Characterisation of Glass Fibre Polypropylene and GFPP based Fibre Metal Laminates at high strain rates

Fibre reinforced polymers (FRP) are finding increasing use in structures subjected to high rate loading such as blast or impact. Proper design of such structures requires thorough characterisation of the material behaviour over a range of loading rates from quasi-static to impact. This thesis investigated the quasi-static and impact response of Glass Fibre Polypropylene (GFPP) in compression, bending and delamination. The bending and delamination response of Fibre Metal Laminates (FMLs) based on GFPP and aluminium was also investigated at quasi-static and impact rates. High strain rate (5x10^2 to 10^3 /s) compression tests were conducted on GFPP using a compressive Split Hopkinson Pressure Bar (SHPB) and a Direct Impact Hopkinson Pressure Bar (DIHPB), in the through-thickness and in-plane directions. In both loading directions, the peak stress of GFPP increased linearly with the logarithm of strain rate. For in-plane loading, the failure modes were dominated by localised fibre buckling and kink bands, leading to delamination. The through thickness loading produced macroscopic shear and spreading failure modes. However, both of these failure modes are linked to in-ply fibre failures, due to through thickness compression causing transverse tensile strain. Previous studies of similar materials have not explicitly stated the link between through thickness compression and fibre failure associated with transverse tensile strain. A novel test rig was developed for Three Point bend testing at impact rates. The specimen was supported at the outer points on a rigid impacter and accelerated towards a single output Hopkinson Pressure Bar (HPB), which impacted the specimen at its midspan. Previous impact bend test rigs based on HPBs were limited to testing specimens with deflections to failure up to approximately 1mm, whereas the rig implemented herein measured deflections up to approximately 10 mm. This configuration permits the output HPB to be chosen purely on the magnitude of the expected impact force, which resulted in superior force resolution to configurations used in other studies. The HPB Impact Bend rig was used to test GFPP and aluminium-GFPP FML specimens, at impact velocities ranging from 5 to 12 m/s. The flexural strength of GFPP increased with strain rate, while the flexural response of the FML specimens was relatively insensitive to strain rate. v Several candidate delamination test geometries were investigated at quasi-static displacement rates (1 mm/min), and the Single Leg Bend (SLB) test was identified as suitable for adaptation to higher rate testing. Single Leg Bend delamination tests of both GFPP and FML specimens were performed using the HPB Impact Bend rig, at impact velocities of 6 to 8 m=s. The shape of the force displacement response for the high rate testswas markedly different from the quasi-static tests, for both the GFPP and FML specimens. Finite element (FE) simulation of the quasi-static and impact rate SLB tests on GFPP indicated that the difference was probably due to the interaction of flexural vibrations and stress waves in the specimen and the impacter cross member. The experimental results and FE analysis suggest that the delamination fracture toughness of GFPP decreases slightly as strain rate increases. High rate delamination tests on FML specimens resulted in unstable crack growth

Shear Stress Distribution and Hemolysis Measurements in a Centrifugal Blood Pump

The use of computational fluid dynamics (CFO) to predict red blood cell trauma (hemolysis) in blood pumps based on their exposure to turbulent stresses has increased in recent years. The U.S. Food and Drug Administration (FDA) has initiated a project to determine the fidelity with which modern CFO can accurately predict hemolysis in such devices. The project involves the collection of experimental data against which externally-conducted CFO simulations may be compared. Because the data will be used to judge the ability of CFO to predict hemolysis, the pump was designed to cause more turbulence and blood damage than would be typical of an approved clinical device. In support of this effort, a shaft-driven centrifugal blood pump was constructed for use in both quantitative flow visualization analysis and in blood-damage experiments. The hydraulic performance of the pump was measured to determine the degree to which it represented a typical blood pump. Particle image velocimetry (PIV) was used to measure planar velocity fields in three different regions of the pump including the blade passage, impeller rear-gap, and cutwater region. For all PIV experiments, the pump delivered volumetric flow rates of 0.6, 3.0, and 6.0 liters per minute (LPM), each at a constant shaft speed of 2800 RPM. Statistical analysis was performed on each PIV data set in order to determine the time-averaged velocity fields as well as to resolve turbulent quantities of interest to the prediction of hemolysis (namely the Reynolds shear stresses). Additionally, the pump was operated using bovine blood as the working fluid in order to measure the hemolysis caused at the same operating points measured during PIV experiments. Further experiments were conducted to determine the contribution of the pump\u27s shaft-seal interface to the total measured hemolysis. The pump\u27s hydrodynamic performance was measured to be a close match to that of a typical clinical blood pump. PIV analysis revealed that the velocity and shear stress fields within the pump were dependent on its operating point, and can thus serve as benchmarking data against which to compare CFO analyses. Finally, the pump was confirmed to produce measurable hemolysis. The contribution of a polyurethane shaft seal to the measured hemolysis was significant (39%-62% of the total VAD hemolysis), but this contribution was small (7%-9% of the total VAD hemolysis) when a Teflon seal was used

Numerical and experimental investigation of deformation and strength properties of lithophysae -rich tuff and analog materials

Portions of the high-level nuclear waste repository in Yucca Mountain will be located in lithophysae-rich tuff formations. Understanding the mechanical properties of the lithophysae-rich tuff, including deformation modulus, deformation ratio and compressive strength, is an important issue for design and the performance of the repository tunnels. These properties are expected to be significantly affected by lithophysal porosity; Two different research directions are implemented in this dissertation. First, uniaxial compression testing is simulated using finite difference technique on models containing circular holes in order to investigate the effect of porosity on deformation parameters. Numerical results are compared with biaxial test results of urethane specimens containing circular tubes to verify the numerical analysis results; Second, an experimental program that consists of uniaxial compression tests on analog models and tuff is conducted. Two different configurations are implemented to model porosity using gypsum plaster as an analog material. In the first configuration analog models containing uniformly and randomly distributed open ended cylindrical tubes are produced. In the second configuration spherical cavities are introduced into the analog models. Both models are tested under uniaxial compression and their deformation moduli and compressive strength are compared with lithophysae-rich tuff specimens that are obtained from outcrops of lithophysal tuff units; Numerical modeling and testing are combined to assess that the deformation modulus of tuff where the porosity has a vital effect on mechanical behavior of the rock. Both numerical analysis and uniaxial testing on analog materials show that in deformation modulus exponentially decrease with increasing porosity. The deformation moduli and compressive strength of gypsum plaster specimens containing open ended cylindrical tubes are slightly lower than those containing spherical cavities due to confinement effects; The deformation moduli and compressive strengths of the tuff specimens fall between the values determined for the plaster specimens with two different porosity configuration. Distribution of data for both analog and tuff specimens is very similar at low porosities. At higher porosities, a greater decrease in deformation modulus is observed in tuff due to larger and nonspherical cavities indicating that shape of the cavities is a factor affecting the modulus

The 20th Aerospace Mechanisms Symposium

Numerous topics related to aerospace mechanisms were discussed. Deployable structures, electromagnetic devices, tribology, hydraulic actuators, positioning mechanisms, electric motors, communication satellite instruments, redundancy, lubricants, bearings, space stations, rotating joints, and teleoperators are among the topics covered

Eleventh International Conference on the Bearing Capacity of Roads, Railways and Airfields

Innovations in Road, Railway and Airfield Bearing Capacity – Volume 2 comprises the second part of contributions to the 11th International Conference on Bearing Capacity of Roads, Railways and Airfields (2022). In anticipation of the event, it unveils state-of-the-art information and research on the latest policies, traffic loading measurements, in-situ measurements and condition surveys, functional testing, deflection measurement evaluation, structural performance prediction for pavements and tracks, new construction and rehabilitation design systems, frost affected areas, drainage and environmental effects, reinforcement, traditional and recycled materials, full scale testing and on case histories of road, railways and airfields. This edited work is intended for a global audience of road, railway and airfield engineers, researchers and consultants, as well as building and maintenance companies looking to further upgrade their practices in the field

Cumulative index to NASA Tech Briefs, 1963-1967

Cumulative index to NASA survey on technology utilization of aerospace research outpu

Cumulative Index to NASA Tech Briefs, 1963 - 1966

Cumulative index of NASA Tech Briefs dealing with electrical and electronic, physical science and energy sources, materials and chemistry, life science, and mechanical innovation

Measurement of low concentration and nano quantity hydrogen sulfide by carbon nanotube

Traditionally, hydrogen sulfide (H2S) has been regarded as toxic. It can affect the various human systems and even cause death. However, research in the 1990’s has shown that H2S can be endogenously generated by many cells and tissues in mammalian bodies, and that H2S also may play physiological roles such as those of neuromodulator and vasorelaxant in the biological system. As such, the precise measurement of the amount of H2S in a mammalian body has generated researchers’ strong interest. The ultimate goal of such a measurement should be conducted in-vivo and in real time.The existing methods for H2S measurement require both a large quantity of tissue samples and a complex procedure, so they are not highly practicable for the purpose of achieving the aforementioned goal. In this dissertation, a new method that uses carbon nanotube as an absorbent or transducer and laser-based microscopy techniques (Raman and confocal laser scanning microscopy) as signal excitation and acquisition is proposed and developed. Experimental studies are described of using this new method for analysis of both distilled water samples and serum samples in which a group of proteins are present. The study concludes that the new method (1) can measure H2S in water solutions down to a low level of concentration of 10 µM, (2) can measure H2S in sera down to a low concentration of approximately 20 µM), and (3) has a high feasibility for being used in the clinical context. Regarding (3), this is confirmed by presenting a control system that allows the laser microscopy to track carbon nanotube in a solution that has Brownian motion.While not having reached the ultimate goal as mentioned above, this work advances the state-of-the-art of the measurement of low concentration and nano-quantity of H2S in water and serum samples, in particular providing a promise toward a real-time and in-vivo H2S measurement

Design of eco-sustainable bituminous mixtures for road pavements

In the civil engineering sector and in particular in road construction, attention is increasingly being focused on the need for "sustainable development", which reflects the growing trend, on the one hand, to reduce the amount of materials taken to landfills and, on the other hand, to conserve and reuse non-renewable resources (suitably treated) instead of raw materials that should be preserved in nature. The aim of this thesis was to enhance the conservation of local natural resources by reusing secondary raw materials such as Reclaimed Asphalt Pavement (RAP), Jet grouting waste (JW) and plastic waste (PW) in the construction of sustainable infrastructures. The different sizes of each material have led to investigate the mechanical behaviour of different scales of the mixture; in particular, laboratory tests have focused on the rheological behaviour of bituminous mastics when JW and PW are adopted as filler, while static and dynamic tests focused on hot and cold bituminous mixtures when JW and RAP are used as aggregates. With the aim to create a complete procedure supporting the decision makers in the comparative analysis of the designed bituminous mixtures as base layer of a flexible pavement, taking into account not only the mechanical variables linked to the performance of the mixtures, but also in terms of environmental sustainability, an LCA was developed. Finally, to identify the most appropriate bituminous mixture solution, a sensitivity analysis was implemented