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Conference Proceedings
Lifetime Prediction of Continuous Fiber-Reinforced Plastics Based on Nonlinear Damage Accumulation
Full Title: LIFETIME PREDICTION OF CONTINUOUS FIBER-REINFORCED PLASTICS BASED ON NONLINEAR DAMAGE ACCUMULATION AND FINITE ELEMENT SIMULATIONS
Abstract:
This paper presents an approach for lifetime prediction of fiber-reinforced plastics based on nonlinear damage accumulation. Already established damage accumulation laws, such as Palmgren-Miner, are to be modified with nonlinear parameters in order to characterize the damage evolution of fiber-reinforced plastics in a more accurate way. For this purpose, cyclic investigations were carried out on glass fiber-reinforced polyurethane with quasi-isotropic layer setup to determine basic mechanical characteristics. The stiffness-based characteristic values, recorded to develop the simulation model, are generated from hysteresis loops, which are also used to calibrate the material model. The experimentally determined stiffness degradation is converted into a damage curve by assigning the first measured value to degree of damage 0 and the failure value to degree of damage 1. Therefore, a hysteresis loop for each degree of damage between 0 and 1 is present, so that a damage dependent stress-strain ratio can be determined and transferred to the material model cali-bration. In addition, a characteristic damage development is derived from the damage curves, whereby the stress level and the influence of sequence can be taken into account for a nonlinear damage accumulation model on global level. Based on the global findings an algorithm is presented that transfers those to the local level in finite element simulations. This approach provides the fundamentals for a lifetime prediction of fiber-reinforced plastics with varying fiber orientations under cyclic loading.
Developing Photopolymerizable Acrylate Resin Formulation for Impact Modified 3D Printed Thermosets
This contribution focuses on engineering photopolymerizable acrylate resin formulations for a superior fracture energy absorption of 3D printed acrylate thermosets. Herein, we report a polydimethyl siloxane-based block copolymer as an impact modifier, compatible with the UV curing process, which undergoes reaction induced phase-separation during the 3D printing process to form a rubbery phase sufficient for enhanced impact properties. A systematic investigation of the effect of concentration of the impact modifier on the morphology of rubbery domains and fracture toughness was conducted. Results show that at an optimum concentration of 15 wt.% and particle size of 57 nm, an order of magnitude improvement in the fracture energy release rate is realized. Fractographic analysis of the impact modified thermosets using optical microscopy indicates the presence of significant plastic deformation in an otherwise brittle material. Notably, the engineered acrylate thermosets, at an optimum concentration, exhibit similar improvements in the impact properties irrespective to the print layer thickness and independent of the crack orientation with respect to the printed interphase. Detailed investigation of the failure mechanisms for impact modified thermosets show that the block copolymer diffuses to the interphase during the 3D printing process, resulting in preferential localization of the impact modifier near the print interphase resulting in an isotropic enhancement of the fracture toughness.
Evaluation of Sub and Near Critical Carbon Dioxide for Low Processing Temperature of Medical Thermoplastic Polyurethane
Incorporation of thermosensitive active pharmaceutical ingredients for manufacturing multifunctional polymeric medical device is still limited as they can be deteriorated in the hot-melt extrusion process. In this study, the potential of sub and near-critical carbon dioxide used as a green plasticiser was injected to hot melt extrusion process of Pellethane thermoplastic polyurethane to decrease process temperature. Its thermal and rheological behaviour were also evaluated. The resultant extrudates were characterised using parallel-plate rotational rheometry and differential scanning calorimetry. The process temperature decreased from 185 to 160 °C. The rheology indicated that the reduction of melt viscosity to 36.36% and 40.04% at 600 and 1000 psi, respectively. The results indicate that the employment of scCO2 as a transient plasticiser is a viable aid to conventional hot-melt extrusion and offer more opportunities for thermosensitive drugs to be more thermally stable in the molten stream of Pellethane thermoplastic polyurethane.
Comparative Study of Filled and Unfilled PLA Produced Via Injection Molding and 3D Printing
This study investigates the impact of two different processing methods, Injection molding (IM) and 3D printing (3Dp), on Neat/unfilled polylactic acid (NPLA) and the short carbon fibers (SCFs) filled polylactic acid (SPLA). Furthermore, the resulting processing conditions and its influence on mechanical properties, such as tensile, flexural, notched Charpy impact test, and heat deflection temperature (HDT) along with the process-induced effects, such as fiber length distribution and voids were studied. The process-induced voids were evident in all the computed tomography (CT) scans, 3Dp specimens have higher void volume fraction compared to no visible voids in IM specimens. Similarly, the mechanical test results such as tensile, flexural and notched Charpy impact test follow the trend for 3Dp SPLA and IM SPLA. On the contrary, 3Dp 0° and ±45° NPLA tensile test results are comparable to IM NPLA, whereas 3Dp 0° NPLA has the highest impact resistance compared to injection molded NPLA and SPLA as well as 3Dp SPLA specimens, indicating the annealing effect induced by the heated 3D printing bed along with increased void volume fraction. Furthermore, the HDT study indicates the maximum serviceable temperature of both NPLA and SPLA remained comparable regardless of the processing method. Moreover, the change in fiber length distribution for SPLA injection molded and extruded filament specimens were negligible.
Failure Analysis Case Study: The Good and the Bad PVC Cable Coatings
Polyvinylchloride (PVC) is the most commonly used thermoplastic resin for electrical cable coatings. PVC that hardens after polymerization is not suitable for insulating and protecting wires and cables. The necessary mechanical, thermal, and electrical levels can only be reached with the addition of softeners, stabilizers, and fillers. Composition of the good and the bad PVC samples were analyzed using FTIR spectroscopy and TG analysis.
It was found that ditridecyl phthalate was used as a softener in both samples. Magnesium oxide was used as a filler in one sample. The higher amount of water that present in the sample at room temperature and evolves during the first stage of PVC decomposition might be responsible for the low heat resistance of one sample.
Effect of Filler Content on the Electrical Conductivity of Graphite Based Composites
This research work addresses the feasibility of employing thermoplastic composites as the substitute material for bipolar plates in a fuel cell. Bipolar plates are vital components of a proton exchange membrane (PEM) fuel cell assembly. Vigorous efforts are directed by manufacturers to reduce the size, weight, and cost of the bipolar plates. The carbon-based composites are comparatively cheaper, lightweight, and can easily be used for the production of bipolar plates. However, the bipolar plate material's electrical conductivity should be sufficient to conduct the electric current from one cell to another. The main purpose of this research was to study the effects of carbon content on the electrical conductivity of the composite material. The composite materials were produced by adding graphite particles into polypropylene matrix at different contents ranging from 60wt% to 84wt%. The through-plane electrical conductivity tests were carried out. While the electrical conductivity of the composites increased by increasing the graphite content. A sudden rise in electrical conductivity was also observed between 76wt% and 80wt%.
Tensile Specimen Preparation Method Impacting Failure Behavior
Sample preparation for polymer testing is an overlooked portion of the test plan and execution. Thermoplastics and thermoset materials offer multiple methods to prepare samples: injection molding, CNC machining, waterjet cutting, die-cutting, and laser cutting are all used often. We test samples of a polycarbonate (PC) material in uniaxial tension and compare results for injection molded, machined, waterjet cut, and diecut samples. All but the diecut samples showed the same stress vs. strain response, though the waterjet samples failed at a significantly lower strain. The die-cut samples showed significant damage on the edge of the specimens, and had a lower yield stress. Careful selection of specimen preparation methods is important to a well-designed test plan.
Filterability of Raven 1300 Ultra Carbon Black For Fine Denier Fiber Applications
Carbon blacks can offer improved performance over dyes in fiber and textile applications in polyester, polyamide and polypropylene resins. Their stringent cleanliness and superior filterability are of critical importance for successful fine denier fiber applications. In this study, the filterability of Birla Carbon’s fiber black Raven 1300 Ultra was evaluated after compounded in PET resin via twin-screw extrusion and a Farrel continuous mixer (FCM).
The carbon black demonstrates excellent filterability performance via twin-screw extrusion and an FCM compounding processes. FCM was explored to make atypical PET masterbatches with higher carbon back loadings beyond 30%. However, a further study focusing on improving dispersion and filterability of highly loaded PET masterbatches is warranted to better serve the fiber application.
Novel Flame Retardants Based on Ionic Liquids for PMMA, PC and TPU Plastics
Inovia Materials LLC is positioned to develop new generation flame retardants and flow enhancers based on ionic liquids, to replace and expand the applications of traditional additives with high “green chemistry” qualities, superior performance and enhanced properties. we have developed new flow enhancers for PC, TPU, TPAE and high-performance plastics: PAR, PPA, PPS, PSU, PEI, PEEK, etc. Our flowing enhancers have superior thermal stability (400 degree C TGA), perfect compatibility (ionic liquids being tailorable), significant increase melt flow index at very low loading level, and mild effects on the physical-mechanical properties of plastics. We welcome product application opportunities from industries.
Blending Scholarly Knowledge and Practioner Know-How To Successfully Injection Mold A Complex Part
A complex piece of sporting equipment was molded to customer satisfaction, meeting critical dimensions despite complicated tooling and the use of a crystalline resin. Combining modern simulation techniques and industry expertise proved to be a winning strategy in solving this challenge. The use of post-molding, warp controlling fixtures was completely eliminated from the legacy production process, leading to improved part performance and plant efficiency.
Comparison of Longevity of PE- and PP-based TPO Waterproofing Membranes
This study compared the longevity performance of polypropylene (PP) and polyethylene (PE) based thermoplastic polyolefin (TPO) waterproofing membranes. It was demonstrated that PE-TPO outperformed PP-TPO for both heat aging and standard UV aging in terms of tensile property retention, weight retention and resistance of surface cracking. Better longevity for PE-TPO is attributed to the lack of tertiary carbon which is intrinsic to PP and prone to chain scission.
Direct Compounding of Long Glass Fiber-reinforced Plastics in the Injection Molding Process
Currently, only specially treated and compacted carbon fiber recycles can be fed into the twin screw extruder. In this paper, different delivery forms of fibers are characterized in terms of the product quality. The differences between the fibers for twin screw extrusion is illustrated.
Evaluation of Mesh Interface and Immersed Boundary Models For the Optimisation of Mixing Elements
Mesh interface and immersed boundary models are presented as simplifications for the simulative design of dynamic mixing elements for single screw extruders. These simplifications have great potential to cut complexity and cost in both drafting and computation. Results for distributive mixing are compared quantitatively and qualitatively to a non-simplified 3D model. It is found that good agreement with the 3D model is achieved when the simplified models’ throughputs are adjusted for mass conservation.
Profile Extrusion Die Balancing Using Polymer Extrusion Simulation Software
The design of an extrusion die has been evaluated utilizing a 3-D polymer extrusion simulation software for optimal flow. The flow pattern, pressure, temperature, and shear rate are simulated in the software. The post-die extrudate shape is also simulated to show the improvement by balancing flow velocity in different sections. The combination of 3-D modeling and simulation decreases the time and difficulties for tuning the die during manufacturing.
Reverse Engineering and Failure Analysis of Materials and Polymers Using Infrared and Raman Spectroscopy
Failure analysis and reverse engineering can greatly expedite product development. Infrared and Raman spectroscopy is the among the most powerful tools for this application because each molecule has a unique infrared and Raman signature. Infrared and Raman microscopy was successfully used to identify foreign particles on elastomers and to depth profile multilayer polymer film. Details of the measurement techniques are discussed.
Stabilization of Polymers for a More Circular Economy
Polyethylene and polypropylene are two of the most easily recycled polymers. Recycling polyolefins can result in downcycling to simple functional polymers, true recycling for reuse in the intended application, or upcycling of the polymer into higher quality products. To take advantage of the available feedstock and improve its utilization, stabilizers are can be added to allow the polymer to retain its original physical properties. A variety of customer-based case studies on recycling and upcycling will be covered showing how additives allow for improvements in the recycle stream.
Use of Gradually Changing Profile Shape in Extrudate Sizers for Simplification of Die Design
Simulation of the flow and extrudate deformation in two extrusion dies with gradually changing profile shape in successive sizers is presented. The change in the profile shape in sizers is used to employ a simpler die geometry and then deform the extrudate in sizers to the required final product shape. Effect of non-uniform exit velocity, cooling shrinkage and shape of sizer profiles on extrudate deformation is included in the simulation. The predicted extrudate shape and layer structure is found to match accurately with those in a coextruded product.
Vibration Welding of Agave Fiber Biocomposites
In this study, the welding of several formulations of injection molded agave-fiber filled biocomposites were studied. A 240Hz vibrational welder was used and weld pressure, amplitude, and weld time were varied to determine their effects on lap shear weld strength. Strength testing was performed with a universal testing machine. The morphology of the weld zones was also analyzed to gain insight into the mechanics of the welding.
3D Chemical Foaming Simulation For Transfer Molding Process
This study presents the recent development of three-dimensional prediction of cross-linked ethylene propylene diene monomer rubber (EPDM) with chemical blowing agent azodicarbonamide (ADCA) in transfer molding process. Plunger retraction is applied after transfer process is completed. The reaction kinetics model, density model, and viscosity model are applied to describe the complex foamed rubber system in the simulation study. The experimental investigation of material properties into EPDM/ADCA system are studied to make physical parameters in simulation model more realistic. The flow front behavior, the density of foamed rubber, the reaction behavior in foaming and curing conversion are examined to understand the dynamic behavior of the rubber material in both transfer and foaming stages. Furthermore, we study the effect of foaming and plunger retraction. Simulation results show that foaming effect make clamp force larger, however, plunger retraction effect make the back flow occur from cavity to pot to avoid high pressure in the cavity and therefore eliminate the mold clamp force. This study is of great relevance to light weighting application and should reduce the product-to-market cycle time by eliminating the need for the traditional trial-error method.
3D Printed Hybrid Composite Structures - Design and Optimization of A Bike Saddle
As designers and engineers continue to push the boundaries of high performance and lightweight design, the use of complex geometries and composite materials is growing. However, traditional composite manufacturing often requires the use of additional tooling and molds which can significantly increase the cost. In this study, a carbon fiber reinforced composite bike saddle is designed and manufactured to demonstrate a newly developed hybrid composite manufacturing process. Using a 3D printed epoxy to print the final part geometry and co-cure pre-impregnated carbon fiber reinforcement, the bike saddle can be optimized, designed and manufactured in less than 24 hours.
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