Browsing by Author "Danezis, Anastasios"
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Item Open Access Data supporting: 'In-process nip point temperature estimation in automated tape placement based on analytical solution and remote thermal measurements'(Cranfield University, 2022-08-31 15:50) Danezis, Anastasios; Skordos, Alex; Williams, DavidFE and 1D predictions comparison: nip point temperature estimates by the analytical scheme and FE model.Inverse solution data: tool surface temperatures before and after the addition of Gaussian noise, irradiance profile applied in FE model and its approximations using the inverse solution. Metallic and insulating tool material.Example application- power variation: contains the data of the virtual experiment generated by the FE model, and analytical scheme estimates for different scenarios.Item Open Access Data supporting: One-dimensional approximation of heat transfer in flashlamp-assisted automated tape placement(Cranfield University, 2023-02-20 11:37) Danezis, Anastasios; Skordos, Alex; Williams, DavidComparison 1D_2D: predictions of 1D and 2D methodologies for a wide range of processing rates, deposited material thickness and pulsing conditions. Data of computational effort for equivalent predictions are also included.Item Open Access Heat transfer modelling of flashlamp heating for automated tape placement of thermoplastic composites(Cranfield University, 2021-03-22 15:37) Danezis, Anastasios; Williams, David; Edwards, Michael; Skordos, AlexHeat transfer model validation: contains the experimental temperature data captured during the manufacture of AS4/PEEK composites and the corresponding model predictions.Irradiance profiles: contains the optical model predictions for the configuration used in the study and the data after the application of smoothing algorithm.Thermal model 2D geo: the geometry of the heat transfer model.Bulk profiles: contains the bulk profiles as predicted by the thermal model for the 25, 50, 100 Hz pulsed cases and continuous operation.Item Open Access Heat transfer modelling of flashlamp heating for automated tape placement of thermoplastic composites(Elsevier, 2021-03-13) Danezis, Anastasios; Williams, David; Edwards, Michael; Skordos, Alexandros A.Flashlamp systems introduce pulsed and broadband heating to automated tape placement (ATP) offering greater control and optimisation potential. A thorough understanding of the role of operation parameters on the process is necessary to unlock these capabilities. A 2D finite element model of the heat conduction, able to analyse the temperature field evolution in the time scales of short high-energy pulses was developed and combined with ray tracing analysis in this work. The model was validated against experimental data from ATP trials of AS4/PEEK composites. Parametric studies showed that pulse duration and frequency influence significantly both the surface and bulk temperature profiles. Longer pulses lead to higher irradiation temperatures, whilst the profiles converge to the behaviour of a continuous source of equivalent power at high frequency. The versatility of flashlamp heating enhances the processing envelope through expanding the feasible combinations of maximum temperature and depth of penetration achievable in ATP processingItem Open Access Heat transfer modelling, optimisation and monitoring of flashlamp- assisted automated tape placement.(Cranfield University, 2023-06) Danezis, Anastasios; Skordos, Alexandros A.; Williams, DavidThis study aims to develop tools for the design, optimisation and control of automated tape placement (ATP) that integrates flashlamp heating. A thermo-optical simulation of ATP is developed, combining a 2D finite element model of the heat conduction with 3D ray tracing analysis. The methodology is validated against measurements acquired during ATP trials of AS4 carbon/PEEK composites, presenting deviations up to 20°C. Flashlamp operation at low frequency and long pulses (25 Hz /4.75 ms) results in up to 150°C higher irradiation temperatures and increased thermal penetration depth, 100 over 50 μm, compared to high frequency and short pulses (100 Hz/1.1 ms) or continuous operation. Consolidation temperatures under the roller are identical for pulsing scenarios of equivalent average power, including continuous operation. To increase computational efficiency, an 1D simulation of ATP is put forward comprising distinct models representing the tow, deposited material, and consolidated stack with transfer of temperature information to ensure field continuity. The 1D solution requires only 1-2% of the computational effort of the 2D model with a minor trade-off in accuracy, up to 14°C. Based on the efficient 1D solution, an optimisation scheme of ATP is developed by integrating models of material degradation, interfacial bonding and a Genetic Algorithm. The optimisation scheme identifies the Pareto front of the multi-objective problem accurately in 25% of the computational effort required for an exhaustive search. Strong trade-offs exist between bonding, thermal degradation and productivity, limiting the average bonding value in the stack to 0.35 before matrix degradation exceeds the 1% threshold typically set for aerospace applications. A monitoring strategy for ATP of thermoplastic prepregs is proposed combining 1D analytical solutions and temperature data acquired on the tool side of the deposited material, allowing estimation of nip point temperatures in real time. The method integrates an inverse solution to determine the heater power input from temperature data and enhance the nip point estimation accuracy. The monitoring scheme presents good accuracy for a wide range of velocities, substrate thickness and tooling materials, with an average error of 15°C even in the presence of significant measurement noise.Item Open Access In-process nip point temperature estimation in automated tape placement based on analytical solution and remote thermal measurements(SAGE, 2022-08-22) Danezis, Anastasios; Williams, David; Skordos, Alexandros A.The optimisation and control of automated tape placement (ATP) requires fast analysis tools able to utilise process data for predictions and monitoring. In this study, a strategy for in-process estimation of nip point temperatures is proposed. The method is based on a combination of two one-dimensional analytical solutions of heat transfer in ATP using temperature data measured on the tool surface, combined with an inverse solution for the estimation of power delivered by the heating device on the composite surface. The performance of the method is examined against a validated finite element model. Approximations of nip point temperature show good correlation for different tool materials, with an average error of 15°C and a maximum of 50°C which is satisfactory for the processing of high-temperature thermoplastic materials. The analytical scheme offers real-time estimations of the nip point temperature with the potential to be used for process control of ATP.Item Open Access One-dimensional approximation of heat transfer in flashlamp-assisted automated tape placement(Sage, 2023-02-17) Danezis, Anastasios; Williams, David; Skordos, Alexandros A.A computationally efficient heat transfer simulation of flashlamp-assisted automated tape placement (ATP) is put forward in this work. The simulation combines distinct 1D finite element models representing the tow, the deposited material, and the resulting stack with appropriate transfer of temperature information to ensure field continuity. Direct comparison against a validated 2D model of ATP shows good agreement in the irradiation region, underneath and beyond the roller vicinity with errors up to 14°C. The combined solution of 1D models requires only 1-2% of the computational effort needed for an equivalent 2D analysis without compromising results resolution, whilst it is better suited for providing the full material temperature history throughout consecutive processing cycles. The accuracy and fast computation render this method appealing for studies which require an iterative execution of the model in a practical timeframe such as in optimisation schemes, inverse solutions, training of surrogate models and stochastic simulation.