Papers by Keyword: Thermoplastic Composite

Abstract: This article examines the prediction of wrinkling initiation in self-reinforced thermoplastic composite materials for potential application in rapid forming of this class of materials. Whilst most of recent researches concentrate on examining metallic wrinkling behavior, this article aims to introduce a wrinkling indicator for composite sheet. The material system involved in the study is a self-reinforced polypropylene woven composite with a fiber orientation of 0°/90° along the warp and weft directions. Square specimens were stretched uniaxially along diagonal direction until the onset of wrinkling. It is observed that when the wrinkling occurs, strain increment ratio exhibits an abrupt change. This fundamental observation leads to the prediction of onset of wrinkling by using abrupt changes in strain increment ratio as a metric.

Abstract: In this work, experiments were conducted to examine the impact of fiber orientation of self-reinforced polypropylene on wrinkling phenomenon. Defects due to wrinkling are major quality issues in rapid forming of sheet materials. This article examines the influence of two fiber orientations [0°/90° and 45°/-45°] on wrinkling initiation of a self-reinforced polypropylene composite (Curv®) material system. It was found that 45°/-45° specimen wrinkles at smaller axial displacement compared to 0°/90° specimen. In both specimens, there was an abrupt change in strain increment ratio that corresponded to the onset of wrinkling. This phenomenon validates the robustness of the wrinkling indictor based on strain increment ratio concept.

Abstract: An experimental investigation of the resistance welding of PPS/carbon fiber is presented in this manuscript. Currently, one of the main problems of the structural polymer composites consists in its effective integration of the components. The electrical resistance welding has been considered as one of the promising techniques for bonding composites, because it is a quick process with easy surface preparation. To improve the process to welding poly-(phenylene sulfide) (PPS) reinforced with carbon fiber laminates, it was used a full factorial design (2³). Considering the factors pressure, electrical current and time, the more appropriate conditions for welding were evaluated based on a criterion of maximum lap shear strength, according to ASTM D1002-10. A comparison between welded and non-welded specimens in terms of analysis dynamic mechanical (DMA), thermomechanical analysis (TMA) and vibration tests was performed. It was demonstrated that large-scale DMA presented a similar results but according to TMA and vibration test were observed that welded specimens presented different results when compared to non-welded laminates, due probably to the presence of metallic heating element.

Abstract: A modern lightweight design with dissimilar materials such as metals in combination with fiber-reinforced polycaprolactam represents a possible lightweight variant in the automotive body shop. One of the issues arising from the use of polycaprolactam is its hygroscopy. The collected moisture evaporates out during the curing of the adhesive in the paint drying process and causes the adhesive to foam up. This leads to a decrease of the structural bonding strength. Many different factors, such as waterjet cutting processes, transportation and storage in undefined environmental conditions before the gluing process, as well as the flushing bath of the painting pretreatment, can contribute to the component humidity.Based on the common lap-shear test, this essay presents the influence of the substrate humidity on the bonding strength as well as possible pretreatment methods to avoid or decrease the negative influence of the substrate humidity. Using infrared radiation or atmosphere plasma localized at the bonding spot, the substrate begins to dry resulting in a bond with better bonding strength. For the future it is planned to test other options like laser substrate drying, adhesive modifications with regard to viscosity and moisture catcher enrichment.

Abstract: We present in this paper, the coupling of heat transfer to the crystallization of composite in a closed mold. The composite is based on thermoplastic resin (low viscosity PA 66) with glass fiber (50% volume fraction). In order to realize this coupling, an accurate characterizationof thermo physical properties in process conditions, especially in the molten and solid state is needed. In addition, theidentification of the parameters of crystallization kinetics is required. Therefore, we present the methods that were used to study the thermo physical properties as the thermal conductivity, heat capacity and the specific volume. Moreover, the kinetic of crystallization was estimated over a large temperature range by using Flash DSC and classical DSC. In order to validate the measurements, the whole process was modeled by finite elements. The model includes the resolution of the strong coupling between the heat transfer and crystallization. Finally, the experimental and numerical results were compared.

Abstract: Glass wool is discontinuous glass fiber with the average diameters of 3-4 μm produced by means of centrifugal process, and mainly applied to heat and acoustic insulation. But, there are few reports on glass wool applied to reinforcement of plastic materials in which chopped strand made by chopping continuous glass fiber is used primarily. In this study, the polyamide 66-based composite material samples containing glass wool were prepared and its wear property as a mechanical property was evaluated. It was found that the composite has an advantage on the wear property compared with a conventional glass fiber reinforced plastic, and the result suggests that glass wool has a possibility as a reinforcement material applied to plastic parts required wear resistance.

Abstract: This article explains and demonstrates how to first and second injection moulding influence to shrinkage effect of polypropylene composites with talcum and cutting glass fiber. Results show that the longitudinal and transverse shrinkage changed by differend parameters of injection moulding. It was observed shrinkage compensating effect occurring at composite molded parts with a high glass fiber content. Recycling process has reduced the shrinkage and tensile strength. Caused an increase in elongation, but it has not noticed any major changes in the hardness of injection molded parts.

Abstract: The present work investigates the effect of natural weathering on polypropylene (PP) composites containing short glass fibers and talc. The samples of PP composites obtained by injection moulding were submitted to nine months of natural ageing (from March to November 2012). It observed effects of climatic conditions on some physical properties such as hardness, longitudinal and transverse shrinkage as well as plastic and elastic deformations.

Abstract: This study presents the evaluation of selected mechanical tests of polymer composites which were re-processed. Materials Valox PBT (with 30 % glass fibre) and Celanex® 2004-2 PBT (without filler) and their regranulate were used at tests. The material PBT - regranulate PBT compositions investigated were 100/0, 80/20, 60/40, 30/70 and 0/100. Samples from PBT were prepared by injection molding and their mechanical properties were tested by tensile test and Shore hardness test. The material made from 100% recycled material compared to the baseline had a decrease in tensile strength and Shore hardness value hasn’t changed. Failure of the samples was also observed by SEM. Utilization of regranulate at the production of new moulded parts are important from aspect of reduction plastics waste and pollution abatement of environment.

Abstract: In previous studies [1, , we have presented a detailed formulation of a macroscopic analytical model of the optical propagation of laser beams in the case of unidirectional thermoplastic composites materials. This analytical model presented a first step which concerns the estimation of the laser beam intensity at the welding interface. It describes the laser light path in scattering transparent composites (first component) by introducing light scattering ratio and scattering standard deviation. The absorption was assumed to be negligible in regard to the scattering effect. In this current paper, in order to describe completely the laser welding process in composite materials, we introduce the absorption phenomenon in the model, in the absorbing material (second component), in order to determine the radiative heat source generated at the welding interface. Finally, we will be able to perform a three dimensional temperature field calculation using a commercial FEM software. In laser welding process, the temperature distribution inside the irradiated materials is essential in order to optimize the process. Experimental measurements will be performed in order to valid the analytical model.