FORMING OF POLYMER MATRIX COMPOSITES : A FINITE ELEMENT APPROACH

Abstract

Fields like aerospace and automobiles are always in need of lighter materials with good strength. Conventional materials do not satisfy these requirements. Many structural parts used in aerospace and automobile field are of complex shapes which can be manufactured by forming processes. Therefore use of polymer matrix composites having light weight with good process ability, in these fields is increasing. For forming of polymer matrix composites it is important to understand the effect of different design and processing parameters on formability of polymer matrix composites The present dissertation work illustrates finite element modeling and analysis of formability of polymer matrix composite. As thermal and explicit dynamic analysis cannot be done in single analysis, thermal-explicit sequential analysis technique has been used for thermoforming analysis of composite plate. Composite sheet having glass fibers reinforced in polypropylene matrix has been modeled using Plane-55 elements for thermal analysis and Plane-162 element for explicit dynamic analysis. Parameters used for investigation are fiber volume fraction, bend radius, punch velocity and fiber material. Influence of these parameters has been investigated with respect to Von-Mises stresses and plastic strain developed during bending. Results show that increase in fiber volume fraction in composite sheet causes decrease in formability of polymer matrix composite. Stresses developed during forming are less for 30% fiber volume fraction as compared to 20% and 40% fiber volume fractions. But formability is higher for lower fiber volume fraction that is 20%. An increase in the bend radius causes formability of polymer matrix composite to increase. Formability of polymer matrix composite does not linearly depend upon forming velocity. Up to some velocity increase, formability of composite increases, after that if velocity further increased formability reduces. For polymer matrix composite having 30% fiber volume fraction, 500mm/min forming velocity gives maximum formability. Polymer matrix composite reinforced with carbon fibers produces more stresses as compared to those with glass fiber reinforced. Therefore formability is more for glass fiber reinforced polymer matrix composites as compared to those with cabon fiber reinforced.