Mesoscale Process Modeling of a Thick Pultruded Composite with Variability in Fiber Volume Fraction

Area of Science:

• Materials Science
• Composite Materials Engineering
• Mechanical Engineering

Background:

• Pultruded fiber-reinforced polymer composites exhibit microstructural nonuniformity, particularly in fiber volume fraction (Vf).
• Variability in Vf distribution can significantly influence process-induced residual stresses.
• Existing pultrusion process models have inadequately addressed the impact of non-uniform Vf distribution.

Purpose of the Study:

• To characterize the fiber volume fraction (Vf) distribution and its nonuniformity in unidirectional fiber-reinforced pultruded profiles.
• To investigate the effect of this Vf nonuniformity on process-induced residual stresses using a developed mesoscale model.
• To analyze the influence of Vf gradients on temperature, cure degree, and residual stress evolution.

Main Methods:

• Optical light microscopy was employed to characterize the Vf distribution in pultruded composite profiles.
• A mesoscale thermal-chemical-mechanical process model was developed for the pultrusion process.
• Local constitutive material behavior was defined based on corresponding Vf values in representative volume elements within the model.

Main Results:

• The study confirmed significant Vf nonuniformity across the cross-section of the pultruded profile.
• Nonuniform Vf distribution was found to increase the magnitude and scatter of predicted residual stresses.
• A Vf gradient promoted tensile residual stresses in the core and compressive residual stresses in outer regions.

Conclusions:

• It is crucial to incorporate the effects of fiber distribution nonuniformity for accurate residual stress estimations in pultruded composites.
• The developed numerical framework provides an efficient tool for studying the impact of Vf nonuniformity on residual stresses.
• Understanding Vf distribution is key to optimizing composite performance and predicting failure mechanisms.