Elsevier

Wear

Volumes 352–353, 15 April 2016, Pages 24-30
Wear

Effect of fabric orientation and impact angle on the erosion behavior of high-performance thermoplastic composites reinforced with ductile fabric

https://doi.org/10.1016/j.wear.2016.01.016Get rights and content

Highlights

  • These composites obtained in present study are ductile based on their erosion behavior.

  • Erosion behavior was not affected by fabric orientation.

  • We proposed a new model of erosion damage for ductile materials.

  • Obtained mathematical model can accurately characterize their erosion behaviors.

Abstract

How composites reinforced with plain-weave polybenzoxazole (PBO) fibers were eroded by solid particles was investigated. By evaluating the erosion rates of plain polymers and these composites at various impact angles (α=15–90°), we confirmed that the polymers and their composites were ductile. The relationship between erosion behavior and fabric orientation from an energy perspective was studied, and our experimental results agreed well with our analytical results showing that the erosion behavior did not depend on fabric orientation. Using these results and scanning electron micrographs, a mathematical model was produced and it was used to predict the erosion rates of ductile materials. To verify this model, the theoretical and measured erosion rates of three high-performance ductile-fabric-reinforced thermoplastic composites were compared, showing that our mathematical model can accurately characterize their erosion behaviors.

Introduction

Once molded, fiber-reinforced plastics (FRPs) containing thermosetting resin cannot be reformed [1]. Because of this limitation, these plastics are typically disposed of in landfills, which may cause serious environmental pollution. However, the staggering growth of FRP use is fading, and fiber-reinforced thermoplastics (FRTPs)—which are easier to recycle—are slowly displacing FRPs. FRTPs are better materials for many parts in cars and airplanes, among other applications, because of their specific properties, high strain to failure, and high toughness [2], [3]. Some parts of these vehicles reach high velocities (such as the part near aircraft engine or helicopter propellers) and thus produce high temperatures, so they cannot use composite materials made from normal thermoplastic. An attractive candidate for such applications, however, is polyetherimide (PEI): a high-performance amorphous thermoplastic polymer with a glass transition temperature of ~220 °C, high heat resistance, and excellent mechanical properties [4]. Unfortunately, super engineering plastics such as PEI and polyetheretherketone (PEEK) have considerably higher melt viscosities than thermosetting resins and normal thermoplastics, such as polypropylene (PP), because of their high molecular weight, which makes it more difficult for the resin to impregnate the fabric. In the present study, composites were fabricated with lower polymer viscosity by using solution impregnation [5].

Another concern in many aircraft applications is the wear and damage of composite surfaces caused by solid particles in the air [6], which can lead to lengthy maintenance, security risks, and other serious problems [7]. Thus, engineering materials must not only have high specific strength but also resist wear and damage.

For the past few years, many researchers have investigated how highly heat-resistant thermoplastics and their composites eroded by solid particles. For example, Sari et al. manufactured composites from unidirectional carbon fibers and PEI and investigated how their erosion behaviors changed with the particle velocity, impact angle, and surface roughness [8]. Miyazaki et al. made thermoplastic resins reinforced with short carbon fibers and analyzed how the solid-particle erosion behavior depended on the matrix (PI, PEEK), reinforcement fibers, impact angle, and particle velocity [9]. Harsha et al. studied composites made from PEEK and glass fibers, investigating how their fiber content and mechanical properties affected their erosion behavior [10].

The vast majority of these studied composite materials were reinforced with carbon fiber (CF) or glass fiber (GF) [7]. In contrast, there is little research on PBO (polybenzoxazole) fibers, aramid fibers, or other high-performance ductile fibers. These fibers are important to study mainly because aramid and other high-performance fibers have better erosion resistance than carbon fibers and glass fibers [6]. Also, the literature focuses on how unidirectional fiber orientation affects erosion behavior, but almost no work deals with how fabric orientation affects erosion behavior [3], [11], [12], and there are no convenient methods to predict the erosion rate of composites made from high-performance ductile fabrics. With a mathematical model, erosion rates can be predicted with less need for experiments; however, studying the erosion of these composites currently demands substantial time, energy, and materials.

In the present paper, we attempted to fill these gaps. By studying how changes in fabric orientation affected the erosion behavior of composites from an energy perspective, a mathematical model of the erosion rate as a function of impact angle was developed. To verify this model, the erosion behaviors of composites reinforced with high-performance ductile fabrics was studied, and then compared those experimental findings with our predictions. To elucidate the erosion mechanism of ductile materials, the damaged surfaces of one type of composite with scanning electron microscopy was analyzed.

Section snippets

Materials

The reinforcing fabric was PBO, a rigid-rod isotropic crystalline polymer (Toyobo Co., Ltd., Osaka, Japan). It has many advantages over traditional polymers—including high tensile strength, good fatigue resistance, and good resistance to corrosion, heat, chemicals, and salt water—so it has been used in many advanced fields such as the airline, marine, and space industries [13]. PBO fiber has a tensile strength of 5.8 GPa and a modulus of 270 GPa.

Two types of thermoplastic matrix were used:

Effect of impact angle on erosion behavior

The impact angle is important in distinguishing composites. When erosion rate is measured as a function of impact angle, various composite materials respond exhibit different behaviors [16]. In previous work, ductile materials exhibited an αmax of 15–30° and an αmin of 90°, while brittle materials exhibited an αmax of 90° [17]. Beyond these classifications, materials present semiductile behavior. Thermoplastics seem to act ductile, and thermosetting polymers seem to act brittle [17], [18].

Development of the mathematical model

Although several erosion models have been developed for quickly predicting erosion rates, there is almost no research on erosion modeling in thermoplastic composites made from high-performance ductile fabrics [20]. Along with fabric orientation β, only one other variable was studied, impact angle, in our mathematical model; other parameters were set constant. As discussed by Bitter [22], the first important factor to consider is whether the impacting solid particle still has a horizontal

Conclusions

In this paper, the solid-particle erosion behaviors and mechanism of composites were examined and discussed, and the following conclusions are made.

  • 1.

    These composites are ductile based on their erosion behavior;

  • 2.

    Erosion behavior was not affected by fabric orientation. This phenomenon was analyzed from an energy perspective, and our analysis was validated by our experimental results;

  • 3.

    A new model of erosion damage for ductile materials was proposed. The model was divided into two parts to discuss and

Acknowledgment

This work was supported by a Grant-in-Aid for the Shinshu University Advanced Leading Graduate Program by the Ministry of Education, Culture, Sports, Science and Technology (MEXT), Japan.

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