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Frank Abdi - One of the best experts on this subject based on the ideXlab platform.

  • A Study of Ply Thickness and Angle Designs for Preventing Permeability of the IM7/977-2 Polymer Composite Cryogenic Tank
    47th AIAA ASME ASCE AHS ASC Structures Structural Dynamics and Materials Conference<BR> 14th AIAA ASME AHS Adaptive Structures Conference<BR&, 2006
    Co-Authors: Frank Abdi, Ra Y Kim
    Abstract:

    Ply angle and thickness designs for preventing micro crack development in an IM7/977-2 pressurized disk were investigated through a numerical procedure. The composite disk was employed to represent a cryogenic tank dome under both fuel pressure and assembly loads. A micro mechanics model, the equivalent constraint model (ECM), was incorporated in the progressive failure finite element analyzer (GENOA) to address the initiation and evolution of micro cracks in the disk during the loading process. Two Laminate configurations, [45/90/-45/0]4s (Lay-up 1) and [0/0/16/-16/21/-21/26/-26/36/-36/45/45/55/-55/75/-75/90]s (Lay-up 2), were adopted in the ply angle effect study. The simulated micro crack density development in the disk made from Lay-up 1 shows better leakage resistance than the disk fabricated from Lay-up 2. To investigate the ply thickness design in preventing permeability, certain layers in the 32-layer Quasi-Isotropic Laminate with per ply thickness 0.0052 inches (layup 1) were replaced with 0.0026-inch thick, highly cracking resistant plies in the disk. Simulation results show the 0.0026-inch thick layers in the pressurized disk play an importance role in stopping the leakage path formation through the disk thickness.

  • a study of ply thickness and angle designs for preventing permeability of the im7 977 2 polymer composite cryogenic tank
    47th AIAA ASME ASCE AHS ASC Structures Structural Dynamics and Materials Conference 14th AIAA ASME AHS Adaptive Structures Conference 7th, 2006
    Co-Authors: Frank Abdi, Ra Y Kim
    Abstract:

    Ply angle and thickness designs for preventing micro crack development in an IM7/977-2 pressurized disk were investigated through a numerical procedure. The composite disk was employed to represent a cryogenic tank dome under both fuel pressure and assembly loads. A micro mechanics model, the equivalent constraint model (ECM), was incorporated in the progressive failure finite element analyzer (GENOA) to address the initiation and evolution of micro cracks in the disk during the loading process. Two Laminate configurations, [45/90/-45/0]4s (Lay-up 1) and [0/0/16/-16/21/-21/26/-26/36/-36/45/45/55/-55/75/-75/90]s (Lay-up 2), were adopted in the ply angle effect study. The simulated micro crack density development in the disk made from Lay-up 1 shows better leakage resistance than the disk fabricated from Lay-up 2. To investigate the ply thickness design in preventing permeability, certain layers in the 32-layer Quasi-Isotropic Laminate with per ply thickness 0.0052 inches (layup 1) were replaced with 0.0026-inch thick, highly cracking resistant plies in the disk. Simulation results show the 0.0026-inch thick layers in the pressurized disk play an importance role in stopping the leakage path formation through the disk thickness.

  • Prediction of Micro-crack Densities in IM7/977-2 Polymer Composite Laminates under Mechanical Loading at Room and Cryogenic Temperatures
    46th AIAA ASME ASCE AHS ASC Structures Structural Dynamics and Materials Conference, 2005
    Co-Authors: Xiaofeng Su, Frank Abdi
    Abstract:

    Monotonic and cyclic mechanical properties of a Quasi-Isotropic Laminate, IM7/977-2, at room and cryogenic temperatures were investigated through a numerical procedure. A micro mechanics model, the equivalent constraint model (ECM), was incorporated in the progressive failure finite element analyzer (GENOA) to address the initiation and evolution of micro cracks in polymer matrix during the entire fatigue process. The degradation of the Laminate stiffness due to micro crack multiplication was also evaluated using this numerical method. The simulation results agreed with the test observation reasonably well. This capability can be used as first level verification in the building block strategy approach.

Joan A. Mayugo - One of the best experts on this subject based on the ideXlab platform.

  • damage occurrence at edges of non crimp fabric thin ply Laminates under off axis uniaxial loading
    Composites Science and Technology, 2014
    Co-Authors: G Guillame, Pete Linde, A Turo, J Rena, J. Costa, Joan A. Mayugo
    Abstract:

    Thin-ply based Laminates are a promising development in composite materials and are expected in the near future to outperform conventional Laminates in mechanical performance. A rational design with thin plies requires understanding the effect of ply thickness on each damage mechanism. This paper presents an experimental investigation into damage occurrence in a Quasi-Isotropic Laminate made from thin-ply, bi-axial, Non-Crimp-Fabric (NCF), under different off-axis uniaxial loadings. The NCF layers are positioned through the Laminate thickness creating two regions, namely THICK and THIN (with and without ply clustering). Then, the onset and progress of three damage mechanisms (transverse matrix cracking, matrix crack induced delamination and free-edge delamination) for both regions are analyzed by monitoring the specimen’s free-edge. The results show that the critical region where damage occurs is that with ply clustering (THICK), whereas delamination originating from matrix cracks or free edge effects are delayed or even suppressed in the THIN region.

M Ramji - One of the best experts on this subject based on the ideXlab platform.

  • Post-buckling failure studies on Quasi-Isotropic CFRP panels under positive and negative in-plane shear loading
    2020
    Co-Authors: Kolanu, Naresh Reddy, Raju Gangadharan, M Ramji
    Abstract:

    The shear buckling performance of a flat Laminated composite structure depends on various factors like the nature of the applied load, lamina orthotropy, stacking sequence and the support boundary conditions. The emphasis of the current work is to decipher the effect of the direction of applied shear on the post-buckling response and failure of a Quasi-Isotropic carbon CFRP panel. A comprehensive experimental test campaign involving 3D-digital image correlation (DIC), acoustic emission (AE) and strain gaging techniques are used to capture the post-buckling deformation and the associated failure mechanisms in the CFRP test panels under positive and negative shear load. Further, a generic finite element based progressive damage model involving 3D Hashin’s failure criteria in conjunction with the cohesive zone model is developed in Abaqus software for simulating the intra and inter-laminar damages in the Quasi-Isotropic Laminate and later compared with the experimental results. The effect of positive and negative shear on the post-buckling response and the associated damage modes are investigated in detail. The outcome of the current investigations reveals that the direction of the shear load has a definite impact on the post-buckling response and failure behavior of the CFRP test panels

  • design of optimum patch shape and size for bonded repair on damaged carbon fibre reinforced polymer panels
    Materials & Design, 2014
    Co-Authors: Mohammad Kashfuddoja, M Ramji
    Abstract:

    Carbon fibre reinforced polymer (CFRP) composite Laminates have become popular for structural applications as they are lighter, stronger and tougher. But they are also susceptible to damage while in service. Damage in composite structures reduces its structural integrity and hence the service life. For improved service life, the damages need to be repaired so that structural integrity is restored. Adhesively bonded composite patch repair is one of the prominent technique used for restoring the structural integrity of the damaged part. Patch shape is one of the important parameter in composite repair performance and it needs to be investigated thoroughly. In the present work, a 3D finite element based study is carried out to investigate the influence of various patch shapes on repair efficiency. Damaged CFRP Laminates are repaired by symmetrical patch adhesively bonded over the damaged area. The panel analyzed is of pure unidirectional and Quasi-Isotropic Laminate sequences. The patch shapes considered are circle, rectangle, square, ellipse, octagon and oval. Stress concentration factor (SCF) is estimated before and after the repair to evaluate their efficiency. Also peel stress is considered for quantitative comparison. The SCF reduction and peel stress are compared for various patch shapes keeping constant patch volume. Stress based 3D-Hashin’s failure criterion is employed for predicting the strength at damage initiation along with failure modes in notched and repaired panel. Optimal patch shape is then brought-out based on higher repair efficiency. Finally, a genetic algorithm based approach in-conjunction with finite element analysis is used for the optimization of patch geometry and adhesive thickness in order to obtain higher repair performance.

Ra Y Kim - One of the best experts on this subject based on the ideXlab platform.

  • a study of ply thickness and angle designs for preventing permeability of the im7 977 2 polymer composite cryogenic tank
    47th AIAA ASME ASCE AHS ASC Structures Structural Dynamics and Materials Conference 14th AIAA ASME AHS Adaptive Structures Conference 7th, 2006
    Co-Authors: Frank Abdi, Ra Y Kim
    Abstract:

    Ply angle and thickness designs for preventing micro crack development in an IM7/977-2 pressurized disk were investigated through a numerical procedure. The composite disk was employed to represent a cryogenic tank dome under both fuel pressure and assembly loads. A micro mechanics model, the equivalent constraint model (ECM), was incorporated in the progressive failure finite element analyzer (GENOA) to address the initiation and evolution of micro cracks in the disk during the loading process. Two Laminate configurations, [45/90/-45/0]4s (Lay-up 1) and [0/0/16/-16/21/-21/26/-26/36/-36/45/45/55/-55/75/-75/90]s (Lay-up 2), were adopted in the ply angle effect study. The simulated micro crack density development in the disk made from Lay-up 1 shows better leakage resistance than the disk fabricated from Lay-up 2. To investigate the ply thickness design in preventing permeability, certain layers in the 32-layer Quasi-Isotropic Laminate with per ply thickness 0.0052 inches (layup 1) were replaced with 0.0026-inch thick, highly cracking resistant plies in the disk. Simulation results show the 0.0026-inch thick layers in the pressurized disk play an importance role in stopping the leakage path formation through the disk thickness.

  • A Study of Ply Thickness and Angle Designs for Preventing Permeability of the IM7/977-2 Polymer Composite Cryogenic Tank
    47th AIAA ASME ASCE AHS ASC Structures Structural Dynamics and Materials Conference<BR> 14th AIAA ASME AHS Adaptive Structures Conference<BR&, 2006
    Co-Authors: Frank Abdi, Ra Y Kim
    Abstract:

    Ply angle and thickness designs for preventing micro crack development in an IM7/977-2 pressurized disk were investigated through a numerical procedure. The composite disk was employed to represent a cryogenic tank dome under both fuel pressure and assembly loads. A micro mechanics model, the equivalent constraint model (ECM), was incorporated in the progressive failure finite element analyzer (GENOA) to address the initiation and evolution of micro cracks in the disk during the loading process. Two Laminate configurations, [45/90/-45/0]4s (Lay-up 1) and [0/0/16/-16/21/-21/26/-26/36/-36/45/45/55/-55/75/-75/90]s (Lay-up 2), were adopted in the ply angle effect study. The simulated micro crack density development in the disk made from Lay-up 1 shows better leakage resistance than the disk fabricated from Lay-up 2. To investigate the ply thickness design in preventing permeability, certain layers in the 32-layer Quasi-Isotropic Laminate with per ply thickness 0.0052 inches (layup 1) were replaced with 0.0026-inch thick, highly cracking resistant plies in the disk. Simulation results show the 0.0026-inch thick layers in the pressurized disk play an importance role in stopping the leakage path formation through the disk thickness.

Jean-jacques Barrau - One of the best experts on this subject based on the ideXlab platform.

  • Experimental analysis of CFRP Laminates subjected to Compression After Impact: the role of impact-induced cracks in failure
    Composite Structures, 2014
    Co-Authors: Samuel Rivallant, Christophe Bouvet, Elias Abi Abdallah, Bernhard Broll, Jean-jacques Barrau
    Abstract:

    This paper presents an experimental analysis of composite Laminates subjected to low velocity impact and compression after impact (CAI). Two types of CFRP specimens are studied: a highly oriented Laminate and a Quasi-Isotropic Laminate. Impact energy is chosen to obtain a dent depth less than or around the BVID level. 3D digital image correlation is used to make detailed analyses of plates behaviour during CAI. Even if the damage morphologies are very different, the study shows that, in both cases, classical global buckling of the plate and local buckling of the deLaminated subLaminates are accompanied by a crack on the impact face of the Laminate. This crack appears in the highly damaged zone, under the impactor, and propagates in the direction transverse to the loading direction in a stable way. It is shown to play an essential role in the final failure of the Laminate under compression.