Sensitivity Analysis of GFRP Composite Drilling Parameters and Genetic Algorithm-Based Optimisation

In this article, a genetic algorithm (GA) is used for optimizing a metamodel of surface roughness (R_a ) in drilling glass-fibre reinforced plastic (GFRP) composites. A response surface methodology (RSM) based three levels (-1, 0, 1) design of experiments is used for developing the metamodel. Analysis of variance (ANOVA) is undertaken to determine the importance of each process parameter in the developed metamodel. Subsequently, after detailed metamodel adequacy checks, the insignificant terms are dropped to make the established metamodel more rigorous and make accurate predictions. A sensitivity analysis of the independent variables on the output response helps in determining the most influential parameters. It is observed that f is the most crucial parameter, followed by the t and D. The optimization results depict that the R_a increases as the f increases and a minor value of drill diameter is the most appropriate to attain minimum surface roughness. Finally, a robustness test of the predicted GA solution is carried out.

EXPERIMENTAL COMPARE OF THE MECHANICAL PROPERTIES OF PULTRUDED GLASS FIBRE REINFORCED PLASTIC BASED ON POLYESTER AND VINYLESTER RESIN

The main purpose of this study is an experimental investigation and comparison of the mechanical properties of pultruded glass fibre reinforced polymer composite based on polyester and vinylester resin. For this purpose, the specimens were cut from the walls of square tube pultruded profile along to the fibres direction. The mechanical properties of the pultruded composite such as ultimate tensile strength and ultimate bending strength, tensile modulus and flexural modulus were obtained. It was observed that using of vinyl ester resin in pultruded composite instead of polyester resin enhanced the ultimate tensile and flexural strength from ~13% to ~24% in dependence of composite specimen’s thickness.

Analysis of wave damping in pipeline having different pipe materials configuration under water hammer conditions

Hydraulic transient occurs whenever there is a sudden change in the flow velocity resulting in variation of pressure and flow in a water conductor system . Experiments have been conducted in a straight pipeline having material of Mild Steel (MS) and Glass Fibre Reinforced Plastic (GRP) pipelines and their combined configurations. From experiments, it has been observed that there is a smooth and strong damping of pressure waves in the pipeline system. Experimental results were compared with results obtained for classical water hammer equations solved in MATLAB and analyzed that there are several dissipative factors, other than fluid viscosity, responsible for strong damping of pressure wave amplitude. Further, an improvement in the governing equation of water hammer in a closed conduit was proposed by incorporating a different wave damping coefficient (a). The modified governing equations have been solved for each water hammer cycle using MATLAB. The numerical simulation results show that proposed approach gives better agreements between the experimental and computational results for all investigated cases.

Stability of GFRP composites with varied fractions of reinforcement exposed to ageing processes outdoors

The effects of outdoor ageing on various compositions of glass fibre reinforced plastic (GFRP) composites were studied. Changes in the interlaminar shear strength (ILSS) of hand-laid samples with 50–60 wt.% of fibre were determined by three-point bending and glass transition temperature (Tg) measurements. SEM analysis was carried out for exploring the mode of failure. The moisture ingress rate and extent were concentration-dependent at first, but became increasingly dependent on the fibre-matrix interfacial area. The ILSS initially fluctuated and then showed a decreasing trend with time, especially for the higher fibre concentrations. ILSS variations were zigzag initially and showed a lowering trend after the initial periods. Rate of lowering of ILSS was the highest for samples with the highest fraction reinforcement. Weight fraction reinforcement didn’t have any significant effect on the Tg variations. SEM fractograph revealed excessive fracture and fragmentation for the composite samples with the highest weight percentage reinforcement.

Reflection based Strain Sensing using Metamaterials

Resonator arrays of periodicially arranged electromagnetic sub-wavelength resonators show a strong frequency filter behaviour which can be controlled by the geometry, size and arrangement of the resonators. The use of several resonator arrays and their integration into a polymer matrix allows the realisation of metamaterials with a specific resonance behaviour. The resonance behaviour can be influenced by material and structural changes enabling a passive sensor function. The considered sensor approach based on metamaterials is investigated to enable structural health monitoring of lightweight structures. In the present case, a double-layer Jerusalem cross (JC) resonator array (RA) is integrated into a glass fibre reinforced plastic (GFRP) to analyse the change of the resonance behaviour under load (strain) using a reflection measurement. The CST (Computer Simulation Technology) Microwave Studio was used to model the resonator array for operation in the microwave frequency range between 15 GHz and 35 GHz as well as for the numerical analysis of the resonance behaviour under load. The numerical results were validated by a tensile test using a tensile test machine (type TIRATEST 28100, Tira GmbH) and by a reflection measurement using two standard gain horn antennas (type Standard Gain Horn Series 862, ARRA Inc) and a vector network analyser (type ZVA50, Rohde&Schwarz). The reflection measurement shows a reflection minimum at 28.6 GHz which moves to higher frequencies under load of the GFRP laminate. With the shift of the minimum, the quality factor decreases and the dip widens. The investigation shows that it is possible to provide a GFRP laminate with a specific electromagnetic behaviour by integrating resonator arrays. It is also shown that the specific electromagnetic behaviour can be influenced by structural changes and thus opens up the possibility of monitoring the condition of lightweight structures.