Browsing by Author "Rabiee, Ali"
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Item Open Access Effect of multi stitched locations on high speed crushing of composite tubular structures(Elsevier, 2016-06-20) Rabiee, Ali; Ghasemnejad, HessammaddinThe present paper experimentally investigates progressive energy absorption of fibre-reinforced polymer (FRP) composite tubular structures under high speed loading conditions. Various multi stitched locations are studied to find a correlation between single and multi-locations of stitches and energy absorption capabilities of composite absorbers. The through-thickness reinforcements are applied into locations of 10 mm, 20 mm, 30 mm, 10–20 m, 10–30 mm, 20–30 mm, 10–20–30 mm and 10–15–20–25–30–35 mm from top of the tubes. It is shown that multi-stitched location can cause several increase of crushing load and consequently increase of energy absorption of composite tube absorbers. The idea would be expanded to other designs which are followed by increase of stitched locations and reduction of the distance between stitches to improve the mean force with a smooth and progressive pattern of crushing load.Item Open Access Effect of stitching pattern on composite tubular structures subjected to quasi-static crushing(2016-10-31) Rabiee, Ali; Ghasemnejad, HessammaddinExtensive experimental investigation on the effect of stitching pattern on tubular composite structures was conducted. The effect of stitching reinforcement through thickness on using glass flux yarn on energy absorption of fiber-reinforced polymer (FRP) was investigated under high speed loading conditions at axial loading. Keeping the mass of the structure at 125 grams and applying different pattern of stitching at various locations in theory enables better energy absorption, and also enables the control over the behaviour of force-crush distance curve. The study consists of simple non-stitch absorber comparison with single and multi-location stitching behaviour and its effect on energy absorption capabilities. The locations of reinforcements are 10 mm, 20 mm, 30 mm, 10-20 mm, 10-30 mm, 20-30 mm, 10-20-30 mm and 10-15-20-25-30-35 mm from the top of the specimen. The effect of through the thickness reinforcements has shown increase in energy absorption capabilities and crushing load. The significance of this is that as the stitching locations are closer, the crushing load increases and consequently energy absorption capabilities are also increased. The implementation of this idea would improve the mean force by applying stitching and controlling the behaviour of force-crush distance curve.Item Open Access Finite element modelling approach for progressive crushing of composite tubular absorbers in LS-DYNA: review and findings(MDPI, 2021-12-29) Rabiee, Ali; Ghasemnejad, HessamRobust finite element models are utilised for their ability to predict simple to complex mechanical behaviour under certain conditions at a very low cost compared to experimental studies, as this reduces the need for physical prototypes while allowing for the optimisation of components. In this paper, various parameters in finite element techniques were reviewed to simulate the crushing behaviour of glass/epoxy tubes with different material models, mesh sizes, failure trigger mechanisms, element formulation, contact definitions, single and various numbers of shells and delamination modelling. Six different modelling approaches, namely, a single-layer approach and a multi-layer approach, were employed with 2, 3, 4, 6, and 12 shells. In experimental studies, 12 plies were used to fabricate a 3 mm wall thickness GFRP specimen, and the numerical results were compared with experimental data. This was achieved by carefully calibrating the values of certain parameters used in defining the above parameters to predict the behaviour and energy absorption response of the finite element model against initial failure peak load (stiffness) and the mean crushing force. In each case, the results were compared with each other, including experimental and computational costs. The decision was made from an engineering point of view, which means compromising accuracy for computational efficiency. The aim is to develop an FEM that can predict energy absorption capability with a higher level of accuracy, around 5% error, than the experimental studies.Item Open Access Improvement of specific energy absorption of composite tubular absorbers using various stitching pattern designs(Springer, 2020-11-26) Rabiee, Ali; Ghasemnejad, HessamIn this paper, various patterns of multi-stitched locations were studied experimentally and numerically to improve the specific energy absorption (SEA) in composite tubular absorbers. In this regard, stitching patterns with a horizontal distance of 3 mm, 6 mm, 9 mm and 18 mm in straight and zig-zag designs were investigated to justify their effect on mean crushing force and energy absorption capability. A multi-shell configuration finite element model is also developed based on energy-based contact definitions, which considers the delamination in Mode-I and stitching pattern design to accurately predict the energy absorption capability and axial crushing behaviour of composite crash absorbers, At stitched locations, the critical normal surface separation was utilised concerning experimental data to improve delamination resistance. The multi-stitching rows of 10–15-20–25-30–35 mm with 3 mm horizontal and 2.5 mm vertical distances between each stitched point can increase the specific energy absorption up to 32% in comparison with non-stitched specimens. The developed numerical model for multi-layered composites absorbers in comparison with the existing methods is efficient in terms of accuracy with less than 5% error in comparison with experimental data.Item Open Access Laminate tailoring of composite tubular structures to improve crashworthiness design at off-axis loading(Scientific Research Publishing, 2018-07-10) Rabiee, Ali; Ghasemnejad, HessamThis paper presents experimental and numerical investigation on the parameters effecting energy absorption capability of composite tubular structures at oblique loading to improve crashworthiness performance. Various inclined angles of 5˚, 10˚, 20˚ and 30˚ were selected for the study of off-axis loading. The results indicate that by increasing the lateral inclination angle the mean crushing force and also energy absorption capability of all tested sections decreased. From design perspective, it is necessary to investigate the parameters effecting this phenomenon. The off-axis loading effect that causes significant reduction in energy absorption was investigated and the effected parameters were improved to increase energy absorption capability. To establish this study, 10˚ off-axis loading was chosen to illustrate the obtained improvement in energy absorption capability. Five cases were studied with combinations of ply-orientation and flat trimming with 45˚ chamfer. This method was applied to the integrated 10˚ off-axis loading and the final results showed significant improvement in energy absorption capability of composite absorbers. Finite element model (FEM) was developed to simulate the crushing process of axial and off-axis composite section in LS-DYNA and the results were in good agreement with the experimental data.Item Open Access Lightweight design of multi-stitched composite crash absorbers to improve specific energy absorption capability under quasi-static and impact loading(2018-05) Rabiee, Ali; Ghasemnejad, HessamA comprehensive numerical and experimental study was performed to investigate the energy absorbing capabilities of glass/epoxy and carbon/epoxy members that could serve as stanchions in the subfloor structure of aircraft or rotorcraft. Circular cross sections with chamfered-ends failure trigger mechanism were investigated under axial and off-axis loading conditions. The optimal configuration that resulted in the highest possible specific energy absorption (SEA) was identified, which was at axial loading. The parameters in off-axis loading conditions that affected energy absorption capability were identified. Several cases were experimentally studied to cancel off-axis (oblique) loading effect. To increase interlaminar fracture toughness, stitching through the thickness was considered. Single, multi and pattern-stitching were studied to increase energy absorption capability of GFRP composite sections. The failure mechanisms, crushing process and force-displacement curve diagram of each case was studied to establish the effect of stitching on energy absorption capability. A correlation between stitching location and localised and global increase of energy absorption was established. It was identified, that the closer the stitching locations are, the higher the localised peak load becomes, and it influences the Mode-I crack propagation (main central crack) resistance, bending of fronds and friction, consequently, pattern-stitching resulted in a 15% increase in specific energy absorption capability (SEA) under quasi-static loading. Similarly, this stitching pattern resulted in a 14% increase in SEA using CFRP sections. Under impact loading, it was identified that pattern-stitching through the thickness resulted into 17% and 18% increase in SEA using GFRP and CFRP sections, respectively. Finite element models were also developed to simulate the crushing behaviour of the CFRP and GFRP sections observed experimentally under axial, off-axis, quasi-static and impact loading conditions. A multi-layer modelling methodology was developed by determining the most effective element size, number of shells, formulation, contact definitions, delamination interface, material model, friction and trigger mechanism. This approach captured the failure process, predicted the SEA and sustained crush load quite accurately within 5% error. Stitching through the thickness was modelled using an energy-based contact card to implement stitched and non-stitched Mode-I and Mode-II energy release rate parameters. This method accurately predicted stitched composite sections with 3% error compared with experimental data. Such modelling could thus support the future design of aircraft stitched and non-stitched stanchions within reasonable computer efficiency and accuracy.Item Open Access Lightweight design to improve crushing behaviour of multi-stitched composite tubular structures under impact loading(Elsevier, 2018-11-19) Rabiee, Ali; Ghasemnejad, HessamThis paper presents experimental and numerical studies on the effect of multi-stitching pattern on the energy absorption capability of composite tubular structures under impact loading. A new multi-stitching pattern was developed to study the increase of specific energy absorption capabilities in GFRP and CFRP crash absorbers. The stitching pattern on both specimens showed a significant increase in energy absorption capability under impact loading. According to our results, the specific energy absorption of GFRP and CFRP composite tubes are 17% and 18% higher than non-stitched specimens respectively. A multi-shell finite element model was constructed to predict the axial crushing behaviour and energy absorption capability of composite structures under impact loading. The method is based on an energy-based contact card modelling technique in the stitched and non-stitched area, and the initiation of main central crack growth occurs when the critical separation (PARAM function) is attained, and this represents the functionality of the stitched area during an impact event. The developed numerical approach is efficient in terms of accuracy and simplicity in comparison with the existing methods for multi-layered composites structures.Item Open Access Numerical model development to predict the behaviour of infant/neonate crash dummy restrained inside of an incubator under deceleration(Springer, 2021-07-31) Rabiee, Ali; Ghasemnejad, Hessam; Hitchins, N.; Watson, J.; Roberts, J.; Khoory, M.In this paper, advanced finite element (FE) methods are developed to investigate the effect of deceleration on the crash dummy test complied with British Standard Engineering (BS EN 1789). These techniques, which are related to material modelling, joints and contacts, offer an advanced numerical model representing an infant incubator with all complex boundary conditions and design contents. It is shown that the response of an infant incubator is a function of the ratchet straps, the tension on the belts, the belt type and the distance of the belts from the edges of the incubator, which can significantly affect the experienced acceleration, by the infant. The validation process is performed against experimental studies and various case parameters such as crash dummy mass and negative acceleration impulse are discussed in detail. The developed numerical model is capable to predict the behaviour of the crash dummy and the incubator in terms of acceleration, trajectory and kinematics by less than 8% error.Item Open Access Progressive Crushing of Polymer Matrix Composite Tubular Structures: Review(Scientific Research Publishing, 2017-01) Rabiee, Ali; Ghasemnejad, HessammaddinThe present paper reviews crushing process of fibre-reinforced polymer (FRPs) composites tubular structures. Working with anisotropic material requires consideration of specific parameter definition in order to tailor a well-engineered composite structure. These parameters include geometry design, strain rate sensitivity, material properties, laminate design, interlaminar fracture toughness and off-axis loading conditions which are reviewed in this paper to create a comprehensive data base for researchers, engineers and scientists in the field. Each of these parameters influences the structural integrity and progressive crushing behaviour. In this extensive review each of these parameters is introduced, explained and evaluated. Construction of a well-engineered composite structure and triggering mechanism to strain rate sensitivity and testing conditions followed by failure mechanisms are extensively reviewed. Furthermore, this paper has mainly focused on experimental analysis that has been carried out on different types of FRP composites in the past two decades.