Fast liquid composite molding simulation of unsaturated flow in dual-scale fiber mats using the imbibition characteristics of a fabric-based unit cell

2010 ◽  
Vol 31 (10) ◽  
pp. 1790-1807 ◽  
Author(s):  
Hua Tan ◽  
Krishna M. Pillai
Keyword(s):  
Unsaturated Flow ◽  
Unit Cell ◽  
Liquid Composite Molding ◽  
Fiber Mats ◽  
Composite Molding ◽  
Dual Scale

First Steps Towards Quantitative Validation of the Unsaturated-Flow Theories in Liquid Composite Molding

2003 ◽  
Author(s):  
Tonmoy Roy ◽  
Baiju Z. Babu ◽  
Krishna M. Pillai
Keyword(s):  
Pore Volume ◽  
Unsaturated Flow ◽  
Volume Ratio ◽  
Mold Filling ◽  
Inlet Pressure ◽  
Liquid Composite Molding ◽  
Fiber Mats ◽  
Pressure History ◽  
Composite Molding ◽  
Dual Scale

In liquid composite molding technologies such as Resin Transfer Molding (RTM), a thermoset resin is injected into a mold cavity with a pre-placed preform made of fiber mats to create a cured part. In order to improve the physics of resin flow in dual-scale (woven, stitched or braided) fiber mats, the authors carried out many transient 1-D mold-filling experiments to investigate the onset of unsaturated flow through the inlet-pressure history. Their study revealed that the measured pressure history, which droops downwards for dual-scale fiber mats, is at a variance with the linear pressure profile predicted by state-of-the-art Liquid Composite Molding (LCM) mold-filling simulation physics. It was also observed that the drooping of the inlet pressure increases with an increase in the compression of fiber mats. In this paper, the correlation between a previously proposed dimensionless number pore volume ratio and the droop in the inlet pressure history has been sought. Studying the micrographs of composite samples, pore volume ratio is measured for various fiber mat compression. It is observed that the droop in the inlet pressure profiles increase with an increase in the pore volume ratio. This is the first attempt to quantitatively validate the previous theories on the unsaturated flow.

Investigation of Heat Transfer and Cure During the Unsaturated Flow in Woven, Stitched and Unbraided Mats

2003 ◽  
Author(s):  
Rajendra S. Jadhav ◽  
Krishna M. Pillai
Keyword(s):  
Unsaturated Flow ◽  
Polymer Matrix Composites ◽  
Numerical Study ◽  
Control Volume ◽  
Scale Model ◽  
Liquid Composite Molding ◽  
Matrix Composites ◽  
Fiber Mats ◽  
Significant Difference ◽  
Dual Scale

This numerical study investigates heat generation and cure during the unsaturated flow of thermosetting resins in woven, stitched or braided fiber mats during mold filling in liquid composite molding (LCM), a popular technology to manufacture polymer-matrix composites. This study is relevant to those mats, which can be characterized as a dual-scale porous medium. An iterative, control-volume approach, based on energy and cure balances in a two-layer model representing fiber tows and gaps between tows, is used for developing discretized equations for average temperatures and cures in the tows and gaps respectively. A significant difference in the temperatures and cures of the gap and tow regions is observed. The proposed model deviates significantly from the conventional single-scale model used in most LCM simulations and highlights the need to adopt a different approach in modeling cure and temperature in dual-scale fiber mats.

Experimental study of saturation by visible light transmission in dual-scale fibrous reinforcements during composite manufacturing

2017 ◽  
Vol 36 (23) ◽  
pp. 1693-1711 ◽  
Author(s):  
F LeBel ◽  
É Ruiz ◽  
F Trochu
Keyword(s):  
Visible Light ◽  
Light Transmission ◽  
Void Formation ◽  
In Situ Monitoring ◽  
Injection System ◽  
Computer Assisted ◽  
Liquid Composite Molding ◽  
Composite Molding ◽  
The Impact ◽  
Dual Scale

A new in situ monitoring strategy is proposed to study void formation during real-time impregnation of dual-scale fibrous reinforcements in liquid composite molding. Void content data from burn-off tests are used to calibrate a refractive index matching approach based on two optical principles: Beer–Lambert and Fresnel laws. Once calibrated, this approach based on visible light transmission is used to study the impact of key process parameters on the saturation footprint of dual-scale fibrous reinforcements during and after mold filling. The injection parameters investigated are the flow front velocity, the pressure distribution inside the mold cavity, the bleeding flow rate, and the mold packing pressure. The experimental setup is a computer-assisted injection system and a transparent resin transfer molding mold is used to perform unidirectional injections. A vinyl ester resin is injected through E-glass bidirectional non-crimp fabrics under various manufacturing conditions. This investigation not only confirms the decreasing trend in void formation by mechanical entrapment of air with the decrease in impregnation velocity, as it converges toward the optimal impregnation conditions for this fibrous reinforcement reported in previous studies, but it also brings insights on void dissolution and transport in liquid composite molding.

Modeling void formation and unsaturated flow in liquid composite molding processes: a survey and review

2011 ◽  
Vol 30 (11) ◽  
pp. 957-977 ◽  
Author(s):  
Chung Hae Park ◽  
Lee Woo
Keyword(s):  
Unsaturated Flow ◽  
State Of The Art ◽  
Void Formation ◽  
Pressure Profile ◽  
Liquid Composite Molding ◽  
Simulation Studies ◽  
Apparent Permeability ◽  
Composite Molding ◽  
Unsaturated Flows ◽  
Key Parameter

In this study, we present a review of the modeling of void formation and unsaturated flow in liquid composite molding processes. We examine modeling efforts considering all the mechanisms involved such as void formation and transport, bubble compression, and gas dissolution. In particular, the capillary number is identified as a key parameter for void formation and transport. Numerical simulation studies are reviewed, and a state-of-the-art is presented. The influence of microvoids on the global resin flow is also investigated. To model the unsaturated flow more accurately, we suggest considering the surface tension or capillary pressure, variation in permeability in terms of saturation and fiber displacement, as well as tow saturation. From this investigation, the apparent permeability and pressure profile in saturated and unsaturated flows are compared.

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