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Paul Compston - One of the best experts on this subject based on the ideXlab platform.
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Investigation of the effects of heating bias and placement head angle on the short Beam Strength of CF/PEEK laminates manufactured in a laser tape placement process
2017Co-Authors: C. Stokes-griffin, Paul Compston, A. Kollmannsberger, Klaus DrechslerAbstract:This paper investigates the effects of heating bias and placement head angle on the short Beam Strength (SBS) of unidirectional CF/PEEK laminates manufactured in a laser tape placement process. Placement trials were performed with constant laser power at 400 mm/s. The effect of heating bias was studied by changing the bias angle of the laser by +-0.5 degrees from the default position where the surface temperature on the tape and substrate are equal. The angle of the placement head relative to the tooling was also varied by +-6.0 degrees from the default position. The process was instrumented with a long wave infra-red thermal camera. The SBS of the samples was determined following the ASTM D 2344 standard. Increasing the laser bias +0.5 degrees towards the tape had no effect on the SBS, however increasing the bias towards the substrate by -0.5 degrees resulted in a 26% decrease in SBS. This was attributed to the substrate acting as a heat sink, combined with insufficient heating of the tape. Decreasing the angle between the placement head and the tooling by 6.0 degrees lead to a 10% decrease in SBS. This was attributed to the increased angle of incidence, leading to decreased laser absorptance and therefore lower bond interface temperatures. Increasing the angle of the placement head by 6.0 degrees revealed no significant difference in Strength.
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the effect of processing temperature and placement rate on the short Beam Strength of carbon fibre peek manufactured using a laser tape placement process
Composites Part A-applied Science and Manufacturing, 2015Co-Authors: Christopher Stokesgriffin, Paul CompstonAbstract:Abstract The ability of a modern near infra-red laser tape placement system to produce high-quality laminates is investigated by performing short Beam Strength tests on samples manufactured at different process temperatures from 400 °C to 600 °C at placement rates of 100 mm/s and 400 mm/s. The temperature history in tape placement is highly dynamic and the correlation between the process control temperature, laser power and the consolidation temperature is not well understood. The complete temperature history was therefore estimated with a previously developed optical-thermal model and validated using long wave infra-red imaging. Short Beam Strengths equivalent to conventional manufacturing methods were found for placement rates of 400 mm/s. Failure modes of the samples were elucidated by scanning electron microscopy of the fracture surfaces. Signs of degradation were observed on samples prepared with a 600 °C process temperature at 100 mm/s, however none was evidenced at 400 mm/s for the same process temperature.
Christopher Stokesgriffin - One of the best experts on this subject based on the ideXlab platform.
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the effect of processing temperature and placement rate on the short Beam Strength of carbon fibre peek manufactured using a laser tape placement process
Composites Part A-applied Science and Manufacturing, 2015Co-Authors: Christopher Stokesgriffin, Paul CompstonAbstract:Abstract The ability of a modern near infra-red laser tape placement system to produce high-quality laminates is investigated by performing short Beam Strength tests on samples manufactured at different process temperatures from 400 °C to 600 °C at placement rates of 100 mm/s and 400 mm/s. The temperature history in tape placement is highly dynamic and the correlation between the process control temperature, laser power and the consolidation temperature is not well understood. The complete temperature history was therefore estimated with a previously developed optical-thermal model and validated using long wave infra-red imaging. Short Beam Strengths equivalent to conventional manufacturing methods were found for placement rates of 400 mm/s. Failure modes of the samples were elucidated by scanning electron microscopy of the fracture surfaces. Signs of degradation were observed on samples prepared with a 600 °C process temperature at 100 mm/s, however none was evidenced at 400 mm/s for the same process temperature.
Masoud Mehrraoufi - One of the best experts on this subject based on the ideXlab platform.
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Impact of column-to-Beam Strength ratio on the seismic response of steel MRFs
Bulletin of Earthquake Engineering, 2015Co-Authors: Arash E. Zaghi, Siavash Soroushian, Ahmad Itani, E. Manos Maragakis, Gokhan Pekcan, Masoud MehrraoufiAbstract:The strong-column/weak-Beam seismic design concept in moment resisting frames is perhaps one of the least well-understood design provisions. This study is aimed at improving the understanding of the effect of column-to-Beam Strength ratio (CBSR) on several seismic performance measures. Through nonlinear analyses of 3-, 9-, and 20-story moment resisting frame, the impacts of CBSR on member ductility demands, maximum inter-story drifts, and floor acceleration amplifications are investigated. For each frame, the value of CBSR is varied by changing the yield Strength of the material and/or by altering sizes of the columns. The probabilities of exceeding certain performance limits are investigated through fragility analyses. The single curvature bending of the columns within a story is found to be inevitable due to the participation of higher modes of vibration. Consequently, under large ground motions, the yielding of the columns is expected even for CBSRs larger than 2.0. The fragility relationships were used to calculate the design force modification factors needed for achieving a comparable probability of column yielding for different values of CBSR. The values of the yield base shear and the inter-story drifts were found to depend more on the Strength of the Beams than the value of CBSR. The floor acceleration amplification was found to be the least sensitive demand parameter to the CBSR.
Jing Bo Liu - One of the best experts on this subject based on the ideXlab platform.
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Realization of Strong Column-Weak Beam Failure Mode for Concrete-Filled Square Steel Tubular Frame Structure
Advanced Materials Research, 2012Co-Authors: Jing Bo LiuAbstract:Strong column-weak Beam failure mode is considered to be a preferable mode for its large capability to absorb earthquake energy and prevent collapse. However, for composite frames composed of steel-concrete composite Beams and concrete-filled steel tubular (CFST) columns, strong column-weak Beam design methods are not given in Chinese codes. The column-to-Beam Strength ratio is one of the most important factors that influence the failure mode of frame structures. Moreover, large axial compression ratio of columns may cut down the actual bending capacity of columns, and thus has an adverse effect upon the realization of strong column-weak Beam failure mode. In order to investigate the influence of column-to-Beam Strength ratio and axial compression ratio on the failure mode of concrete-filled square steel tubular frame structures, pushover analysis of a five-story three-bay composite frames with various column-to-Beam Strength ratios and axial compression ratios are carried out. Based on the analysis results, suggestions about the reasonable value of column-to-Beam Strength ratio with different axial compression ratios of columns are given to ensure the realization of strong column-weak Beam failure mode for concrete-filled square steel tubular frame structures.
Arash E. Zaghi - One of the best experts on this subject based on the ideXlab platform.
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Impact of column-to-Beam Strength ratio on the seismic response of steel MRFs
Bulletin of Earthquake Engineering, 2015Co-Authors: Arash E. Zaghi, Siavash Soroushian, Ahmad Itani, E. Manos Maragakis, Gokhan Pekcan, Masoud MehrraoufiAbstract:The strong-column/weak-Beam seismic design concept in moment resisting frames is perhaps one of the least well-understood design provisions. This study is aimed at improving the understanding of the effect of column-to-Beam Strength ratio (CBSR) on several seismic performance measures. Through nonlinear analyses of 3-, 9-, and 20-story moment resisting frame, the impacts of CBSR on member ductility demands, maximum inter-story drifts, and floor acceleration amplifications are investigated. For each frame, the value of CBSR is varied by changing the yield Strength of the material and/or by altering sizes of the columns. The probabilities of exceeding certain performance limits are investigated through fragility analyses. The single curvature bending of the columns within a story is found to be inevitable due to the participation of higher modes of vibration. Consequently, under large ground motions, the yielding of the columns is expected even for CBSRs larger than 2.0. The fragility relationships were used to calculate the design force modification factors needed for achieving a comparable probability of column yielding for different values of CBSR. The values of the yield base shear and the inter-story drifts were found to depend more on the Strength of the Beams than the value of CBSR. The floor acceleration amplification was found to be the least sensitive demand parameter to the CBSR.