Experimental and Numerical Investigation Into the Impact of Aging, Flow, and Scaling on Discontinuous Fiber Composite and Hybrid Structures

Abstract

Discontinuous fiber composites (DFCs) have garnered the interest of many industries due to their manufacturing capabilities, and potential for recycling of thermoset prepregs. DFCs are manufactured by chopping conventional continuous fiber prepreg into platelets. This allows for ease of compression and injection molding, which is suitable for high volume production and cheaper manufacturing. Furthermore, these platelets do not need to be made using virgin material, and the trim from manufacturing, that would have ended up in a land fill, can be used to make DFCs. This further brings down cost of production when using this material. However, there are still some unanswered questions that need to be answered before there is widespread adoption of DFCs for recycling and other applications. First of all, when using scrap thermoset prepreg, there will be ambient curing that may have effects on the performance of DFCs. Secondly, due to the random nature of the mesostructure, there is a need to find ways to control the variation between specimens. Thirdly, due to the complex geometries of DFC parts, there will always be regions of low and high flow that will cause a biased orientation of the platelets, thus there is a need to understand how this effects the mechanical behavior. Finally, there is a lack of computational tools that allow for the prediction of the behavior of DFCs. This leads to lengthy and costly physical testing to certify parts made with DFCs. This study aims to address these aforementioned questions by experimentally and numerically investigating (1) mechanical and fracture properties of DFCs made using aged thermoset prepreg, (2) the effects platelet size, thickness, and adding continuous fiber plies to the outer surface of a DFC core has on flexure properties and its variation, (3) the effects that platelet flow conditions have on tensile properties, and (4) the behavior of a complex 3D part made using DFC. By building computational tools to predict experimental results, the design of DFC parts can be safer and more efficient.