Safety and Its Ethical Challenges for the Christian Engineer in a Technological Society

In every major corporation safety is a high priority and corporate policy statements stress the company’s commitment to keep people and the environment safe. However, safety comes at a cost. Corporations are in business to make profits by providing quality products and services for consumers at affordable prices. Engineers play a critical role in the design, construction, and operation of corporations across the globe and are constantly challenged to find new ways of doing things in order to reduce operating expenses in a competitive global economy. Companies must keep pace with the latest technological innovation or face the prospects of going out of business. Constant economic pressures put engineers in positions to make tough decisions about where to cut costs. When safety is compromised for economic reasons or any other reason, people and the environment are at risk. For the Christian engineer, these ethical decisions may be different and rise to a higher standard than that required by a corporation’s code of ethics[1]. A Christian engineer motivated by faith in God and acting on biblical principles will often reach different conclusions from those operating strictly from a corporate business model based on maximizing profits. Philosophical ethical systems fall short of the Biblical ideal[2]. In facing ethical challenges related to safety, the Christian engineer should propose strategies and standards that follow from the command, “Love your neighbor as yourself.” [1] Martin, M., & Schinzinger, R. (1996). Ethics in Engineering. New York: McGraw-Hill. [2] Holmes, A. F. (2007). Ethics: Approaching Moral Decisions. Downers Grove, IL: InterVarsity Press

DYNAMIC RELAXATION PROPERTIES OF AROMATIC POLYIMIDES AND POLYMER NANOCOMPOSITES

The dynamic relaxation characteristics of Matrimid® (BTDA-DAPI) polyimide and several functionalized aromatic polyimides have been investigated using dynamic mechanical and dielectric methods. The functionalized polyimides were thermally rearranged to generate polybenzoxazole membranes with controlled free volume characteristics. All polyimides have application in membrane separations and exhibit three motional processes with increasing temperature: two sub-glass relaxations (ƴ and β transitions), and the glass-rubber (α) transition. For Matrimid, the low-temperature ƴ transition is purely non-cooperative, while the β sub-glass transition shows a more cooperative character as assessed via the Starkweather method. For the thermally rearranged polyimides, the ƴ transition is a function of the polymer synthesis method, thermal history, and ambient moisture. The β relaxation shows a dual character with increasing thermal rearrangement, the emerging lower-temperature component reflecting motions encompassing a more compact backbone contour. For the glass-rubber (α) transition, dynamic mechanical studies reveal a strong shift in Tα to higher temperatures and a progressive reduction in relaxation intensity with increasing degree of thermal rearrangement. The dynamic relaxation characteristics of poly(ether imide) and poly(methyl methacrylate) nanocomposites were investigated by dynamic mechanical analysis and dielectric spectroscopy. The nanoparticles used were native and surface-modified fumed silicas. The nanocomposites display a dual glass transition behavior encompassing a bulk polymer glass transition, and a second, higher-temperature transition reflecting relaxation of polymer chain segments constrained owing to their proximity to the particle surface. The position and intensity of the higher-temperature transition varies with particle loading and surface chemistry, and reflects the relative populations of segments constrained or immobilized at the particle-polymer interface. Dielectric measurements, which were used to probe the time-temperature response across the local sub-glass relaxations, indicate no variation in relaxation characteristics with particle loading. Nanocomposite studies were also conducted on rubbery poly(ethylene oxide) networks crosslinked in the presence of MgO or SiO2 nanoparticles. The inclusion of nanoparticles led to a systematic increase in rubbery modulus and a modest positive offset in the measured glass transition temperature (Tα) for both systems. The sizeable increases in gas transport with particle loading reported for certain other rubbery nanocomposite systems were not realized in these crosslinked networks

Corrosion fatigue of a superduplex stainless steel weldment

Superduplex stainless steels have superior mechanical and corrosion properties compared to austenitic stainless steels such as the grade 300 series. This is a result of a microstructure consisting of roughly equal percentages of austenite (y) and ferrite (a) and negligible inclusion content. As a result, super duplex stainless steels are increasingly being used in the offshore oil and gas industries. It is also envisaged that they will find application in the emergent renewable energy sector in areas such as offshore wind, wave and tidal electricity / hydrogen generation. Corrosion fatigue (CF) conditions are expected in such applications. Of critical concern are weld joints where inherent sub critical surface/embedded flaws diminish crack initiation resistance enhancing the probability of subsequent crack propagation. The current research investigates the CF crack propagation performance of weld metals produced by two welding techniques. Since sub sea components are always cathodically protected, this condition was simulated in the CF tests. In addition, high positive potentials were simulated, as this condition is possible in the absence of cathodic protection. One weldment was completed using the expensive and relatively slow gas tungsten arc (GTA) welding method. The other weldment was achieved using the GTA method for the root pass and subsequently filled using the cheap and relatively quick shielded metal arc (SMA) welding method. The resultant crack propagation life was derived from the crack propagation tests by means of a numerical model. Fatigue life of the weld metals (assuming negligible residual stress influence) is similar to standard design curves for class D, carbon and carbon-manganese structural steel butt welds. Thresholds for the onset of crack growth in Zeron 100 base and weld metals are similar and were shown by means of the numerical model to correspond with the endurance limit specified in the standard design curve. Cathodic over protection is much more deleterious than high positive potentials above a critical stress level for Zeron 100 base and weld metals leading to an increase in crack propagation rates on average by a factor of 4.3 over rates in air. The GTA root/SMA fill weld metal performs equally well as the GTA root/GTA fill weld. Therefore, a potential economic saving is evident. Finally, a new model for hydrogen assisted subcritical brittle crack propagation in ferrite is proposed

Holy Alliance? Navigating Evangelical Political Identity in the Era of Donald Trump

Evangelical Christians have always had a complex relationship with political issues in the United States, especially with the rise of the Christian right in the 1980s. Pastors and church leaders function as crucial communicators of political values in a contemporary American context. Since 2017 the Trump presidency has provided a new set of issues to consider. With Festinger’s (1957) Cognitive Dissonance theory and Tajfel’s (1981) Social Identity theory as the foundation, this study examines how evangelical Christian pastors conceptualize their religious and political identities, how they communicate with their congregants about political issues and how they handle differences between their political and religious opinions. Six pastors from a mid-sized, Midwestern university town were interviewed using a semi-structured format. Findings are explored in the context of Cognitive Dissonance theory and Social Identity theory

Effect of Environmental Conditioning on the Properties of Thermosetting and Thermoplastic-Matrix Composite Materials by Resin Infusion for Marine Applications (PREPRINT)

Glass-fibre reinforced polymer (GFRP) laminates were manufactured using Vacuum assisted Resin Transfer Moulding (VaRTM) with a range of thermosetting resins and a novel infusible thermoplastic resin as part of a comprehensive down-selection to identify suitable commercially available resin systems for the manufacture of marine vessels greater than 50 m in length. The effect of immersion in deionised water and in an organic liquid (diesel) on the interlaminar shear strength (ILSS) and glass transition temperature (Tg) was determined. The thermoplastic had the highest Tg of all materials tested and comparable ILSS properties to the epoxy. Immersion in water, however, caused larger reductions in ILSS properties of the thermoplastic compared to the other systems. SEM showed a transition from matrix-dominated failure in the dry condition to failure at the fibre-matrix interface in the wet and organic-wet specimens. The overall performance of the infusible thermoplastic is good when compared to well-established marine resin systems; however, the environmental performance could be improved if the thermoplastic resin is used in conjunction with a fibre sizing that is tailored for use with acrylic-based resin systems

Retention of Mechanical Properties After Water Immersion for Glass-Fibre Polymer Composite Laminates with Thermoset & Thermoplastic Infusible Resins

In this work, we conducted an extensive comparative study of the water absorption behavior and retention of mechanical properties of a group of GRP composite laminates manufactured with a range of infusible thermosetting and thermoplastics resins. All laminates were manufactured by Vacuum-Assisted Resin Transfer Moulding (VARTM; the most relevant manufacturing technique in shipbuilding) with a range of state-of-the-art thermosetting resins (Urethane acrylate Crestapol 1210, Epoxy SR1125, Bio-epoxy Supersap CLR, Phenolic Cellobond J2027X) and a novel infusible acrylic thermoplastic resin (Acrylic Elium 150). The reinforcement of choice for each laminate was a unidirectional glass fabric of 996 gsm. Sample preparation for water immersion studies was according to ASTM D5229. This study was part of a comprehensive down-selection of commercially available resins in terms of their suitability for shipbuilding applications, as part of the EU H2020 project FIBRESHIP2 .  A selection of relevant properties of the laminates with different resin systems is presented in this paper including fibre volume fraction, apparent interlaminar shear strength (dry and wet condition), flexural strength (dry and wet condition) and flexural modulus (dry and wet condition)

Thermoplastic infusible resin systems: candidates for the marine sector?

This work investigated the feasibility of the use of a novel infusible thermoplastic resin (Elium 150 from Arkema) for composite laminate manufacture by resin infusion methods and possible application in the shipbuilding sector. We compared the properties of Elium glass-fibre laminates with those of laminates infused with state-of-the-art thermosetting epoxy and urethane acrylate resins. The Elium laminates matched the mechanical performance (flexure and interlaminar shear strength) of the epoxy and surpassed that of the urethane acrylate counterpart. However, the mechanical performance of the Elium laminates after immersion in water at 35 oC for 28 days deteriorated compared to urethane acrylate, but was comparable in flexural properties to that of the epoxy. The combination of superior mechanical performance coupled with acceptable environmental resistance and comparable composite laminate manufacturing conditions makes the infusible thermoplastic a possible future candidate matrix over commercial thermosetting resin options

Mechanical evaluation of a fire retardant through-thickness reinforced sandwich structure for marine applications

One of the main restrictions in adopting polymer composite materials for primary and secondary structural applications in marine vessels over 50 meters in length is concerns regarding fire retardancy and also a lack of design guidelines in general. The aim of this study is to evaluate the edgewise compression strength and core-shear strength of a fire retardant sandwich structure reinforced with through thickness composite ‘bridges’ under ambient conditions. These properties are important for structural components subjected to in-plane loads such as bulkheads. Core shear strength of the through-thickness reinforced sandwich far exceeded non-reinforced sandwich. However, edgewise compression strength and stiffness of the reinforced case was found to be similar to the unreinforced case

Bio-based epoxy resin systems as potential alternatives to petroleum based epoxy matrices in marine fibre-reinforced polymer composites

Fibre-reinforced polymers (FRP) are extensively used in the marine industry for the manufacture of lightweight hull structures for vessels up to 50m in length, and for secondary structures and components in larger vessels. The main benefits resulting in the application of FRP in shipbuilding include: significant weight reduction resulting in substantial fuel saving, increase in cargo capacity and subsequent reduction of greenhouse gas emissions, improved life cycle performance and reduced maintenance costs due to corrosion resistance. As the use of thermoset polymers in shipbuilding increases, so too does the interest in finding suitable alternatives to the use of petroleum-based raw materials. Much work has been published on bio-based epoxy resin systems from natural raw materials, such as vegetable oils, however, the mechanical performance of the bio-based resin systems in comparison to equivalent petroleum-based systems is not widely documented. This research focusses on the comparison of petroleum-based and bio-based two-part commercial epoxy resin systems to manufacture glass fibre reinforced polymers (GFRP) for marine applications. Laminates were manufactured using the Vacuum Assisted Resin Transfer Moulding (VARTM) manufacturing process. Specimens were mechanically characterised in order to evaluate fibre volume fraction, density, apparent inter-laminar shear strength, flexural modulus and strength. The effect of water ingress on the mechanical properties of laminates was also studied by soaking samples in water at 35°C for 28 days. Specimen quality and fracture surfaces were assessed using optical and scanning electron microscopy. Initial results have shown that the average apparent inter-laminar shear strength of the petroleum-based samples was almost identical to the bio-based samples (within 1%), while the flexural strength and modulus of the petroleum-based samples was only 6% and 7% higher than the bio-based samples. Despite the comparatively good mechanical performance of the bio-based laminate, the high viscosity of the resin resulted in higher infusion temperatures and longer infusion times than for the petroleum-based epoxy

Retention of Mechanical Properties After Water Immersion for Glass-Fibre Polymer Composite Laminates with Thermoset & Thermoplastic Infusible Resins

Glass-fibre reinforced polymer (GRP) composite materials are the most widely adopted amongst fibrereinforced polymer composites globally, with approximately 1 million tons produced annually in the EU alone. GRP’s find very wide use and application in a number of industrial sectors (e.g. land & waterborne transport1 , marine, construction) due to their excellent balance between good performance and low cost compared to fibre reinforced polymers utilising other commercially available fibres (e.g. carbon, aramid). Particularly in marine applications, durability of composites and their ability to exhibit unchanged performance and stability in a marine context and environment is a crucial factor in order to select the most appropriate combination of polymer matrix and reinforcement. Ideally, a composite would retain its mechanical and thermo-mechanical profile even when exposed to a marine environment for extended periods. In this work, we conducted an extensive comparative study of the water absorption behavior and retention of mechanical properties of a group of GRP composite laminates manufactured with a range of infusible thermosetting and thermoplastics resins. Sample preparation for water immersion studies was according to ASTM D5229. This study was part of a comprehensive down-selection of commercially available resins in terms of their suitability for shipbuilding applications, as part of the EU H2020 project FIBRESHIP2 . All laminates were manufactured by Vacuum-Assisted Resin Transfer Moulding (VARTM; the most relevant manufacturing technique in shipbuilding) with a range of state-of-the-art thermosetting resins (Urethane acrylate Crestapol 1210, Epoxy SR1125, Bio-epoxy Supersap CLR, Phenolic Cellobond J2027X) and a novel infusible acrylic thermoplastic resin (Acrylic Elium 150). The reinforcement of choice for each laminate was a unidirectional glass fabric of 996 gsm. A selection of relevant properties of the laminates with different resin systems is presented in this paper including fibre volume fraction, apparent interlaminar shear strength (dry and wet condition), flexural strength (dry and wet condition) and flexural modulus (dry and wet condition). For the wet condition, samples were immersed in distilled water for 28 days at 35 oC (wet state) in accordance with classification society guidelines. The quality of the laminates (void content, fibre-matrix adhesion) was examined by scanning electron microscopy on fracture surfaces. The effects of water absorption on the microstructure, mechanical, thermal & thermomechanical properties of the laminates were studied. The average water absorption percentage varied across all resins systems from 0.19 to 1.37% in the interlaminar-shear specimens, and from 0.25 to 1.59% in the flexure specimens. The phenolic laminate was the one absorbing most water in both cases but the mechanical properties were relatively unaffected. Fibre volume fraction was in the range 0.56 to 0.6 for all of the laminates. The majority of the tested GRP laminates showed good retention of their flexural properties and interlaminar shear strength under the testing conditions. The laminate that appeared to be most adversely affected was the infusible thermoplastic, showing a reduction in flexural strength and interlaminar shear strength of 17.3% and 37.5%, respectively (in comparison to the dry state values). However, the water absorption for the Elium 150 was not excessive, ranging from 0.40 to 0.42% for the ILSS and flexure samples, respectively. References: 1 Summerscales J, Marine applications of advanced fibre reinforced composites, Woodhead Publishing, Cambridge, 2016 2 H2020 project FIBRESHIP, funded by the European Commission under GA 723360 (www.fibreship.eu