Papers by Keyword: Fiber-Reinforced Composites

Abstract: Fiber-reinforced composites are widely used in lightweight design for their exceptional specific strength. However, their inherent multiscale property variations require systematic consideration during structural optimization. This study develops a cross-scale analysis framework and fatigue life prediction model that explicitly accounts for the propagation of mechanical property variations from microscale constituent properties to macroscopic performance, utilizing representative volume element (RVE) modeling. Application of the framework to a carbon fiber composite battery box verifies its predictive capability, with results quantitatively revealing the mechanisms by which property variations affect structural durability. These findings establish a fundamental methodology for evaluating the operational performance of automotive composite structures.

Abstract: Filled polymers seem very promising materials for production. Polymers can be filled with a variety of diverse materials, be it polycaprolactam fiber, glass fiber, or steel wire. Compared to their non-filled counterparts, filled composites have a number of advantages. Production of filled polymers can be challenging due to the processing equipment (the rubber mixer, rollers, and extruders) mixing the fiber with the polymer matrix. In their purest form, polymers mostly don’t have the desired properties, which is why special additives (fillers, plasticizers, dyes, stabilizers, etc.) must be added to obtain the desired functional properties. This is why composites account for an ever greater share of polymers.

Abstract: In tropical regions such as the Philippines, pineapple leaf fiber (PALF) is abundantly available as a low-cost and renewable source for industrial purposes. In this research, PALF was used as a reinforcing material for cement-based composites to open up further possibilities in waste management. Since natural fibers are not fully compatible with the matrix due to their hydrophilic nature, surface treatment is necessary to enhance the fiber-matrix bonding. Fibers were treated using sodium hydroxide (NaOH) with varying concentrations (4%, 8% and 12%) for 6-hr immersion time at room temperature. PALF was then added at varying content (1%, 4% and 7% w/w cement) to the concrete mixture with a design mix ratio of 2:1 (sand: cement) and a constant water-cement ratio of 0.55. The samples were mechanically characterized after 28 curing days following ASTM C209 and ASTM C473. Full factorial experimental design (FFED) was used to investigate the effects of alkali treatment and the fiber content on the mechanical strengths of the composite. Experimental methods, analysis of variance (ANOVA) and normality test were carried out to evaluate, analyze and validate the results. The best results for tensile strength parallel to the surface and flexural strength at 2.028 MPa and 1.495 kN, respectively, were observed at composites with 1% PALF with 4% NaOH. Meanwhile, composites with 1% PALF with 12% NaOH showed the best result for tensile strength perpendicular to the surface at 1.681 MPa. According to ANOVA results, only the model for the tensile strength perpendicular to the surface showed a curvilinear behavior (p-value=0.012). Results revealed that the factor with the most significant effect was the interaction of the fiber content and alkali treatment on the tensile strength parallel to the surface (p-value=0.000), tensile strength perpendicular to the surface (p-value=0.001) and flexural strength (p-value=0.001).

Abstract: There is evidence that the fiber-matrix interaction in fiber-reinforced cementitious composites is determined by the wettability and roughness of the fibers. Due to the high ionic strength in the hydrated cement, also the surface charge or acid/base behavior of the fibers is assumed to play a role. To create fibers with alkaline and acidic surface functionalities, water-insoluble poly (vinyl alcohol) fibers were permanently modified by adsorption of various polyelectrolytes. X-ray photoelectron spectroscopy, zeta potential, and contact angle measurements revealed acidic, alkaline or amphoteric fiber surfaces with advancing water contact angles between 34° and 58°. In a first step to study the interaction with cementitious materials, the interaction of these fibers with pore solution (the liquid phase of hydrated cement) and the adsorption of calcium ions on the fiber surface were investigated. The work will be continued by studying the fiber-matrix interaction in cementitious matrices and its influence on the composite strength.

Abstract: Fiber-reinforced composites have many advantages for many different fields. As for sport teaching, it is also closely connected with fiber-reinforced composites. The paper studies the advantages of fiber-reinforced composites as well as applied equipments to be used in sport teaching. Traditional mode of sports education emphasizes that PE teachers train learners to learn a skill and guide them how to win the game. Rarely do they involve how to guide them to make full use of different tools of different materials to achieve their goals. However, with the advance of information technology, college learners have more freedom to make their choices, which makes sports education in universities and colleges more challenging. This essay is to study the function and effects of applied equipment in sport teaching based on fiber-reinforced composites.

Abstract: The wide range of applications of fiber-reinforced composites in numbers of engineering fields is demanding better understanding on its hydrothermal properties. Especially for those are applied under complex hydrothermal environment such as aircraft industry. However, most methods we used at the present are either complicated or demand high-cost. In this paper, a novel approach based on finite element method (FEM) is proposed to calculate the hydrothermal factor by supposing an original decrease in the laminates stiffness. The integrated strains, consisting of Room Temperature Dry (RTD) strain and FEM simulated strain with the Elevated Temperature Wet (ETW) strain, are used to make an estimate for the hydrothermal factor. Hence, this FEM approach with low cost can be used to calculate the hydrothermal factor without doing full-scale structural ETW experiments. Compared with experimental results of the notched compression and single-bolted joints, it can be concluded that the approach introduced in the present paper can predict excellently the determination scope of the hydrothermal factor reasonably even in structural scale.

Abstract: In this paper, an attempt is made to introduce the defect types relevant to ultrasonic non-destructive testing, and then, we explain how these defects generate in fiber-reinforced composites. The common failure modes which occur are described and discussed. The significance of each of the fracture mechanisms, in terms of their effects on the residual load-bearing properties, is considered. The second part describes briefly the main relevant ultrasonic NDT methods used to identify these defects and indicates the sensitivity to the different types of defect.

Abstract: For analyzing the effects of specimen-dimension on dynamic behaviors of fiber-reinforced composites, 4 kinds of CFRP specimens for different dimension were designed and made. The compressive loading tests were conducted by Ф 37mm split Hopkinson pressure bar (SHPB) system. The results show that the dynamic compression effects of specimen-dimension were exposed. An amount of Fiber-reinforced units inside the compressed area of the fiber-reinforced composites, then the experimental data are veracious for the material.

Abstract: Fiber- reinforced composites have been applied extensively not only in aero-space, automobile and other industries, but also in sports instruments. The application of fiber- reinforced composites for sports instruments is introduced. The advantage of fiber rein-forced composites, materials selection, products varieties, examples and status of application for sports instruments are discussed.

Abstract: During the cooling process of composites after curing, thermal residual stress will be produced due to mismatch of the coefficients of thermal expansion between matrix and reinforcement phases. Thermal residual stress is one of the most important factors that affect the mechanical properties of composite materials. The effect of fiber volume fraction on the distribution of thermal residual stress in unidirectional fiber reinforced composite has been investigated with finite element analysis. The results show an inhomogeneous distribution of thermal residual stress in different regions of composites. The longitudinal stress on the interface between matrix and fiber is the main factor resulting in debonding failure of composites. This numerical study can be of great significance in designing new composites with high performance.