A phenomenological model for fiber tow saturation of dual scale fabrics in liquid composite molding

Abstract

Advanced composites are manufactured by liquid composite molding by impregnating a thermoset resin into a stationary woven or stitched preform. For a successful injection, the manufactured part should fill all the empty spaces between the fiber tows and inside the fiber tows with the resin. The fiber tows in such preforms have orders of magnitude lower permeability than the regions between the fiber tows, which makes them difficult to fill and hence susceptible to formation of microvoids. Numerical simulations can address the filling of fiber tows but it is difficult to capture the essential physics of their filling in a model created entirely from first principles due to the complexity of the flow which involves anisotropic permeability of flow along and across a fiber tow, uneven packing, fiber sizing, capillarity and the treatment of entrapped air. Hence, in this article we adopt a phenomenological approach in which we compare some of the possible models with an experimental procedure. The experimental procedure provides a quantitative measure of the filling of fiber tows during the impregnation process. A numerical simulation based on the dual scale flow was developed with different constitutive models that described the filling of the fiber tows. The predictions of the different models are compared with the experimental results under different processing conditions to select the model that most accurately describes the tow filling behavior. POLYM. COMPOS., 31:1881–1889, 2010. © 2010 Society of Plastics Engineers.

Resin transfer molding (RTM) in polymer matrix composites

“…This feature allows one to investigate whether microvoids remain in the preform after the resin injection is discontinued at the end of the mold fi lling. 57,75 Simulation should be able to account for drapability of the fi ber preform • to investigate any wrinkle formation and also to predict the permeability of the sheared fi ber bundles. The permeabilities of the elements should be modifi ed accordingly to accurately refl ect the fl ow physics.…”

Simulation and experimental validation of mould tooling forces in RTM and CRTM for nonplanar components

“…The applications range from large parts with small production volumes to high‐volume production of smaller components, however all LCM processes offer significant advantages over open mould manufacturing processes, including better part quality/properties and reduced exposure to hazardous solvent emissions. To date, a number of simulations have been developed to model the filling phase of LCM processes , with later work extending this to cover the total forces experienced by the mould tools . Accurate tooling force predictions for LCM processes will allow reductions in lead time and setup costs through cost‐effective mould tool design and specification of appropriate supporting equipment (i.e., presses).…”

“…The rigid‐tool RTM process can be divided into four separate phases; preform preparation, mould closure, resin injection and finally resin cure . A fibrous preform is manufactured and inserted into a mould, which is then closed to a set cavity thickness, thereby determining the fiber volume fraction ( V f ) of the final part.…”

A Prediction Method for In-Plane Permeability and Manufacturing Applications in the VARTM Process

“…For example, Dong [18] increased the thickness of the distribution medium and/or the fiber preform to obtain equivalent material permeability. Besides, the Kozeny-Carman equation was commonly utilized to discuss the flow impregnates inside the porous material when considering the dimension of fiber [19][20][21][22]. Gebart [19] investigated the permeability of an idealized unidirectional reinforcement through the Darcy's law and Kozeny-Carman equation, and Rahatekar [21] used the permeability models through Kozeny-Carman equation to discuss the relationship between injection pultrusion pressure and process control parameters.…”