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Multi-material hybrid structures that blend continuous fiber thermoplastic composites with lower-cost options such as chopped fiber thermoplastic composites and metals is an attractive proposition for many industries, due to the potential dual benefits of lower weight and cost. High confidence in performance predictions is one of the key enablers to convert this potential into successful industry adoption. However, chopped and continuous fiber thermoplastic composites pose numerous challenges for accurate predictions, due to the inherent complexity of the material behavior. To establish confidence in predictions, a test component was designed that can be produced in a representative production process and can validate all of the many different composite failure modes. Predictive simulation procedures in multiple industry-standard commercial software platforms were established to cater for the needs from multiple industries and loading scenarios. Component level static and dynamic tests were performed on the test component and were compared with the simulation results to validate the methodology. Excellent correlations between the simulation model and the physical test results paves the way for using the methodology for yet-to-be-designed components.
The ambition of developing innovative and technically high-quality products is one of the main reasons for the growing use of fiber-reinforced plastics (FRP) in industry. In particular, the opportunity to combine lightweight construction with a high degree of design freedom and functional integration leads to the preferred use of composite materials in the automotive and aerospace industries.During the operation time the composite parts are exposed to continuously changes of environmental influences which lead to aging of the polymers. This includes frequent temperature changes, dampness, saline media and mechanical loads for instance. The aging effects, caused by the interaction with the surrounding media, result in various changes of the material properties. Strength losses, embrittlement, degradation of the molecular weight or optical changes are some examples which can occur during the aging process and may induce a prematurely failure of the composite parts.In order to predict the life time of those components, the effects of the aging process and the influences on several material properties have to be known. Hence, in the following the environmental aging of a woven fabric reinforced, a short glass fiber-reinforced and an unreinforced polyamide 6 will be investigated and the influences on the material properties will be characterized.
Flexible thermoplastic polyurethane/reduced graphene oxide (TPU/rGO) nanocomposite sheets are prepared via in situ vitamin C reduction. X-ray photoelectron spectroscopy spectra suggest a successful reduction of the GO by vitamin C, which can enhance the interfacial polarization ability of the resultant rGO layers. X-ray diffraction patterns and transmission electron microscopy image indicate a well exfoliation of the rGO layers in the TPU matrix. This results in the formation of a rheological percolation structure in the nanocomposite with 0.75 vol% rGO, as suggested by the rheological properties. The enhanced interfacial polarization ability and the formed percolation structure of the rGO layers in the TPU matrix allow for constructing a large network of micro-capacitors. Thus high dielectric permittivity (ε′ = 151 at 1 kHz) is obtained for the nanocomposite sample with only 0.75 vol% rGO.
Today continuous fiber thermoplastic composites are used in various applications across the industry due to its excellent mechanical properties, which offer significant weight saving potential. In addition, thermoplastic composites are well suited for mass production and easily integrated in a hybrid overmolding processes. This enables the industry to manage cost while delivering performance. Forming or draping is an important step in the manufacturing of continuous fiber prepreg or tape based thermoplastic material forms. Different studies indicate that forming of multi-layer unidirectional (UD) laminates may result in out-of-plane wrinkling and in-plane fiber misalignment. Thus, understanding the forming behavior and having a simulation method in place for its prediction is essential for widespread acceptance of this new material. This paper presents experimental forming studies on multi-layer GF-PP UD thermoplastic composite laminates. The influence of the tool geometry and the laminate layup on forming behavior are studied. The results show that the current GF-PP UD composites are easy to shape, resulting in a large processing window. However, in some cases process induced defects arise, such as out of plane deformation, fiber waviness, ply splitting, bridging, etc. whose influence on part performance needs to be assessed and quantified. Forming simulations are performed on UD tape based laminate composites in PAM-FORM software using a visco-elastic material model, dedicated to continuous fiber composites. Numerical studies show that the predicted process induced defects such as fiber waviness and wrinkling patterns are in good agreement with experiments. With increased confidence on such a computational framework, thermo-forming simulations can help identify critical spots in the product and process design at an early stage and reduce costly product development times. Keywords— Continuous fiber composite, Unidirectional composite, Thermoforming, Wrinkling, Ply splitting, Marcelling, Numerical simulation
Cellulose nanocrystals (CNCs) are routinely produced as aqueous suspensions. These are then typically freeze-dried in order to be added into polymeric composites using melt-blending. However, dispersing freeze-dried CNCs into hydrophobic polymers is a challenge. In this study, our objective was to advance our understanding of the impact of freeze-drying methods on the morphology of dried cellulose nanocrystals (CNCs), and on the tensile properties of the resulting PLA-CNC nanocomposites. CNCs were prepared as aqueous suspensions with 10.7% solids content using a sulfuric acid method, and freeze-dried using a procedure typical to our laboratory. In addition, the CNC aqueous suspension was diluted to 1% and directly freeze-dried or sonicated for 10 or 30 minutes, flash frozen, and freeze-dried. The particle size and morphology of the CNCs before and after freeze drying were determined by microscopy. CNCs were then incorporated into PLA using melt-blending extrusion and injection molding. The PLA-CNC nanocomposites were tested for thermal and mechanical properties. Before freeze-drying, CNCs were nano-scale, while agglomerations were observed after freeze-drying. The agglomerate sizes were reduced with dilution and/or increased sonication time, with fibrillar structures observable after sonication. PLA-CNC composites containing CNCs that were subjected to dilution, sonication for 30 minutes, flash frozen and freeze-dried had higher tensile modulus and strength compared with the other treatments.
Hybrid composites with two or more fillers offer advantages such as improved mechanical properties and balanced performance/cost ratio. They have been increasingly used in many industries such as automotive and aerospace industry. The properties of hybrid composites largely depend on the matrix material, the type and the content of fillers, the filler distribution in the matrix, and the interfacial bonding between the fillers and the matrix. Wood fiber (WF), glass fiber (GF), and carbon fiber (CF) have been used in a variety of polymer composites applications. This study applies the injection molding process, and investigates the tensile properties, water absorption, burning behavior, and surface roughness of pure polypropylene (PP), PP/WF composites, PP/GF composites, PP/CF composites, PP/WF/GF hybrid composites, and PP/WF/CF hybrid composites. This study would provide guidance for choosing composites for different applications in consideration of cost and performance.
Fabrication of graphene-based poly(ethylene terephthalate) (PET) nanocomposites through in-situ polymerization is demonstrated. With the goal of improving the incorporation and dispersion of graphene in the PET matrix, an ultrasonic exfoliation method was employed in ethylene glycol (EG), a raw material used in PET synthesis. The graphene EG dispersions were used as precursors to fabricate PET nanocomposites. Transmission electron microscopy (TEM) was used to evaluate the level of exfoliation of graphene in the dispersions. Mechanical testing showed at 2 wt. % concentration of graphene, the elastic modulus and the tensile strength of PET increased by 22% and 10%, respectively. Differential scanning calorimetry (DSC) measurements were performed to evaluate the percent crystallinity, and it was observed that addition of graphene at 2 wt. % increased the crystallinity of PET by 33%. Scanning electron microscopy (SEM) and X-ray diffraction (XRD) were used to study morphology and microstructure of the PET nanocomposites, respectively.
Progressive failure analysis is herein used to study the damaged deformation up to ultimate failure in prepreg platelet-based tensile coupons with stochastic morphology. Computational damage mechanics approaches (continuum and discrete) are utilized for constitutive modelling and addressing complex interacting/competing damage mechanisms. The developed failure analysis allows for virtual characterization of how the composite structure details, meaning the platelet geometry and system morphology (geometrical arrangement and orientation distribution of platelets), define the effective properties of a platelet-molded composite system, its stiffness, strength and variability in properties.
This study investigates the effects of tris(nonylphenyl) phostite (TNPP) on the mechanical property of bacterial polyester, poly(3-hydroxybutyrate-co-hydroxyhexanoate) (PHBH). Two types of PHBH were used: One has 5.6 mol% of 3-hydroxyhexanoate (3HH) (PHBH5.6) and the other has 11.1 mol% of 3HH (PHBH11.1). PHBH/TNPP samples were prepared by melt-compounding and injection molding, and TNPP content varying from 0 to 3wt%. Tensile test results suggested that the addition of TNPP slightly decreased Young’s modulus and strength of both PHBH5.6 and PHBH11.1. However, the addition of TNPP influenced strain at failure and fracture energy of the two types of PHBH in a different manner, that is, significant increase of strain at failure and fracture energy for PHBH11.1, in contrast to decrease of strain at failure and fracture energy for PHBH5.6. The results suggest that TNPP can be used as an additive to significantly improve ductility and fracture energy of PHBH with high 3HH content.
This study evaluates the morphological, fracture and mechanical characteristics of composites of epoxy with carbon nanofibers (CNFs). These composites were prepared via modified solvent exchange process resulting in significant filler dispersion and matrix filler adhesion as evidenced from the SEM micrographs. Composites with 0.1, .5, and 1t% fillers were evaluated. The crack resistance, KIC of these composites with just 1wt% CNF is more than 2 times that of neat epoxy. The tensile strength and modulus of the epoxy CNF composites show more moderate changes with increase in the CNF content.
Damage induced surface texturing (DIST) is a newly developed technique based on fiber de-bonding and pullout in composite materials. This method consists of two stages - in the first stage fibers are aligned longitudinally in the compliant material and during the second stage, the composite is cut perpendicular to the direction of aligned fibers to generate the textured surface. Characterization of the produced composite demands thorough investigation of process parameters like matrix and fiber stiffness, fiber geometry, fiber volume percent ratio. In the present study, surface textured composites are produced using polydimethylsiloxane (PDMS) as the compliant material, which has been reinforced with various fibers to manipulate the surface functionality of the cut surface. The results indicate that increasing fiber elastic modulus, fiber diameter and fiber tensile strength will increase de-bonding and pullout length. In contrast, enhancing critical strain energy release rate (G2c), matrix modulus, the friction coefficient between fiber and matrix and fiber/matrix misfit strain can decrease de-bonding and pullout length. Furthermore we show that increased de-bonding and pullout lengths impart the generated surfaces with increased hydrophobicity.
Acoustic performances are commonly required by different industries, such as building and construction, automotive and others. Based on the specific application, the requirements and also test methods can be significantly different from one area to another. Flame retardant performance represents another type of commonly specified requirement as well, and this kind of performance also shows significant dependence on test methods, which are determined by the applications. In this paper, two new grades of light weight reinforced thermoplastic (LWRT) composites are introduced. Acoustic performance tested by ASTM E1050 and ASTM C423-17 methods, and flame retardant (FR) performance tested by ASTM E84 and SAE J369 methods will be discussed. The physical properties and mechanical properties of the new composites will also be compared with the standard LWRT materials.
Over the last few decades, the move towards more sustainable development and environmental protection has offered many opportunities to develop both biodegradable and biobased composite materials with excellent performance. This new class of materials promises to enable the circular economy concept and sustainable development for our future. In this work, the properties comparison between renewable bioresourced fillers and synthetic conventional fillers were presented and discussed. This works reveals that biocarbon-filled poly(butylene terephthalate) (PBT) hold very high potential to replace existing mineral filler-filled PBT composites in automotive applications. With high biobased content, lower density and cost, it is obvious that the biocarbon filler can be used as a substitute for conventional fillers to develop more eco-friendly products.
In this work, simultaneously strengthened and toughened high density polyethylene (HDPE) composites were successfully prepared by the self-designed loop oscillating push-pull molding (LOPPM) machine. A series of related characterization methods were used to investigated the properties of resulted samples. The tensile strength, impact strength and Young's modulus of LOPPM samples was dramatic increased compared to the CIM samples due to the existence of aligned shish-kebab, demonstrating a simultaneously reinforced and toughen HDPE-based sample was obtained. SEM and 2D-WAXD results indicated that the incorporation of complex dynamic shear force field and UHMWPE induced the highly crystal orientation and thus regular shish-kebab was observed. According to the relationship of structure and properties, the mechanism of simultaneously strengthened and toughened was discussed and provide a controlled way to manipulate the congregated structure of crystalline polymer via external dynamic force field.
This study investigates the effects of screw configuration of the second extruder on the thermal properties of glass fiber reinforced polyamide 6 (PA6) composites throughout the direct long-fiber reinforced thermoplastic (D-LFT) process. Two screw configurations, which generate low and high shear stress in composite melts, were applied to the second twin-screw extruder in the D-LFT process. Thermogravimetric analyses (TGA) and differential scanning calorimetry (DSC) analyses were performed on samples taken from different locations along the D-LFT process. TGA results showed that thermal stability of the final products can be improved by decreasing shear stress in composite melts in the second extruder. Non-isothermal DSC crystallization analysis revealed no substantial changes to the material’s degree of crystallinity with the variations in screw configuration. Isothermal DSC crystallization analysis also showed that the screw configurations had little effect on crystallization half-time of the final products.
Laser welding to join thermoplastics is used in a wide range of applications because it is a non-contact heating method with short cycle times. and lower cost. For both surface heating and through transmission heating, carbon black is the most frequently used colorant. It was found that carbon black types that have low particle aggregation and distribution were most effective for laser heating. Experiments with laser line beam scanning showed that a slight tilt in the laser head could produce different heating when traveling forward as compared to backward. For dissimilar polymer joining, it was found that surface texturing increased the adhesion joint area and the amount of mechanical interlocking resulting is superior joints.
Factory automation is quickly becoming more common place in today’s manufacturing sector. With labor shortages and rising wages; factories want to automate pad printing to replace workers. Unfortunately, most companies are not doing this because of technical and commercial reasons. Pad printing machines have evolved into complex pieces of equipment many with precision movements with guide rails and servo motors. However, over 95% of pad printing machines are loaded by on operator. An operator will feed the parts into the machine and take them out at the end of the cycle. Pad printing can be more challenging to automate than other processes due to the diversity of products that can be run in one machine and the sensitivity of the inks to the process. Pad printing is behind on the automation of loading parts into a printer. Many companies have developed high level machines with vision systems, rotating fixtures, high speed movements, auto unload, etc… but the system is still loaded by an operator. This operation can many times use more than just the loading operator because there must be someone to bring raw goods to the machine, take finished goods away from the machine, and tend to the inks and other needs of the printing equipment. It takes little imagination to realize that one operator can run a cell like this if the material were automatically loaded and unloaded from the print system. A common answer for this is feeder bowl technology. Many times, feeder bowls are a good solution for this type of situation, however, this is a large investment and it is dedicated to a particular product. Most managers are looking for more diversity in their solutions and want to be able to change things later, this makes a feeder bowl a limited solution. By using robot technology, one can automate the loading of the work cell and have a flexible solution. A robot can be set up with memory and be used to perform many different tasks if the proper job is put into the memory. The capital cost is still there, but the dedicated solution becomes a diverse solution that can utilized for many different projects.• Details to fill in:o Methods of delivery product to a robot Conveyor with camera to tell robot where product is Conveyor with dead stop nest • Both of these systems can be tied to an injection molding machine Tray• Stack up and stack downo Different styles of robots and their specific capabilities 6 axis SCARA Gantryo Technological advancements in pad printing to allow for full automation Automatic ink viscosity Tape clean Camera inspectiono Other reasons why full automation is better than an operator Consistency Productivity Speed
Ultraviolet (UV) and low energy electron beam (ebeam) curing technologies are often grouped together. Both technologies are used to initiate the rapid polymerization of the monomers and oligomers contained in photopolymer coatings, inks and adhesives in a process referred to as "radiation curing" or "energy curing." This presentation will discuss the fundamental differences between UV and ebeam curing technologies and include a discussion regarding the typical differences in formulations and curing equipment configurations commonly used for UV versus ebeam applications. The presentation will then focus on the evolution of low energy ebeam applications and its “miniaturization” over the past decade. Ebeam piezo inkjet printing along with electrophotographic printing and embellishment applications for indirect food contact filmic packaging will be discussed. This presentation will discuss the variety of visual and tactile affects that can be achieved with ebeam finishing for flexible packaging applications using both 100% solid and waterborne photopolymer chemistry. The presentation will then review inline and near line standalone integration options for ebeam which focus on extending the future application potentialof ebeam into 2D and 3D functionalized surfaces which incorporate printed electronics.
Difficult to bond plastics, such as polyolefins and fluoropolymers, are commonly used in various industries for some of the following reasons: the cost of the materials and their inherent chemical and thermal resistance. It can be challenging for manufacturers to find solutions to join these difficult to bond materials together.This paper will provide background information on difficult to bond materials, review techniques for quantifying the surface energy of a plastic, review the latest solutions for surface modification and introduce innovative adhesive solutions to meet the challenges ofbonding these specific substrates.
One common method for the manufacturing of electronic systems with a high resilience is the encapsulation of metal inserts using assembly injection molding. Due to the exposure of such parts to different mediums such as oil or saltwater during use, ensuring tightness still is a challenge. This paper deals with the assembly injection molding of tight electronic systems using microstructures on the metal insert introduced by a one-step electrochemical treatment. It can be shown that the electrochemical treatment increases both the tightness and the strength of the bond between metal insert and polymer component. Furthermore, the effects of the electrochemical treatment on the surface and geometry of the metal insert are presented.
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