Anthony Favaloro

Coupling anisotropic viscosity and fiber orientation in applications to squeeze flow

The influence of anisotropic viscosity on fiber orientation evolution in classic squeeze flow is examined with a viscous fiber suspension of specified initial orientation state. The components of the anisotropic viscosity tensor for a well dispersed and collimated fiber suspension developed in micromechanical analyses earlier by one of the authors were combined in an orientation averaging approach to produce the effective suspension viscosity components for arbitrary orientation states. A coupled anisotropic viscosity constitutive relationship was numerically implemented into a displacement-based finite element code for nonlinear analysis of flow and fiber orientation. The numerical method was verified by agreement between predicted and observed responses for a single element subjected to canonical states of deformation. Evolution of fiber orientation during the deformation processes was confirmed by analytic predictions. This approach was validated by examining the squeeze flow of a fiber suspension stud...

Simulation of prepreg platelet compression molding: Method and orientation validation

Prepreg platelet molding compounds (PPMCs) offer improved performance potential as compared to short-fiber composites and increased geometrical complexity as compared to continuous fiber composites. The increased adoption of PPMCs in automotive and aerospace applications necessitates the development of predictive tools for determining the final orientation state in complex geometries produced through molding flows. Due to the large geometric scale of platelets as compared to molded geometry scales, the orientation structure of PPMCs is spatially nonsmooth, thereby eliminating the requisite separation of scales utilized by typical molding simulation approaches. Additionally, the large fiber volume fraction and fiber length in platelets yield highly anisotropic flow behavior, as manifested in the resistance to stretching deformations along platelet fiber directions. Thus, the goal of this work is to present the development, implementation, and validation of a flow simulation approach for PPMCs accounting for fiber direction and platelet normal direction evolution with coupled anisotropic viscous behavior. The simulation approach is implemented using the smoothed particle hydrodynamics method. To validate the proposed approach, a pin bracket geometry is manufactured from a charge with the orientation state measured by computed tomography (CT). The final orientation state determined by the flow simulation predictions and by measuring the orientation state of the final bracket by CT is compared to validate the predictions.Prepreg platelet molding compounds (PPMCs) offer improved performance potential as compared to short-fiber composites and increased geometrical complexity as compared to continuous fiber composites. The increased adoption of PPMCs in automotive and aerospace applications necessitates the development of predictive tools for determining the final orientation state in complex geometries produced through molding flows. Due to the large geometric scale of platelets as compared to molded geometry scales, the orientation structure of PPMCs is spatially nonsmooth, thereby eliminating the requisite separation of scales utilized by typical molding simulation approaches. Additionally, the large fiber volume fraction and fiber length in platelets yield highly anisotropic flow behavior, as manifested in the resistance to stretching deformations along platelet fiber directions. Thus, the goal of this work is to present the development, implementation, and validation of a flow simulation approach for PPMCs accounting fo...

Prepreg Platelet Morphology and Scale Effects on Molding Processability

Unidirectional, prepreg platelet-based molding systems have gained considerable attention for manufacturing parts with moderate performance and processability metrics. A numerical study of squeeze flow, using a recently developed technique for coupled flow simulation and fiber orientation analysis, has been performed to investigate the effects of the platelet morphology on the processing of prepreg platelet based composite molding systems. Two competing effects have been shown to drive the processability of such a material: (i) increasing extensional viscosity due to increasing platelet length and (ii) increasing apparent viscosity due to increasing uniformity of orientation distribution. By adjusting the platelet dimensions, the above phenomena have been isolated in the numerical simulations to demonstrate their relative importance on the processability of platelet based molding systems.