scholarly journals Modeling and Experimental Validation of the VARTM Process for Thin-Walled Preforms

Polymers ◽  
2019 ◽  
Vol 11 (12) ◽  
pp. 2003
Author(s):  
Da Wu ◽  
Ragnar Larsson ◽  
Mohammad S. Rouhi
Keyword(s):  
Shell Model ◽  
Computational Efficiency ◽  
Large Scale ◽  
Strongly Coupled ◽  
Thin Walled Structures ◽  
Simulation Based ◽  
Thin Walled ◽  
High Computational Efficiency ◽  
Insight Into ◽  
Vartm Process

In this paper, recent shell model is advanced towards the calibration and validation of the Vacuum-assisted Resin Transfer Molding (VARTM) process in a novel way. The model solves the nonlinear and strongly coupled resin flow and preform deformation when the 3-D flow and stress problem is simplified to a corresponding 2-D problem. In this way, the computational efficiency is enhanced dramatically, which allows for simulations of the VARTM process of large scale thin-walled structures. The main novelty is that the assumptions of the neglected through-thickness flow and the restricted preform deformation along the normal of preform surface suffice well for the thin-walled VARTM process. The model shows excellent agreement with the VARTM process experiment. With good accuracy and high computational efficiency, the shell model provides an insight into the simulation-based optimization of the VARTM process. It can be applied to either determine locations of the gate and vents or optimize process parameters to reduce the deformation.

scholarly journals Experimental Nondestructive Test for Estimation of Buckling Load on Unstiffened Cylindrical Shells Using Vibration Correlation Technique

2015 ◽  
Vol 2015 ◽  
pp. 1-8 ◽  
Author(s):  
Kaspars Kalnins ◽  
Mariano A. Arbelo ◽  
Olgerts Ozolins ◽  
Eduards Skukis ◽  
Saullo G. P. Castro ◽  
...  
Keyword(s):  
Large Scale ◽  
Numerical Models ◽  
Cylindrical Shells ◽  
Laser Scanner ◽  
Experimental Tests ◽  
Buckling Load ◽  
Correlation Technique ◽  
Thin Walled Structures ◽  
Instability Point ◽  
Thin Walled

Nondestructive methods, to calculate the buckling load of imperfection sensitive thin-walled structures, such as large-scale aerospace structures, are one of the most important techniques for the evaluation of new structures and validation of numerical models. The vibration correlation technique (VCT) allows determining the buckling load for several types of structures without reaching the instability point, but this technique is still under development for thin-walled plates and shells. This paper presents and discusses an experimental verification of a novel approach using vibration correlation technique for the prediction of realistic buckling loads of unstiffened cylindrical shells loaded under axial compression. Four different test structures were manufactured and loaded up to buckling: two composite laminated cylindrical shells and two stainless steel cylinders. In order to characterize a relationship with the applied load, the first natural frequency of vibration and mode shape is measured during testing using a 3D laser scanner. The proposed vibration correlation technique allows one to predict the experimental buckling load with a very good approximation without actually reaching the instability point. Additional experimental tests and numerical models are currently under development to further validate the proposed approach for composite and metallic conical structures.

scholarly journals A shell model for resin flow and preform deformation in thin-walled composite manufacturing processes

2019 ◽  
Vol 13 (6) ◽  
pp. 923-937 ◽  
Author(s):  
Da Wu ◽  
Ragnar Larsson
Keyword(s):  
Shell Model ◽  
Large Scale ◽  
Surface Flow ◽  
Flow In Porous Media ◽  
Resin Flow ◽  
Problem Size ◽  
Fiber Preform ◽  
Plane Flow ◽  
Numerical Example ◽  
Thin Walled

AbstractThe paper proposes a novel approach to model the in-plane resin flow in deformable thin-walled fiber preforms for liquid composite molding processes. By ignoring the through-thickness flow in large scale thin-walled components, the 3-D resin flow is simplified to an in-plane flow inside the preform by a specialized divergence theorem. Shell kinematics are used to describe the fiber preform deformation, and the compressible flow is modeled in the context of the free surface flow in porous media. For simplicity and efficiency, the normal stretch, which is driven by the internal fluid and applied external pressure, represents the fiber preform expansion and compression. As compared with full 3-D models, the proposed shell model significantly reduces the problem size, while it still represents the primary physical phenomena during the process. The effects of neglecting the through-thickness flow are illustrated in a numerical example that compares the flow for a set of preforms with different thickness. The model is demonstrated from the numerical example of the mold filling in a doubly curved thin-walled fiber preform. Due to the applied vacuum and the consequent resin flow motion, the relevant deformation of the preform is observed.

Compliant assembly deviation analysis of large-scale thin-walled structures in different clamping schemes via ANCF

2019 ◽  
Vol 40 (2) ◽  
pp. 305-317
Author(s):  
Xun Xu ◽  
Haidong Yu ◽  
Yunyong Li ◽  
Xinmin Lai
Keyword(s):  
Large Scale ◽  
Geometrical Parameters ◽  
Plate Element ◽  
Equilibrium Equations ◽  
Assembly Quality ◽  
Content Type ◽  
Thin Walled Structures ◽  
Quadrilateral Plate ◽  
Thin Walled ◽  
Assembly Deviation

Purpose The structure stiffness is greatly affected by the fixture constraints during assembly due to the flexibility of large-scale thin-walled structures. The compliant deformation of structures is usually not consistent for the non-uniform stiffness in various clamping schemes. The purpose of this paper is to investigate the correlation between the assembly quality and the clamping schemes of structures with various initial deviations and geometrical parameters, which is based on the proposed irregular quadrilateral plate element via absolute nodal coordinate formulation (ANCF). Design/methodology/approach Two typical clamping schemes are specified for the large-scale thin-walled structures. Two typical deviation modes are defined in both free and clamping states in the corresponding clamping schemes. The new irregular quadrilateral plate element via ANCF is validated to analyze the compliant deformation of assembled structures. The quasi-static force equilibrium equations are extended considering the factors of clamping constraints and geometric deviations. Findings The initial deviations and geometrical parameters strongly affect the assembly deviations of structures in two clamping schemes. The variation tendencies of assembly deviations are demonstrated in details with the circumferential clamping position and axial clamping position in two clamping schemes, providing guidance to optimize the fixture configuration. The assembly quality of structures with deviations can be improved by configuration synthesis of the clamping schemes. Originality/value Typical over-constraint clamping schemes and deviation modes in clamping states are defined for large-scale thin-walled structures. The plate element via ANCF is extended to analyze the assembly deviations of thin-walled structures in various clamping schemes. Based on the proposed theoretical model, the effects of clamping schemes and initial deviations on the deformation and assembly deviation propagation of structures are investigated.

scholarly journals Stability of thin walled structures strongly coupled with contact

PAMM ◽  
2009 ◽  
Vol 9 (1) ◽  
pp. 257-258
Author(s):  
Ridvan Izi ◽  
Karl Schweizerhof ◽  
Alexander Konyukhov
Keyword(s):  
Strongly Coupled ◽  
Thin Walled Structures ◽  
Thin Walled

Development of structure within the turbulent wake of a porous body. Part 1. The initial formation region

1996 ◽  
Vol 329 ◽  
pp. 103-115 ◽  
Author(s):  
Z. Huang ◽  
J. F. Keffer
Keyword(s):  
Large Scale ◽  
Low Frequency ◽  
Vortex Method ◽  
Body Part ◽  
Shear Layers ◽  
Turbulent Wake ◽  
Small Scale ◽  
Discrete Vortex ◽  
Simulation Based ◽  
Insight Into

This paper deals with the initial region (x/d = 1 to 20) of a turbulent wake generated by a mesh strip. The purpose of the study is to identify the formation mechanism of the large-scale vortices which have developed by the end of this zone. The region is characterized by the evolution and interaction of two parallel shear layers generated at the edges of the mesh. Multi-point hot-wire velocity measurements establish that the merging and interaction of the small-scale eddies account for the formation of the large-scale vortices. A numerical simulation based on a discrete vortex method was carried out to gain further insight into the interaction between the two shear layers. Both the experimental and numerical results suggest that low-frequency perturbation plays an important role in the communication between the two shear layers.

Sign in / Sign up

Export Citation Format

Share Document