Michael Aldridge

The influence of the representative volume element (RVE) size on the homogenized response of cured fiber composites

The influence of the representative volume element (RVE) size (in terms of fiber packing and number of fibers for a given fiber-volume fraction) on the residual stresses created during the curing process of a continuous fiber-reinforced polymer matrix tow is investigated with the ultimate goal of finding a minimum unit cell size that can be used later for a homogenization procedure to calculate the response of woven fiber textile composites and in particular, fiber tows. A novel network curing model for the solidification of epoxy is used to model the curing process. The model takes into account heat conduction, cure kinetics and the creation of networks in a continuously shape changing body. The model is applied to the curing of a fiber/matrix RVE. The results for the minimum size of the RVE, obtained on the basis of the curing problem, are compared with a similar RVE, modeled as an elastic-plastic solid subjected to external loads, in order to compare the minimum RVE sizes obtained on the basis of different boundary value problem solutions. (Some figures may appear in colour only in the online journal)

Combined Experimental and Simulation Study of the Cure Kinetics of DCPD

The cure kinetics of dicyclopentadiene was investigated using a combination of inelastic light scattering measurements and molecular-scale simulations. Concurrent Brillouin and Raman scattering served to monitor the structural evolution of the curing network as a function of time, both in terms of network connectivity and the concentration of chemical species present. Density functional theory calculations were used to interpret the measured Raman spectra. Comparison of the measured elastic moduli as a function of the degree of cure with those of structures generated using reactive molecular dynamics simulations provide insight into the reaction mechanism. An unexpected dependence of the reaction rate on the catalyst concentration was found.

Integrated computational materials science and engineering of textile polymer composites

An integrated computational framework for textile polymer composites is introduced. A novel polymer curing model is used in connection with modeling the manufacturing process of textile composites. The model is based on the notion of polymer networks that are continuously formed in a body of changing shape due to changes in temperature, chemistry and external loads. Nonlinear material behavior is incorporated through nonlocal continuum damage mechanics that preserves mesh objectivity in calculations that go beyond maximum loads. The integrated model is applied to the curing of plain weave textile composites made from carbon ber tows and Epon862 resin. The mechanical and chemical properties are measured during curing using concurrent Brillouin and Raman light scattering. It is shown that signi cant stresses can develop during cure. The e ect of these stresses on the manufactured part performance, when subsequent service loads are applied, is evaluated and a reduction in ultimate load, in agreement with experimental observations, is observed.