Papers by Keyword: Thermoplastic

Abstract: In this study online-capable dielectric analysis techniques were investigated to show its potential on the example of detecting phase transitions of polyamide 6 (PA6) and its composites. The differential scanning calorimetry (DSC), a standard testing method commonly applied in thermophysical analysis, is used as a reference method throughout this work. Dielectric measurement techniques are introduced as a means for providing an online measuring concept that is able to monitor phasechanges in both neat, as well as glass and carbon reinforced PA6. Whereas a simple sensor setup has proven to be adequate for dielectric measurements of neat and glass reinforced PA6, the insertion of an additional insulation layer between sample and sensor was necessary to overcome short circuit problems induced through the conductive nature of carbon in carbon fiber reinforced PA6.Results show that crystallization and melting can be successfully identified using dielectric analysis and can be compared directly with results from the DSC. Analysis in the dielectric method is based on relative permittivity ϵ′, loss factor ϵ′′ and ion viscosity ρ. Here phase changes can be observed as a frequency dependent step in the measurement signal, which becomes increasingly apparent with increasing frequency. Plotting the first derivative of ϵ′, ϵ′′ and ρ relative to the temperature the phase change can be depicted in form of a peak, similar to the case of DSC. The derivative signals can be used as a direct means for monitoring in manufacturing processes.

Abstract: Compression molding of near net-shaped rib-stiffened plates has been performed for a parametric investigation on the filling behavior of chopped woven flake reinforcements. The experimental investigation showed that different aspect ratios of ribs can be filled completely within the tested maximum ratio of flake size to rib opening width of 6.25 and a maximum consolidation pressure of 15 bar. However, defects such as voids, non-impregnated regions and fiber matrix separation may arise depending on the combination of parameters and a mechanical jamming effect caused by the woven architecture of the flakes. A tendency for a limiting consolidation pressure is observed based on the fiber matrix separation. The ability to re-use thermoplastic prepreg cutting waste has been demonstrated.

Abstract: This paper presents the investigation of a thermoplastic cross-ply sheet for use in manufacturing small arms protective helmets. The material system contains four unidirectional layers oriented in a [0°/90°/0°/90°] configuration. This advanced composite is wholly thermoplastic, consisting of ultrahigh molecular weight polyethylene (UHMWPE) fibers within a polyurethane matrix. Due to the polymeric nature of the constituent materials, the mechanical behavior of the composite system will have a dependence on forming temperature. The shear characterization of the prepreg and the investigation of the factors influencing the representative shear stiffness including sample geometry, strain rate, conditioning and temperature are discussed.

Abstract: The ability of a draping simulation to accurately predict the outcome of a forming process mainly depends on the accuracy of the input parameters. For pre-impregnated composites, material must be characterised in the same conditions as forming occurs, i.e. in temperature regulated environment. Given the issues encountered while testing specimens enclosed in a thermal chamber and mounted on a tensile testing machine, new test methods have to be developed. A new approach using a Dynamic Mechanical Analysis system is presented for the investigation of tensile properties perpendicular to fibre direction of unidirectional pre-impregnated composites. Analyses are focused on a unidirectional carbon fibre thermoplastic tape reinforced polyamide 6 in its molten state. Quasi-static tests are performed at forming temperature for different loading rates with specimens of different geometries in order to assess the reproducibility of the test method.

Abstract: This paper compared three representative traditional industrial countries, the United States, Japan and Germany, the research and development and usage of thermoplastic composite. At the same time discusses the future research and application of the thermoplastic materials.

Abstract: The incorporation of electronic circuitry into additively manufactured thermoplastic parts is a highly desirable innovation enabler. Applications include embedding signal traces into custom air or ground vehicle components, creation of complex interconnect devices exploiting the design freedom of 3D printers, or as a way to create various grounding, shielding, sensing or antenna patterns on custom structures. Stratasys has explored multiple approaches for creating selective metallization on 3D printed plastic parts. Earlier publications [1] described evaluations of metal-based ink deposition methods such as ink jet and aerosol jet. More recently we have explored the use of Laser Direct Structuring, (LDS) thermoplastic resins in our 3D printers. With LDS technology, parts are selectively metallized after 3D part build through a laser imaging and electroless plating process. Finally, some early feasibility work has been attempted using inherently electrically conductive materials. In this paper, the various methods evaluated for integration of metal traces with 3D parts will be discussed, along with part examples and performance comparisons.

Abstract: Traditional medical external fixation material represented by gypsum is brittle, heavy and prone to adverse reactions, clinical effect is not ideal. The pine wood fiber particles (size for 10 ~ 40 mesh) and polycaprolactone (PCL) are used to prepare a new kind of wood-plastic polycaprolactone composites (WPC) by the blending method. The experimental results show that the increase of PCL mass ratio can enhance the material strength and flexibility, especially the match force between the pine wood fiber particles. Meanwhile, when the mass ratio of PCL reached 65%, this enhancement effect significantly diminished; after the mass ratio of PCL reached 70%, the phenomenon of material mechanics performance decline. In this paper, the prepared WPC, which can soften under temperature 50°Cand repetitively finalize the design, have good mechanical properties, low-temperature thermoplastic and environment protection.

Abstract: This article describes the analysis of the three types of heating metallic meshes used for the resistance welding process of thermoplastic matrix composites. The analysis of the heating that takes place in the mesh will carry to optimize the process parameters and to assure a correct joint and properties in the whole area.

Abstract: Defects and shape distortions can arise during thermoforming of thermoplastic composites. Design guidelines for thermoplastic composites can help to prevent such defects. The material selection and geometry definition are part of the design guidelines. A test to check the formability of a material is developed as an aid for the material selection. Strips of varying widths are thermoformed inducing double curvature, in order to find the width at which the material starts to wrinkle. The thermoformed strips of quasi-isotropic UD carbon/PEEK and quasi-isotropic 8HS glass/PPS show a clear difference in formability. The UD carbon and the 8HS glass strips develop wrinkles through-the-thickness of the laminate at a width of 40 mm and 90 mm respectively. The test shows good potential to be used as part of the design guidelines.

Abstract: This paper presents a novel test set-up to characterize the bending behavior of UD laminates in thermoforming conditions. An analysis of the set-up and the applied boundary conditions is presented. A validation of the test procedure using purely elastic specimens, shows its potential to accurately measure bending properties, to be used for numerical forming simulations. Preliminary bending tests were performed on UD carbon PEEK specimens, showing a visco-elastic response. The actual bending phenomenon is confirmed to be intimately related to the intra-ply shear deformation mechanism.