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From:
Fernanda Mariana Nunes Ravetti and Sérgio Frascino Müller de Almeida, “Post buckling of composite panels subjected to thermal residual stresses”, MSC Software Presentation Number 2007-21, 2007
ABSTRACT: Composite material structures are completely stress free during curing or consolidating process, under high temperatures that vary between 120 deg. C and 400 deg. C. After this process, temperature decreases and material starts to get stiffer. As material physical properties are different in transverse and longitudinal direction, thermal residual stresses appear due to this difference, mainly because of thermal expansion coefficient. Thermal residual stresses effects can be null if the structure is a uniform (not stiffened) square plan panel symmetrically laminated, without external constraints. However, if the panel is reinforced or not symmetrically laminated, the resultant stresses can be not null and affect the panel mechanical behavior. This research studies post-buckling behavior of graphite-epoxy reinforced panels under compression in the presence of thermal residual stresses, considering two different stringer types and three different stringer widths. According to the results found, thermal residual stresses can affect the panel mechanical behavior - depending on type and width of the stringers - increasing stiffness and changing buckling modes, mainly for smaller loads and wider stringers.
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