Loose fiber molding: Cure and product design fundamentals

The design fundamentals of manufacturing high performance hemp/acrylic composites were explored in this research. The effect of curing temperature and time on the crosslink density and molecular weight between crosslinks of an acrylic resin was evaluated by equilibrium swelling measurements. A kinetics study of the resin was also performed using a differential scanning calorimeter. The 1.4th order model was employed to estimate the kinetics parameters at different heating rates. A unique continuous wetting process was successfully developed for loose natural fiber mats to use for further molding operations.; The effects of various fiber treatments on physical and mechanical properties of the hemp/acrylic composite were investigated; these included treatments such as alkali, amino-silane, and styrene-maleimide resin, as well as Ophiostoma ulmi fungus. Since styrene-maleimide resin treatment resulted in the greatest enhancement of properties compared to the other treatments, additional analyses were performed using inverse gas chromatography and pull-out tests. The results showed that the resin-treated fibers had a slightly higher dispersive force compared to non-treated fibers. Modification of fibers with styrene-maleimide resin slightly decreased the basic character and significantly increased the acid character of hemp fibers. Moreover, the higher interfacial strength for the treated fibers demonstrated that the styrene-maleimide treatment had a beneficial effect on the adhesion of the acrylic resin to hemp fiber.; A detailed study of some thermo-physical properties, including density, heat capacity, and thermal conductivity of the fiber, resin, and composite were performed in order to simulate heat molding of the composite. A non-linear transient heat transfer analysis combined with a cure kinetics model was developed. The temperature and curing behaviour of a flat plate of the composite was predicted using two different numerical methods, a finite difference method and a finite element method. A three-dimensional model was developed for a block of the composite using the finite element method and compared with experimental results. Experimental data showed that the simulation procedure was numerically valid and stable and provided reasonably accurate predictions. Finally, the model was performed for an automotive mirror case to simulate the cure behaviour of a complex structure during compression molding.