Viscoelastic Modeling Biobased Composites
In recent years there has been a resurgence of interest in the usage of natural fiber reinforced omposites in more advanced structural applications. As a result, the need for improving their mechanical properties, as well as service life modeling and predictions have arisen. Because of their bond type and structure, natural fibers and thermoset resins exhibit nonlinear viscoelastic behavior.
Time-temperature superposition (TTS) provides a useful tool to overcome the challenge of the long time required to perform the tests.
On the other hand Composites having high bio-based content with properties and costs rivaling those consisting of synthetic constituents are a goal of much current research. The obvious material choices — vegetable oil based resins and natural fibers — present the challenges of poor resin properties and weak fiber/matrix bonding, respectively. To overcome these limitations while maintaining high bio-content, several newly developed biobased resins from soybean oil are studies.
In this Project, which is a collaboration work with Center for Sustainable Materials Science (CSMS) at NDSU effect of treatment of flax fiber as well as matrix (vinyl ester, epoxy and novel bio-based resins) on mechanical properties of ensuing composites in short-term as well as long-term ( creep and accelerated weathering) is investigated.
The effect of alkaline treatment of flax fiber, zein treatment and and addition of 1% acrylic resin to matrices, has been investigated. In order to evaluate the long-term behavior, creep compliance master curves were generated using the time-temperature superposition principle. Results suggests that fiber and matrix treatments delay the creep response and slows the process of creep in flax/vinyl ester composites in the steady state region, respectively.
Also, results of treated flax fiber and one of the novel bio-based resins known as ESS revealed the successful production of bio-composites having properties that meet or exceed those of conventional pultruded members while having 85% bio-content. Moreover, composites using treated flax fiber and ESS resin showed less degradation in properties and appearance after accelerated weathering exposure.
Investigating long-term behavior of treated flax fiber and two more novel biobased resins is currently in progress.