Session: 16-01-01: Poster Session: NSF-Funded Research (Grad & Undergrad)

Paper Number: 99899

99899 - A Hyper-Viscoelastic Model for Deformation Responses of Pre-Impregnated Tapes Under Processing Conditions 

    Advanced fiber-reinforced polymer matrix composites have been increasingly used in the transportation and aerospace industries over the past decades owing to their acclaimed durability, resistance to corrosion, design flexibility, and high stiffness-to-weight ratio. Thermoset and thermoplastic pre-impregnated tapes (prepregs) have been widely used in various composite manufacturing techniques including autoclave processing, thermoforming, and automated fiber placement (AFP). Shear of the prepregs is a key deformation mode affecting the deformation and defects such as wrinkles during the manufacturing processes. Therefore, a robust numerical modeling approach is needed to study the deformation of prepregs with focus on shear behaviors under processing conditions, helping the industry to achieve consistent high quality of composite products. Various modeling approaches have been proposed to simulate the shear of prepregs. However, seldom of them incorporates the viscoelastic effect of the resin and its dependence on the processing temperature and strain rate, which has been revealed in recent experimental studies.

    This study proposes a novel hyper-viscoelastic approach based on a strain energy density function, which is decomposed into a fiber part and a resin part. We assume that any complex deformation can be the combination of six basic deformation modes, including the tension/compression along three orthogonal directions as well as the shear in three orthogonal planes. It is also assumed that the fibers slide rather than shear when the prepregs are subject to pure shear external loads, and fibers can be stretched and bended when complex loads are applied. Hence, the fiber strain energy incorporates the stretch energy along the fiber direction and the bending energy approximated by the transverse shear form. The resin part consists of the transverse normal, in-plane shear, and transverse shear components. The first highlight of this study is to incorporate the viscous shear behavior of the resin at different temperatures and strain rates through a generalized Maxwell model, whose parameters are identified from the relaxation testing results of the resin conducted using a rheometer. The second feature is the consideration of the difference between the apparent shear strain of the prepregs and the shear strain of the resin by introducing a geometric parameter expressed as a function of the fiber spacing and the fiber diameter. The fiber properties are characterized by cantilever beam bending tests at temperatures above the melting point of the resin. The model is applied to three-point bending and in-plane shear simulations at different temperature and load rates to demonstrate the predictive capability.

Presenting Author: Qingxuan Wei Purdue University

Presenting Author Biography: Qingxuan Wei is currently a Ph.D. student working with Professor Dianyun Zhang at School of Aeronautics and Astronautics, Purdue University. Her research focuses on two concentrations: (1) simulating the deformation of dry fabrics during dry fabric draping process through a textile architecture-based mechanics model and a hyper-viscoelastic model; (2) development of multi-physics models to predict the deformation of fiber reinforcements and binding polymers in the liquid state. Prior to joining Purdue, Qingxuan received her Bachelor’s degree at Beihang University.

Authors:

Qingxuan Wei Purdue University
Lu Li Purdue University
Dianyun Zhang Purdue University