No description available.

No description available.

No description available.

Autoclave processing of large scale, one-piece structural parts made of carbon fiber-reinforced polymer composite materials is the key to decreasing manufacturing costs while at the same time increasing quality. Nonetheless, even in manufacturing simple flat parts, residual strains and stresses are unavoidable. For structural design purposes and to aid in the assembly procedures, it is desirable to have proven numerical tools that can be used to predict these residual geometrical and material properties in advance, thus avoid the costly experimental trial and error methods. A 2-D finite element-based code, COMPRO, has previously been developed in-house for predicting autoclave process-induced deformations and residual stresses in composite parts undergoing an entire cure cycle. To simulate the tool-part interaction, an important source of residual deformations/stresses, COMPRO used a non-zero thickness elastic shear layer as its only interface option. Moreover, the code did not account for the large deformations and strains and the resulting nonlinear effects that can arise during the early stages of the cure cycle when the material is rather compliant. In the present work, a contact surface employing a penalty method formulation is introduced at the tool-part interface. Its material-dependent parameters are a function of temperature, degree of cure, pressure and so forth. This makes the stick-slip condition plus separation between the part and the tool possible. The large displacements/rotations and large shear strains that develop at the early stages of the cure cycle when the resin has a very low elastic modulus provided the impetus to include a large strain/deformation option in COMPRO. A new “co-rotational stress formulation” was developed and found to provide a robust method for numerical treatment of very large deformation/strain problems involving anisotropic materials of interest here. Several verification and validation examples are used to calibrate the contact interface parameters and to demonstrate the correctness of implementation and the accuracy of the proposed method. A number of comparisons are made with exact solutions, other methods, other experiments and the same models in other commercial codes. Finally, several interesting cases are examined to explore the results of COMPRO predictions with the added options.

Autoclave processing of large scale, one-piece structural parts made of carbon fiber-reinforced polymer composite materials is the key to decreasing manufacturing costs while at the same time increasing quality. Nonetheless, even in manufacturing simple flat parts, residual strains and stresses are unavoidable. For structural design purposes and to aid in the assembly procedures, it is desirable to have proven numerical tools that can be used to predict these residual geometrical and material properties in advance, thus avoid the costly experimental trial and error methods. A 2-D finite element-based code, COMPRO, has previously been developed in-house for predicting autoclave process-induced deformations and residual stresses in composite parts undergoing an entire cure cycle. To simulate the tool-part interaction, an important source of residual deformations/stresses, COMPRO used a non-zero thickness elastic shear layer as its only interface option. Moreover, the code did not account for the large deformations and strains and the resulting nonlinear effects that can arise during the early stages of the cure cycle when the material is rather compliant. In the present work, a contact surface employing a penalty method formulation is introduced at the tool-part interface. Its material-dependent parameters are a function of temperature, degree of cure, pressure and so forth. This makes the stick-slip condition plus separation between the part and the tool possible. The large displacements/rotations and large shear strains that develop at the early stages of the cure cycle when the resin has a very low elastic modulus provided the impetus to include a large strain/deformation option in COMPRO. A new “co-rotational stress formulation” was developed and found to provide a robust method for numerical treatment of very large deformation/strain problems involving anisotropic materials of interest here. Several verification and validation examples are used to calibrate the contact interface parameters and to demonstrate the correctness of implementation and the accuracy of the proposed method. A number of comparisons are made with exact solutions, other methods, other experiments and the same models in other commercial codes. Finally, several interesting cases are examined to explore the results of COMPRO predictions with the added options.

Autoclave processing of large scale, one-piece structural parts made of carbon fiber-reinforced polymer composite materials is the key to decreasing manufacturing costs while at the same time increasing quality. Nonetheless, even in manufacturing simple flat parts, residual strains and stresses are unavoidable. For structural design purposes and to aid in the assembly procedures, it is desirable to have proven numerical tools that can be used to predict these residual geometrical and material properties in advance, thus avoid the costly experimental trial and error methods. A 2-D finite element-based code, COMPRO, has previously been developed in-house for predicting autoclave process-induced deformations and residual stresses in composite parts undergoing an entire cure cycle. To simulate the tool-part interaction, an important source of residual deformations/stresses, COMPRO used a non-zero thickness elastic shear layer as its only interface option. Moreover, the code did not account for the large deformations and strains and the resulting nonlinear effects that can arise during the early stages of the cure cycle when the material is rather compliant. In the present work, a contact surface employing a penalty method formulation is introduced at the tool-part interface. Its material-dependent parameters are a function of temperature, degree of cure, pressure and so forth. This makes the stick-slip condition plus separation between the part and the tool possible. The large displacements/rotations and large shear strains that develop at the early stages of the cure cycle when the resin has a very low elastic modulus provided the impetus to include a large strain/deformation option in COMPRO. A new “co-rotational stress formulation” was developed and found to provide a robust method for numerical treatment of very large deformation/strain problems involving anisotropic materials of interest here. Several verification and validation examples are used to calibrate the contact interface parameters and to demonstrate the correctness of implementation and the accuracy of the proposed method. A number of comparisons are made with exact solutions, other methods, other experiments and the same models in other commercial codes. Finally, several interesting cases are examined to explore the results of COMPRO predictions with the added options. / Applied Science, Faculty of / Civil Engineering, Department of / Graduate

This work aims at providing a numerical tool for the efficient design of the multidirectional carbon fiber reinforced composite material by means of finite element simulations. Abaqus/ CAE v 6.9-1 software has been used to establish a 3D model for simulation of the tensile test on the composite specimen. The aim of this analysis of multidirectional carbon fiber reinforced composite is to predict the strain and stress distribution in different plies through thickness. Tensile test experiment was carried out and the result was analyzed by ARAMIS to calculate the young’s modulus, stress, loads and strain of the composite specimen. The numerical model was compared against the result obtained from tensile test experiment to arrive at meaningful results for validation. This is done in order to understand the mechanical strength and strain at failure of the composite material. In this work three types of CFRP composite specimens are used, all have same 15 no. of ply but stacked in different orientation. It is found out that mechanical strength, failure load and strain differ slightly depending on this different ply orientation. A series of different modeling technique has also been done to verify the best modeling technique. The micromechanics of composite material is complex and the experimental predictions are time consuming and expensive. Though using FEM frequently solves the problem.

We investigate the EM properties of four different type composites which are nylon and liquid-crystal polymer with carbon fiber filler composites, woven continuous carbon fiber epoxy composites(balanced twill structure, plain weave structure, uni-direction weave structure), and liquid-crystal polymer with carbon nanotubes filler composites. By comparison of fabrication methods, cost and weight of the optical transceiver module housings, and shielding effectiveness under plane wave and near-field conditions, the woven continuous carbon fiber epoxy composites(balanced twill structure and plain weave structure) show lower cost, lighter weight, and higher EM shielding effectiveness than the other types of composites. Furthermore, they also perform good radiation susceptibility in our measurements. For these reasons, the proposed woven continuous carbon fiber epoxy composite package for an optical transceiver is suitable for use in a low-cost light wave transmission system.

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Electrospinning has been recognized as an efficient technique for the fabrication of polymer fibers. These electrospun fibers have many applications across a broad range of industries. In this research, optical transparent composites were successfully fabricated by embedding polyacrylonitrile (PAN) hollow nanofibers into poly (methyl methacrylate) (PMMA) matrix. The hollow PAN nanofibers were prepared by coaxial electrospinning. The PAN was used as the shell solution, and the mineral oil was used as the core solution. The resulting fibers were then etched with octane to remove the mineral oil from the core. The hollow PAN fibers were then homogeneously distributed in PMMA resins to fabricate the composite. The morphology, transmittance and mechanical properties of the PAN/PMMA composite were then characterized with an ESEM, TEM, tensile testing machine, UV-vis spectrometer and KD2 Pro Decagon device. The results indicated that the hollow nanofibers have relatively uniform size with one-dimensional texture at the walls. The embedded PAN hollow nanofibers significantly enhanced the tensile stress and the Young's modulus of the composite (increased by 58.3% and 50.4%, respectively), while having little influence on the light transmittance of the composite. The KD2 Pro device indicated that the thermal conductivity of the PMMA was marginally greater than the PAN/PMMA composite by 2%. This novel transparent composite could be used for transparent armor protection, window panes in vehicles and buildings, and airplane windshield etc.