A Response Surface Methodology Approach to Improve Adhesive Bonding of Pulsed Laser Treated CFRP Composites

In this work, a response surface-designed experiment approach was used to determine the optimal settings of laser treatment as a method of surface preparation for CFRP prior to bonding. A nanosecond pulsed Ytterbium-doped-fiber laser source was used in combination with a scanning system. A Face-centered Central Composite Design was used to model the tensile shear strength (TSS) of adhesive bonded joints and investigate the effects of varying three parameters, namely, power, pitch, and lateral overlap. The analysis was carried out considering different focal distances. For each set of joints, shear strength values were modeled using Response Surface Methodology (RSM) to identify the set-up parameters that gave the best performance, determining any equivalent conditions from a statistical point of view. The regression models also allow the prediction of the behavior of the joints for not experimentally tested parameter settings, within the operating domain of investigation. This aspect is particularly important in consideration of the process optimization of the manufacturing cycle since it allows the maximization of joint efficiency by limiting the energy consumption for treatment

Low-pressure plasma treatment of CFRP substrates for epoxy-adhesive bonding: an investigation of the effect of various process gases

This work reports a systematic and quantitative evaluation of the effects induced on the adhesive properties of carbon fiber reinforced polymer (CFRP) substrates by various vacuum cold-plasma treatments. In particular, surface activation of the CFRP substrates was performed using several combinations of exposure time, plasma power, and processing gas (air, O 2 , Ar and N 2 ). By comparing these plasma treatments with conventional techniques of abrasion and peel ply, it was possible to substantially increase the performance of the adhesively bonded joints made by overlapping the CFRP substrates with a structural epoxy resin. On each differently treated surface, measurements of roughness and of wettability were performed, allowing the evaluation of the increase in surface energy after the plasma treatment. XPS analyses allowed the identification of the chemical state of the substrates and showed an in-depth functionalization of the outer layer of the CFRP material. The experimental results show that an engineered plasma treatment of the CFRP substrates allows one to modify the surface morphology and both wetting and chemical activation properties of the treated surfaces, resulting in an increased mechanical shear strength of the joints

The Grizzly, November 16, 1984

College Acquires New Properties • Crime and Punishment: The New System • Officials Seek Return of Missing Air Masks • Editorial: Force Feeding the Student Body • Letters: Campus Sage Defends Lever Pullers; Group Claims Silent Coup • Study Abroad: A Student\u27s Trip to Scotland • Steady GPA Increase for Math and Poli Sci • Shorts: Pops Concert Scheduled; Shyness Workshop; Three Students Receive Award • Gridders Defeat Dickinson, 45-14 • X-Country Runner Earns Trip to Nationals • Swimmin\u27 women....and the Mermen • CPA Urges Students to Consider Optionshttps://digitalcommons.ursinus.edu/grizzlynews/1128/thumbnail.jp

Haptoglobin improves shock, lung injury, and survival in canine pneumonia

During the last half-century, numerous antiinflammatory agents were tested in dozens of clinical trials and have proven ineffective for treating septic shock. The observation in multiple studies that cell-free hemoglobin (CFH) levels are elevated during clinical sepsis and that the degree of increase correlates with higher mortality suggests an alternative approach. Human haptoglobin binds CFH with high affinity and, therefore, can potentially reduce iron availability and oxidative activity. CFH levels are elevated over approximately 24-48 hours in our antibiotic-treated canine model of S. aureus pneumonia that simulates the cardiovascular abnormalities of human septic shock. In this 96-hour model, resuscitative treatments, mechanical ventilation, sedation, and continuous care are translatable to management in human intensive care units. We found, in this S. aureus pneumonia model inducing septic shock, that commercial human haptoglobin concentrate infusions over 48-hours bind canine CFH, increase CFH clearance, and lower circulating iron. Over the 96-hour study, this treatment was associated with an improved metabolic profile (pH, lactate), less lung injury, reversal of shock, and increased survival. Haptoglobin binding compartmentalized CFH to the intravascular space. This observation, in combination with increasing CFHs clearance, reduced available iron as a potential source of bacterial nutrition while decreasing the ability for CFH and iron to cause extravascular oxidative tissue injury. In contrast, haptoglobin therapy had no measurable antiinflammatory effect on elevations in proinflammatory C-reactive protein and cytokine levels. Haptoglobin therapy enhances normal host defense mechanisms in contrast to previously studied antiinflammatory sepsis therapies, making it a biologically plausible novel approach to treat septic shock

Comparison of AA 2024 T3 friction stir welded and riveted overlap joints with the addition of a pressurization test

The aim of this work is to investigate the Friction Stir Welding (FSW) process applicability to a typical aeronautical joint: the union of the stiffeners to sheets constituting the fuselage. To do this analysis FSW parameters of flat overlapped sheets were first identified by monitoring the temperature reached using thermography. 1.3 mm thick AA 2024 T3 overlapped sheets were welded with success and the thermal effect due to the use of different welding parameters was compared with the results of mechanical tests and microstructural investigations. FSW joint mechanical properties were compared with those detected by performing tensile tests of joints made by riveting, showing absolutely comparable values. FSW identified parameters were used to make overlap joints between flat panels and stiffeners, so as to realize a typical structure of the aeronautical sector and to compare, by pressurization tests, the resistance of such panels with similar riveted. The innovative character of this research is represented by cyclic pressurization tests, conducted as indicated by the FAR (Federal Aviation Regulation) rules on a scale model. Thus it was possible to verify that the fatigue strength of welded panels is such as to overcome the acceptability limits fixed in the aeronautical field

AA8090 Al-Li alloy FSW parameters to minimize defectsand increase fatigue life

Increasing payload and fuel efficiency of aircrafts have become the major issues for the aerospace industry, which has increased the development of more advanced materials with highly specific properties. Low density aluminium lithium alloys are attractive to the aerospace industry since the structural weight reduction that they allow leads to an improvement of aircraft performance. Significant interest has been shown in the use of advanced welding techniques like Friction Stir Welding, particularly due to the design and manufacturing benefits that they afford over established mechanical joining methods. A significant benefit of FSW is the fact that it implies only a few process parameters to control: tool rotational speed, travel speed and applied normal load are easily controlled. This work presents an approach to optimise FSW process parameters which govern the tensile strength and the fatigue life of AA8090 Al-Li alloy through their effects on plastic flow in the nugget and in the thermo-mechanically affected zone (TMAZ), and through the thermal alteration in the heat affected zone (HAZ) of the weld. Therefore a close relationship exists between microstructure and fatigue performance, the typical plastic flow of a FSW joint and the occurrence of defect types, specific to FS process, can influence the fatigue behaviour of the joints