Papers by Keyword: Polymer Matrix Composite (PMC)

Abstract: A study concerning the application of fiber laser to perforate thermoplastic pre-pregs is presented. An IPG fiber laser was used to drill arrays of holes in PEKK carbon-fiber composite pre-preg material. Perforated holes were of the order of 100μm. The effects of laser perforation process parameters including the number of pulses on the geometry of the resultant holes and the thermal damage to the matrix and fibres have been investigated. Dimensional analysis and experimental results have been used to construct the laser perforation process model. Keywords: Laser perforation; Fibre laser; Process modelling; Polymer matrix composites.

Abstract: In this study the tensile static and fatigue behaviour of a woven-fabric laminate is investigated in both the on-axis and off-axis material directions. Emphasis is placed on the development of damage and its influence on the stress-strain behaviour of the laminate. The test results illustrate that there is a high degree of anisotropic behaviour due to anisotropic damage development, which is evident by the variation of the material behaviour between the on-axis and off-axis test specimens. The fatigue tests also suggest that the on-axis specimens exhibit noticeable stiffness degradation, while the off-axis specimens do not. The qualitative results provide significant insight into the type of damage mechanism responsible for the observed behaviour.

Abstract: This paper focuses on the optimization of ball milling as a dry mixing method and comparison with the wet method for manufacturing phenolic/multi-wall carbon nanotube (MWCNT) composites. In the ball milling, the effect of milling-time on the properties of composites containing functionalized and pristine MWCNT in two MWCNT concentrations has been investigated. At first in the wet method, polymer was dissolved in acetone and then mixed with MWCNT by sonication method. Also, the effect of functionalization by use of acid nitric refluxing was considered. The material properties were characterized by the DSC, FTIR, Raman, electrical conductivity, SEM, TEM and bending strength analyses. The results of electrical conductivity and bending tests showed that the best time for ball milling is about 2 hrs. In addition, functionalization had a positive effect on bending strength and a negative effect on electrical conductivity. The results of DSC indicated that the composite manufactured by ball milling method resulted in more thermal stability than that manufactured by the wet method. It was also shown that the functionalization increases the thermal stability; however, the increasing MWCNT concentration leads to agglomeration, thereby decreasing the thermal stability.

Abstract: The influence of the rice husks powder (RHP) content and its particle size distribution on the composite’s tensile strength, fracturing elongation ratio, flexural strength and flexural elastic modulus has been investigated. Respective water absorption and thermal properties of PP composites incorporated with different proportion of RHP have also been analyzed. The microstructure of fractured surfaces was further observed in scanning electron microscopy (SEM). The results showed that the composites with RHP of 245 μm have higher mechanical properties. The tensile strength and fracturing elongation ratio decrease with the increase of RHP content, and reach peak values in 30% RHP content. Water absorption and volume expansion ratio of the composite increase with the increasing of RHP content. Flexural strength and flexural modulus decrease after water absorption. When PHR content is low, the RHP particles are well distributed and the interface of RHP and PP is smooth. When PHR content is higher, the RHP particles tend to agglomerate, leading to poorer interface and lower mechanical properties, the composite failed with brittle fracture.

Abstract: In this work, a methodology to quantify the effect of the drilling operation, during the application of the incremental hole-drilling technique (IHD) for measuring residual stresses in laminate composites, in particular, the polymer matrix composites (PMC), is presented. This technique will allow the optimization of the drilling procedures and its parameters, enabling the quantification of the drilling effect. This quantification is obtained by using an experimental calibration procedure followed by a numerical simulation of the whole process. The direct comparison of the experimental and numerical results will allow quantifying the effect of the drilling operation. As example, the methodology was applied to the case of carbon/epoxy cross-ply laminate [0°/90°]_5s. The holes have been made by using two different drilling procedures, but the same tool geometry. High speed milling powered by air compression, a process usually employed in the case of the application of hole-drilling technique to metal alloys and a conventional computer numerically controlled (CNC) milling machine, were used. The results seem to show that incremental hole-drilling could be a reliable technique to determine residual stresses in fibre-reinforced polymers.

Abstract: In the past decade, natural fibre composites with thermoplastic matrices had attracted many composites manufactures for the superiority of lightweight and low-cost. A major challenge for natural fibre composites was to achieve high mechanical performance at a competitive price. Composites constructed from yarn and fabric structure preforms were better than composites made from random nonwoven mats. However, the twist structure of conventional ring spun yarns prevented the full utilization of fibre mechanical properties in the final composites. In this paper, the wrapped yarns were produced by wrap spun method with flax and polypropylene (PP), in which all flax fibres were twistless, then woven to be fabric preforms. The PP fibres served as a carrier for flax fibres during processing and became the polymer matrix in the final composites. The homogenous distribution of fibre and thermoplastic matrix in preforms could be achieved before hot pressing, so that not lead to impregnate difficultly, and prevented damage to the reinforced nature fibres during processing. Composites made from the wrapped yarn demonstrated significant tensile and peeling properties. The fabric structures (include plain, twill, and basket weave) and yarn tensile orientation (in 0°, 90°, 45°), had great influence on tensile strength and elongation of preforms. The cavity thickness of hot pressing mould had different influence on the tensile strength and peeling strength of thermoplastic composites, and the mechanical properties were superior when the thickness was 0.8-1.2 mm. The microstructure of thermoplastic composites showed uniform infiltration between layers, and had good bonding interface between flax fibre and PP matrix in composites.

Abstract: To explore the dynamic impact fracture behavior of nanoparticle-reinforced composites, a bottom-up numerical method was proposed and verified through the fracture process simulation of nano-SiO2/epoxy sample in Charpy impact test. At the nano-scale, a parametric micromechanics model having interphase was built. And the effective material properties of the nanocomposites with variant volume fractions were obtained. Based on the homogenization theory, the macro-scale model of impact sample was established. It is demonstrated that this proposed bottom-up method can predict the locations and directions of cracks at macro-scale, and the growth process of rupture can also be visualized dynamically. The impact strength obtained from this method has a good agreement with the measuring results in literature. And this simulation method can also be used as an assistant tool for comparing the crack propagation rate of nanocomposites with variant particle contents.

Abstract: Particulate composites with crosslinked polymer matrix and solid fillers are one of important classes of materials such as construction materials, high-performance engineering materials, sealants, protective organic coatings, dental materials, or solid explosives. The main focus of a present paper is an estimation of the macroscopic Young’s modulus and stress-strain behavior of a particulate composite with polymer matrix. The particulate composite with a crosslinked polymer matrix in a rubbery state filled by an alumina-based mineral filler is investigated by means of the finite element method. A hyperelastic material behavior of the matrix was modeled by the Mooney-Rivlin material model. Numerical models on the base of unit cell were developed. The numerical results obtained were compared with experimental stress-strain curve and value of initial Young’s modulus. The paper can contribute to a better understanding of the behavior and failure of particulate composites with a crosslinked polymer matrix.

Abstract: A stable and high lubricant ultrathin film was fabricated by self-assembled procedure at room temperature. Thickness of the films was regularly increased with the layer-by-layer self-assembly process in which poly (acrylic acid)-ferric hydroxide (PAA-Fe(OH)3) sol as anion polyelectrolyte and photosensitive diazoresin (DR) as cationic polyelectrolyte. And the process which based on electrostatic attraction was verified by UV-vis measurement. Furthermore, the ionic bonds in the films converted to covalent bonds under UV irradiation. Finally, the surface morphology and microtribology of the films were investigated by atomic force microscopy (AFM) and friction force microscopy (FFM). The results indicate that the films are flat and uniform through the self-assembly technique and the surface friction coefficients maintain at a rather low value.

Abstract: A biodegradable films were prepared by blending sodium lignosulfonate (LS) with poly(vinyl alcohol) (PVA) and with borax as cross-linking agent, in an aqueous system. The suitable process conditions of preparing the blend films with good water-resistance and mechanical properties were determined by single-factor experiments. SEM, FT-IR, TGA and DSC analysis were performed to examine the contribution of LS and borax to the properties of the blend films. The results indicated that the introduction of a moderate LS mass ratios to PVA from 1/8 to 4/8 in the blend films could simultaneously enhance the tensile strength of blend films up to 43.98MPa. SEM showed that the intermiscibility of blend films was satisfactory with appropriate LS. Studies of the water sorptive capacity of the materials suggested that the water sorptive capacity at equilibrium less than 17% and water-resistance improved. The results of TGA indicated blend films have greater thermal stability than the pure polymers.