocity (UPV) tests are carried out at 28 days to identify its strength as well as integrity of the concrete produced. Scanning electron microscopy (SEM) analysis is done to ascertain the microstructure properties of HPFRC. The highest compressive strength of 152.2 MPa was recorded for steam curing samples after exposed to tropical climate condition for 30 days with 5% steel fiber volume.

Mechanical properties of high performance fiber reinforced cementitious composites

Extensive experimental studies on High Performance Fiber Reinforced Cement Composites (HPFRCC) owing to their remarkable properties have been carried out. Statistical studies have been mainly focused on Fiber Reinforced Concrete (FRC). An extensive study, including an experimental/statistical approach addressing key mechanical properties (compressive and flexural strength) and impact resistance of such high performance composites with inclusion of different volume of fibers has been carried out on two-hundred and forty specimens in this research.Results from this study revealed that compressive and flexural strength as well as impact resistance of HPFRCC follow the normal distribution. Furthermore, statistical data analyses (both parametric and nonparametric) showed higher percentage of fibers led in greater values for mechanical properties and impact resistance of HPFRCC. Moreover, based on acquired test results, equations were developed between mechanical properties and impact resistance of HPFRCC materials.

Mechanical Properties of High Performance Fiber Reinforced Concrete

Mechanical Properties of High Performance Fiber Reinforced Concrete

Measurement and Research of the Transverse Mechanical Properties of High Performance Fibers

Transverse compression stress-strain curves of a single fiber having a diameter about 10 μm must be measured to obtain transverse compression mechanical properties of high performance fibers. RJY-1 thermo-mechanical analysis instrument that the smallest division value is 0.1 μm can measure the curves of the fibers by installing some auxiliary device on the instrument. The conclu- sion obtained from the features of the curve is that the Kevlar fiber showed a yielding in transverse compression, while Carbon, Ceramic and Glass fibers did not appear the yielding, and their com- pression curves were almost straight up to the point of brittleness. Transverse compression modulus, yield and breaking stress of Kevlar, Carbon and Glass fiber can be obtained from the curves.

Mechanical Properties of Steel Fiber Reinforced Silica Fume Concrete

This paper presents the investigations towards developing a better understanding on the contribution of steel fibers on the compressive, flexural, and splitting tensile strengths of steel fiber reinforced silica fume concrete. An extensive experimentation was carried out with w/cm ratio ranging from 0.25 to 0.40, and fiber content ranging from zero to1.5 percent with an aspect ratio of 80 and silica fume replacement at 5% and 10%. The influence of fiber content in terms of fiber reinforcing index on the mechanical properties of high performance fiber reinforced concrete (HPFRC) with compressive, flexural, and splitting tensile strengths ranging from 55 to 86 MPa, 5.5 to 11 MPa, and 4 to 8.5 MPa respectively is presented. Based on the test results, equations are proposed using statistical methods to predict 28-day strength of HPFRC in terms of fiber reinforcing index for a wide range of w/cm ratios. Relationship between flexural and splitting tensile strengths has been developed using regression analysis. To examine the validity of the proposed model, the experimental results were compared with the values predicted by the model and by the equations of previous researchers, and the absolute variation obtained was within1.50 percent. Addition of 1.5 % volume fraction of crimped steel fiber resulted in 11 % increase in the compressive strength while modulus of rupture and splitting tensile strength increased by 38 % and 56 % respectively.

Microstructure variability and macroscopic composite properties of high performance fiber reinforced cementitious composites

High performance fiber reinforced cementitious composites have made major advances in recent years, to the point where they are being adopted in building and bridge constructions. The most significant advantage of HPFRCC over conventional concrete is their high tensile ductility. However, the tensile strain capacity has been observed to vary, most likely as a result of the variability of the microstructure derived from the processing of these materials. This paper describes the composite property variability, as well as the variability of the material microstructure. Scale linkage is discussed. In particular, the tensile stress–strain curves, and the crack pattern on uniaxially loaded specimens are presented. The treatment of random fibers in micromechanical models, and tailoring of matrix flaw size distribution for saturated multiple cracking are examined. It is suggested that robust composite properties can be achieved by deliberate control of microstructure variability. Some open issues concerning the randomness of microstructures and possibly related macroscopic behavior are also identified. Further gains in composite property control may be expected from improvements in characterization and modeling of the microstructure randomness.

Temperature dependent torsional properties of high performance fibres and their relevance to compressive strength

A simple arrangement for the measurement of torsional moduli of high performance fibres as a function of temperature has been reported. Torsional moduli and damping factors have been measured on a number of polymeric [Kevlar™, poly(p-phenylene benzobisoxazole) (PBO), poly(p-phenylene benzobisthiazole) (PBZT) and Vectran™] and carbon fibres [pitch and PAN based, and one bromine intercalated pitch based carbon fibre] as a function of temperature (room temperature to 150 °C, range) and as a function of vacuum level (1.1–80 ×103 Pa). At these vacuum levels damping in the fine fibres is mainly due to aerodynamic effects. In general PAN based carbon fibres have higher torsional moduli than pitch based carbon fibres. Kelvar™ 149, PBO and PBZT fibres have comparable room temperature torsional moduli, while the torsional modulus of Vectran™ fibre is very low, probably due to the torsional flexibility of the -COO- group. In the above temperature range, torsional moduli of both pitch and PAN based carbon fibres do not change significantly, while for polymeric fibres they decrease; a small decrease is observed for PBO and PBZT, and a significantly higher decrease is observed for Vectran™. Relationships between compressive strength and torsional moduli have been discussed

Interfacial Debonding and Sliding in Brittle Cementmatrix Composites from Steel Fiber Pullout Tests

AbstractA specially designed single fiber pullout apparatus was used to provide simultaneous results on total fiber displacement versus load in addition to monitoring the fiber displacement at the free end. In this apparatus the fiber was going through the entire specimen, which made it possible to determine the point of complete debonding. To control the embedment length a plastic tube was inserted around the fiber. The described fiber pullout test method coupled with an appropriate analysis provides a quantitative determination of interfacial properties which are relevant to toughening of brittle materials through fiber-reinforcement. The technique was used on a high strength cement-based matrix called the Densified Small Particle system (DSP), and on an ordinary strength matrix. Other parameters investigated included fiber embedment length and fiber volume fraction in the cement matrix. The results indicate that: (1) the dense DSP matrix has significantly improved interfacial properties as compared to the ordinary strength matrix; (2) the major energy of pullout in both systems is due to sliding; and (3) both the debonding energy and sliding energy increase with fiber embedment length. These results are important in the understanding of the role of steel fibers in improving the tensile properties of high performance fiber reinforced composites.