Numerical analysis of a sling support arrangement for grp composite pressure vessels

A flexible sling support arrangement for horizontal glass reinforced plastic pressure vessels is examined using advanced finite element methods. A mathematical model is produced employing a suitable analysis capable of representing the non-linear behaviour of a sling supported GRP vessel. This system is used to examine the phenomena occurring at the interface between the vessel and the supporting belt. Each component is initially considered some distance apart and then brought together using three-dimensional contact surfaces. External loads are thereafter applied to the combined model. Although several numerical difficulties arise due to the difference in flexibility between the vessel shell and the sling support, these are overcome and the resulting vessel strains and contact interface pressures show good agreement with experimental work. The magnitudes of the strains at the location of the saddle horn are significantly reduced. Results of a parameter study are also presented which show the effect of the sling position together with the influence of the wrap-round angle and a number of recommendations are made with respect to design

The assessment of complex learning outcomes

The Engineering Professors' Council (EPC) produced an output standard in 2000 containing a setof 26 generic statements of what an engineering graduate should have an ability to tackle. In addition, Higher Education (HE) is concerned with the promotion of complex or advanced understanding of subject matter. This leads to complex learning outcomes, which need to be adequately assessed. Changing demands mean changing assessment practices. While good practice is being used in many cases, there is a need to ensure assessment stimulates complex learning. The article seeks to address these issues

Non destructive examination of composite structures using dielectric examination

Dielectric measurements are widely used in the laboratory to probe the dynamics of molecules, particularly the dynamics of polymer molecules. The dielectric technique exploits the fact that many molecules, although electrically neutral posses an asymmetric distribution of charges which can be approximated to an electric dipole. The (usually thermal) motion of the molecule can be detected by the interaction of this dipole with a time varying electric field. The great advantage of the technique is that no transducers or sensors are required; the direct application of an electric field produces a directly measurable electric response over a frequency range of MHz to GHz. This paper discusses the practical application of dielectric measurements to composite structures and the information that can be obtained on the state of the polymer in polymer composite matrix materials

Impact characterisation of doubly curved composite structure

Under repeated impact composite domes subjected 6 J energy, changes locally with increasing drop height. The action of the dynamic load generates reactions at the support and bending moments at points on the surface of the composite. The peak loads were noted to increase and stabilise about some mean value; and the 150mm diameter shell was more damage tolerant compared to the 200 mm diameter one

An experimental study of damage accumulation in balanced CFRP laminates due to repeated impact

The behaviour of balanced laminates (symmetric, antisymmetric and asymmetric) under repeated low energy hits of a 12.1 mm hemispheric impactor was evaluated. The resistance to the impulsive force was found to be influenced by the stacking sequence and the crack path through the laminate. The symmetric plate with different ply directions proved to have best resistance to impact. The rate of damage progression in the event was characterised by an equation from the energy profile that correlates the propagation energy and time. This was differentiated to give the rate of damage evolution. A comparison of the bending stiffness obtained from the force-displacement plot of the first impact, revealed that the symmetric composite had the highest stiffness. Noted at perforation were fibre breakage and matrix cracking

A study of repeated impact loading on a symmetrical carbon fibre laminate

The behaviour of a symmetric laminate under repeated low energy hits of a 12.1mm hemispheric impactor was evaluated. The laminate was able to endure 20 collisions with the striker before perforation. The rate of damage progression was characterised by an equation from the energy profile that correlates the propagation energy and time. The function was represented by a sixth order polynomial. This was differentiated to give the rate of damage evolution. The contact time related to theimpact events with the same degree of polynomial. At perforation fibre breakage and matrix cracking were observed

A parametric study of alternative support systems for cylindrical GRP storage vessels

Paper presenting a parametric study of alternative support systems for cylindrical GRP storage vessels

The chemical compatibility of thermoplastic hose used in umbilicals

The effects of solvents and temperature on thermoplastic hose for umbilical service are reported in this paper. Accelerated ageing tests were undertaken and analysed by gravimetric, mechanical and calorimetric measurements. Water and methanol were found to cause physical degradation of the polymer, mainly at high temperatures, whereas xylene caused chemical degradation, which increased with increasing temperature. The activation energy for the alpha-process within polyethylene (PE) was found to be 96.3 kJ mol(-1) for un-aged PE and increased to 106.2 kJ moll after 64 days of ageing in water at 100degreesC. The changes in activation energy will be used to make a life-time prediction of umbilical line

Tensile testing of cellulose based natural fibers for structural composite applications

A series of tensile tests were conducted on a Lloyd LRX tensile testing machine for numerous natural fibers deemed potential candidates for development in composite applications. The tensile tests were conducted on the fibers jute, kenaf, flax, abaca, sisal, hemp, and coir for samples exposed to moisture conditions of (1) room temperature and humidity, (2) 65% moisture content, (3) 90% moisture content, and (4) soaked fiber. These seven fibers were then tested for the four conditions and the mechanical properties of tensile strength, tensile strain to failure, and Young's modulus were calculated for the results. These results were then compared and verified with those from the literature, with some of the fibers showing distinctly promising potential. Additionally, a study on the effect of alkalization using 3% NaOH solution was carried out on flax, kenaf, abaca, and sisal to observe impact that this common fiber pre-treatment process has on fiber mechanical properties. The result of the investigation indicated that over treatment of natural fibers using NaOH could have a negative effect on the base fiber properties. It is consequently apparent that a treatment time of less than 10 min is sufficient to remove hemicelluloses and to give the optimum effect

Cosmological constraints on unparticle dark matter

In unparticle dark matter (unmatter) models the equation of state of the unmatter is given by $p=\rho/(2d_U+1)$, where $d_U$ is the scaling factor. Unmatter with such equations of state would have a significant impact on the expansion history of the universe. Using type Ia supernovae (SNIa), the baryon acoustic oscillation (BAO) measurements and the shift parameter of the cosmic microwave background (CMB) to place constraints on such unmatter models we find that if only the SNIa data is used the constraints are weak. However, with the BAO and CMB shift parameter data added strong constraints can be obtained. For the $\Lambda$UDM model, in which unmatter is the sole dark matter, we find that $d_U > 60$ at 95% C.L. For comparison, in most unparticle physics models it is assumed $d_U<2$. For the $\Lambda$CUDM model, in which unmatter co-exists with cold dark matter, we found that the unmatter can at most make up a few percent of the total cosmic density if $d_U<10$, thus it can not be the major component of dark matter.Comment: Replaced with revised version. BAO data is added to make a tighter constraint. Version accepted for publication on Euro.Phys.J.