Papers by Keyword: Interphase

Abstract: Integrated leading edge protection (InLEP) is a novel LEP method that involves co-bonding a tough thermoplastic to the blade shell of the wind turbine made of fiber-reinforced thermoset polymer. In the co-bonding process, as a result of the interdiffusion of the bonded thermoplastic and thermoset polymers, an interphase is formed between them. An important factor affecting the level of interdiffusion is the cure temperature. In this work, we investigate the influence of cure temperature on the interphase morphology and bond strength of ABS-polyester/glass and PC-polyester/glass hybrid composites. The hybrid composites are manufactured via vacuum-assisted resin transfer molding. Interphase morphology is observed and the interphase thickness is measured via optical microscopy. Bond strength is tested via climbing drum peel testing and subsequently, fractography analysis is carried out on the fractured samples. It was found that both the interphase thickness and bond strength decrease with an increase of cure temperature. The decrease in bond strength at high temperatures was accompanied by an increase in the extent of interfacial failure, while interphase failure at low temperatures promoted higher bond strength.

Abstract: A finite element model on the single fiber pull-out test of short fiber reinforced rubber matrix sealing composites (SFRC) were established. The effects of the interphase properties on the interfacial stress distribution and initial debonding strain are investigated based on the cohesive zone model (CZM). The influences of interphase thicknesses and elastic modulus on the interfacial debonding behavior of SFRC are obtained. The results show that the interfacial initial debonding strain increases with the increasement of interphase thickness, and it decreases with the increasement of interphase elastic modulus. An interphase thickness of 0.4 μm and an interphase elastic modulus of about 750 MPa are optimal to restrain the initiation of the interfacial debonding.

Abstract: Chemically curing adhesives are formulations requiring reactions to convert from liquid to solid. Once cured, these adhesives carry the potential to create strong load bearing joints, resisting even severe detrimental service conditions. In adhesively bonded joints with chemically curing adhesives the term "interphase" relates to the adhesive volume adjacent to the surface of the adherent (interface), which generally will exhibit properties different from those of the adhesive bulk polymer. The properties of these interphases play an important role concerning the performance and durability of structural adhesive joints. Therefore localized strain analysis in the cross-section of shear-loaded adhesive joints was performed by combining a high-precision mechanical testing device with digital microscopy and by developing a method for preparing, marking, and digitally tracking the local deformations in micro shear specimen. Non-uniform shear profiles developing in the cross-section of the adhesive joints after exceeding the yield point serve as a sensitive indication for mechanical surface-affected interphase properties and it could be observed, that deranged crosslinking promotes strain softening of the polymer in the interphase. Infrared analysis of the cross-sectional interphase region in adhesively bonded joints was performed with a Bruker Tensor II Fourier Transform Infrared (FTIR) spectrometer equipped with a Hyperion 3000 microscope with a 20x ATR germanium crystal objective and a MCT-Focal-Plane-Array-Detector (FPA), allowing to conduct high resolution chemical imaging and localized chemical analysis.

Abstract: Using stiff particles mixed into polymer matrix may significantly improve global mechanical response of the composite. Unfortunately, this process leads to other side effects, for example, presence of stress concentration at the particle-matrix interface or negative influence on the fracture toughness. The paper presents an approach to estimate the influence of particles on the micro-crack propagation. Material properties of matrix and particles were estimated experimentally. A two-dimensional computational model was proposed and all calculations were done in software ANSYS. On the base of linear elastic fracture mechanics, the influence of the particle shape on the micro-crack propagation paths was analyzed via numerical studies. The results of numerical simulations show that the shape of the particles can significantly influence the micro-crack path as well as the stress intensity factor on the crack tip, which corresponds to fracture toughness of polymer composite filled with rigid particles. The conclusions of this paper could contribute to better understanding of the behavior of the polymer composites.

Abstract: In order to reduce cost of production and decrease environmental pollution, so many research work has been conducted and still ongoing as to the possibility to use kenaf fiber in high technologies production. Its shows that kenaf fiber have potential reinforced fiber in thermosets and thermoplastics composites. This paper presents the various of challenges to produce kenaf as a reinforcement which mean to identify the limit of kenaf fiber performance after over all of challenging factor. The main factor that touch on interphase, water absorption, chemical treatment and fiber fraction which mean affect the performance of kenaf fiber as a reinforcement are discussed.

Abstract: Suitable mechanical properties of composites are very important for light low energy constructions. Their specific properties can offer high specific strength, but current composite properties are not at maximum level, and therefore the efforts of development on further improving are focused. Properties of composites depend not only on character of a matrix and reinforcement, but also on properties of an Interphase between these components. Experimental and numerical analysis dealing with the mechanical properties at the micro level for new types of energy-efficient fiber composites with reduced environmental impact has been compiled. For numerical analyses a finite element method (FEM) was used. Analyses were focused on the cohesion and stress at the interface of the system fiber-matrix-core. From the results can be seen that the specific orientation of the reinforcement relative to the direction of applied force significantly affects the resulting elastic modulus. When investigating the delamination of the layers, the influence of the fiber orientation of the reinforcement is evident. Also quality of the interface has a crucial influence.

Abstract: In order to address the problem of stiffness and mechanical properties, a micromechanical approach for the prediction of the overall modulus of nanocomposites (Nylon-6/nanoclay/silica) using a self-consistent scheme based on the double-inclusion model and taking into account the different morphologies exfoliated or intercalated of the nanoparticles. Self-consistent approach that is used in our calculations was explained after reviewing the inclusion of Eshelby, in particular the double inclusion and while considering also the effect of constrained region, modeled as an interphase around reinforcements. Namely, polyamide 6 reinforced with clay platelets and silica particles. Several parameters on the Young's modulus of the composite were studied to see the effect of having mixed two or three reinforcements in polymer matrix. Finally, we demonstrated the process undertaken for the calculation of elastic constants of the material studied.

Abstract: In recent years, particle reinforced composites are widely used due their mechanical properties as construction materials, high-performance engineering materials or protective organic coatings. The paper was mainly focused on the estimating of the interactions of the micro-crack and the particles in the particulate polymer composites. A non-linear material behavior of the matrix was obtained from the experiment and it was used to investigation by means of the finite element method - using ANSYS software. A two-dimensional numerical model was developed and a micro-crack propagation direction was calculated based on the assumption of the linear elastic fracture mechanics. The results indicated that the presence of the interphase between particle and matrix can improve the fracture toughness of the polymer particle composites through debonding process. The paper can contribute to a better understanding of the behavior and failure of the composites with the polymer matrix reinforced by the rigid particles.

Abstract: The effect of sterilization on the structural integrity of the polydimethylsiloxane (PDMS) matrix composite reinforced with carbon fibers (CF) is investigated by nanoindentation test. We present the investigation of the influence of sterilization processes on fiber/matrix interphase properties. The effect of multiple widely-used steam sterilization processes on fibers/matrix interphase region properties was studied by modulus mapping test.

Abstract: In this study we present the investigation of the influence of multiple sterilization processes on micromechanical properties carried out on a composite based on carbon fibers (CF) and polymer matrix composite polydimethylsiloxane (PDMS). The effect of widely-used steam sterilization process on fibers/matrix interphase region properties was studied by nanoindentation.