The SPE Library contains thousands of papers, presentations, journal briefs and recorded webinars from the best minds in the Plastics Industry. Spanning almost two decades, this collection of published research and development work in polymer science and plastics technology is a wealth of knowledge and information for anyone involved in plastics.
An instrumented hot end has been developed to monitor the pressure in Fused Filament Fabrication, and is used as an in-line rheometer to characterize the viscosity of an acrylonitrile butadiene styrene (ABS) material. Additional analysis was performed on the transient pressure data to consider compressibility effects and nozzle drool. The range of flow rates was identified at which the pressure in the hot end was most stable. Stabilization time given compressibility effects was also evaluated.
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.
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.
Thermal analysis is an important group of tests used in the analysis of plastics and other polymeric materials. It consists of a family of well-established techniques that evaluate material properties as they change with temperature, time, and ambient environment under conditions of thermal programming. The results of thermal analysis tests provide qualitative and quantitative information about the material being evaluated. In particular, this information is important to address plastic failures or in characterization of the material composition and physical properties. The upcoming webinar on thermal analysis will introduce the four primary techniques:
Environmental stress cracking (ESC) is the leading cause of plastic component failure, and a recent study suggests that 25% of plastic part failures are related to ESC. If you deal with plastic components, then “Environmental Stress Cracking of Plastics” will provide you with information that will enhance your understanding of the interaction between chemicals and plastic resins, with the goal of preventing part failure. ESC is a solvent-induced failure mode in which a plastics crack through contact with a chemical agent while under stress. The webinar will be presented from a practical viewpoint with actual case studies to illustrate the ESC mechanism and explain plastic performance. Topics covered during this session include:
Thermoplastic resins are utilized in many applications because of their unique property set, including their ductile response to applied stress. This ductility is associated with the viscoelastic nature of polymers and is attributed to their unique molecular structure. In spite of that inherent ductility, most plastic components fail through one of the many brittle fracture modes. Experience through conducting thousands of plastic component failure analyses has shown that less than 5% were associated with ductile overload. The remainder represent brittle fractures of normally ductile materials. Thus, within evaluations of plastic component failures, the focus of the investigation frequently turns to identifying the nature of the ductile to brittle transition. This relatively brittle response to stress is evident through the examination and characterization of the fracture surface morphology. There are numerous factors, associated with material, processing, design, and service conditions that influence a ductile-to-brittle transition within plastic materials. These include:
Material selection is one of the fundamental aspects that will determine the success or failure of a product. With so many choices available today regarding plastic materials, it is imperative that anyone involved in product design or material selection understand resin properties and how they will affect end product performance as well as part design and manufacturability. While plastic material selection is a frequent topic of discussion, it is not as simple as it may first appear. A thorough understanding of the short-term and long-term properties of the potential plastic resins is essential. To help make the best plastic resin choice, is also essential to have a basic knowledge of polymer chemistry. This webinar will address some of the considerations that need to be made when selecting a plastic resin, and outline the challenges and benefits of selecting an appropriate material. The presentation will introduce a method of systematic selection that will optimize the plastics material selection process.
The need to secure plastic components is prevalent in the manufacture of assemblies in many industries. Joining plastic components to other plastic parts or metal parts often involves the use of mechanical fasteners, such as screws, inserts, or rivets. The joining of plastic parts is inherently more complicated than assembling two metal components because of the fundamental differences in physical properties, including strength, chemical resistance and susceptibility to creep and stress relaxation. Case Studies will be presented to illustrate failures associated with the interaction between plastic components and metal fasteners. The presented cases will illustrate how the failure analysis process was used to identify the failure mechanism as well as the primary factors responsible for the failures. The cases depict representative failures involving varied designs and service conditions.
Cracking occurred within the housing for a piece of weather monitoring instrumentation being used as part of field service trial. The cracking was observed within the bosses used to secure the housing section to the mounting hardware. The focus of this investigation was the determination of the nature and cause of the failure. The results obtained during the evaluation of the failed housing indicated that the cracking occurred through three separate mechanisms. Significant factors in the failure included aspects of design, manufacturing, and the service conditions. This paper will review the testing performed to characterize the failure modes and identify the causes of the cracking, while demonstrating the analytical procedures used in the investigation.
Failure analysis of polymer coating systems can be challenging due to the fact that coating systems typically involve multiple and generally very thin layered components. The root-cause for the failure of a polymer coating can be attributed to many factors. Thus, it cannot be easily determined by inspection or observations, and significant amount of testing is often required to determine the root cause for the failure. Typically, failures can be caused by selection of improper coating system, or it can be caused by insufficient surface preparation, or it can be caused by application related issues. This paper attempts to provide a guide to performing failure analyses of polymer coatings by discussing two separate coating systems that utilized a polyvinylidene fluoride (PVDF) top coat and evaluates the fundamental root causes of failure. The importance of reviewing background information, performing site-inspections, conducting relevant laboratory and field testing, and utilizing published literature to reach a root-cause for the failure is high-lighted. In both cases, laboratory examinations revealed that while high performance coatings were utilized, their compatibility within the system and their susceptibility to hazards within their respective applications, were not accounted for, leading to poorly designed coating systems that eventually failed.
Most engineers and designers come from the metal world. Therefore, many of them make assumptions on the predicted performance of plastic properties based on their metals background. Unlike metals, the knowledge of color and appearance is extremely important in the case of plastics. Most plastic parts have dual functions— physical performance and aesthetics. Aesthetics are important since very few of the parts need to be painted or otherwise decorated if designed and manufactured with due diligence. On the other hand, even if we are designing the most aesthetically critical metal components such as exterior automotive parts, we mostly choose the metals and alloys based on the physical properties, weight, and cost. The aesthetics are left to the paint specialist, who will in most cases find a paint system (primer, paint, and application method) that will meet the cost, durability, and cosmetic requirements. In other words, aesthetics and physical properties are quite independent of each other. A vast majority of metal parts meet their aesthetic and environmental requirements just by getting brushed, plated, chromate conversion coated or anodized. Plastic parts not only need to meet the short-term color and appearance requirements, but also need to be resistant to long term color shift and fading. This paper is in two parts. Part 1 - Appearance and Color Factors - Material - Design - Tooling and Processing Part 2 –The fundamentals of Color and Appearance, Specifications, Measurement and Tolerances
In many instances, failure of polymer-based articles is attributed to chemical interaction with metals or metallic compounds. Indeed, the stability of polymers is often modified by these species; however, their effects on the degradation of polymers are complex and influenced by many factors. This paper reviews known polymer degradation mechanisms and how metals may influence them, discusses deactivators and their role use as stabilizers in polymer formulations, provides literature-based vignettes describing example scenarios where metal-accelerated degradation of plastics may contribute to failures, and provides commentary regarding potential future areas of work in the field.
In the field of mechanical engineering technical elastomers are indispensable due to their material properties. They are often used to avoid load peaks and to influence the vibration behavior of dynamically loaded systems, because of their damping characteristics. Therefore, one field of research constitutes the damage accumulation and lifetime prediction. This paper presents the validation of the virtual lifetime prediction model method, which was developed at the institute of product engineering at the University of Duisburg-Essen. The lifetime is defined as the number of load cycles till the global damage reaches the value 1. This damage is calculated by a failure criterion based on the change of a characteristic value like the dynamic stiffness degradation from a finite-element (FE) simulation. The virtual lifetime prediction method uses a combination of a damage-dependent material model (Yeoh-Model) and a nonlinear damage accumulation model (nlSAM). Both models are calibrated by means of experimental data from dynamically loaded elastomer components. The nlSAM computes the local damage for each finite element depending on material stresses and pre-damage. The dynamic stiffness degradation is a result of locally changed material properties in the FE simulation due to the damage of each element. Finally, the lifetime prediction for unknown loads and different component geometries of the elastomer is carried out, which shows good agreement with the experimental data of the same material batch.
If you work with plastic components that include outdoor exposure, then "Ultraviolet (UV) Effects on Plastic Materials" will provide you with information that will enhance your understanding of the interaction between UV radiation-based weathering and plastic resins, and help prevent premature failure. Topics covered during this session include an introduction to UV degradation and an explanation of the failure mechanism characteristic of UV radiation/plastic interaction. Case studies associated with UV radiation exposure will be presented.
You will learn…
Fourier transform infrared spectroscopy (FTIR) is a fundamental analytical technique for the analysis of organic materials. It provides critical information in the evaluation of polymeric materials, including material identification, contamination, and degradation. The webinar will present a fundamental understanding of the technique and the following topics will be covered:
The injection molding process is one of the key characteristics that determines how a plastic part will perform in service. Manufacturers certainly attempt to avoid failure, but often unanticipated factors result in unexpected problems. The chances for a successful application can be significantly increased through preventative measures, including appropriate material selection, proper mold design, and process development. Even when appropriate actions are taken, failures can still occur. The evaluation of these failures provides an opportunity for learning. By understanding how and why a plastic component is failed, steps can be taken to prevent future occurrences. Case Studies will be presented to illustrate failures associated with the deficiencies from the injection molding process. The presented cases will illustrate how the failure analysis process was used to identify the failure mechanism as well as the primary factors responsible for the failures.
When a plastic part fails, a tough question is often asked, “Why are a limited number of parts failing?”. This is particularly true with seemingly random failures at significant, but low, failure rates. Two aspects are generally linked to such low failure rates, multiple factor concurrency and the statistical nature of plastic failures. Failure often only takes place when two or more factors take effect concurrently. Absent one of these factors, failure will not occur. Plastic resins and the associated forming processes produce parts with a statistical distribution of performance properties, such as strength and ductility. Likewise, environmental conditions, including stress and temperature, to which the resin is exposed through its life cycle is also a statistical distribution. Failure occurs when a portion of the distribution of stress on the parts exceeds a portion of the distribution of strength of the parts. This webinar will illustrate how the combination of multiple factor concurrency and the inherent statistical nature of plastic materials can result in seemingly random failures.
Dynamic Mechanical Analysis (DMA) is a thermoanalytical technique that measures the stiffness (modulus) and damping (tan delta) of polymeric materials to assess the viscoelastic properties as a function of time, temperature, and frequency. Polymeric materials display both elastic and viscous behavior simultaneously, and DMA can separate these responses. Polymers, composed of long molecular chains, have unique viscoelastic properties, which combine the characteristics of elastic solids and Newtonian fluids. As part of the DMA evaluation, a small deformation is applied to a sample in a cyclic manner. This allows the material’s response to stress, temperature, and frequency to be studied. The analysis can be in several modes, including tension, shear, compression, torsion, and flexure. DMA is a very powerful tool for the analysis of plastics and can provide information regarding:
Any article that is cited in another manuscript or other work is required to use the correct reference style. Below is an example of the reference style for SPE articles:
Brown, H. L. and Jones, D. H. 2016, May.
"Insert title of paper here in quotes,"
ANTEC 2016 - Indianapolis, Indiana, USA May 23-25, 2016. [On-line].
Society of Plastics Engineers
Note: if there are more than three authors you may use the first author's name and et al. EG Brown, H. L. et al.
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