Postbuckling and failure characteristics of selected flat rectangular graphite-epoxy plates loaded in compression

Abstract

Results o f an experimental study o f t h e postbuckling response and f a i l u r e c h a r a c t e r i s t i c s o f 16-and 24-ply o u a s i -i s o t r o p i c and 24-ply o r t h o t r o p i c f l a t rectangular graohite-epoxy p l a t e s loaded i n compression a r e presented. The r a t i o o f f a i l u r e load t o b u c k l i n g load was higher f o r specimens w i t h lower i n i t i a l b u c k l i n g s t r a i n s than f o r specimens w i t h higher i n i t i a l b u c k l i n g s t r a i n s . Some specimens supported more than f i v e times t h e i r i n i t i a l buckling l o a d b e f o r e f a i l i n g . A n a l y t i c a l r e s u l t s obtained from a nonlinear general s h e l l analysis computer code c o r r e l a t e we1 1 w i t h t e s t r e s u l t s up t o f a i l u r e . The specimens f a i l e d along a nodal l i n e o f t h e b u c k l i n o mode i n an induced shear f a i l u r e mode. Some specimens e i t h e r had c i r c u l a r holes o r were subjected t o low-speed impact damage before t e s t i n g . The postbuckling s t r e n g t h o f specimens w i t h high i n i t i a l buckling s t r a i n s i s degraded more by holes and imoact damage than soecimens w i t h lower i n i t i a l b u c k l i n q s t r a i n s . I n t r o d u c t i o n Current metal a i r c r a f t design p r a c t i c e a1 lows some s t r u c t u r a l comoonents (e.g., fuselage and s t a b i l i z e r panels) t o buckle p r i o r t o f a i l u r e under c e r t a i n loading conditions. These components a r e desioned t o c a r r y t h e i r u l t i m a t e load w h i l e i n a postbuckled s t a t e . The use o f advanced-composite m a t e r i a l s i n s i m i l a r postbuckl i n g appl i c a t i o n s could lead t o e f f i c i e n t s t r u c t u r a l designs. Before comp o s i t e s t r u c t u r a l components can be designed f o r these a p p l i c a t i o n s , however, t h e i r postbuckling response and f a i l u r e c h a r a c t e r i s t i c s must be understood w e l l enough t o p r e d i c t t h e i r s t r u c t u r a l behavior. E a r l i e r published work on t h e postbuckl i n g behavior o f composite s t r u c t u r e s (e.g., Refs. 1-4) has focused on a n a l y t i c a l s o l u t i o n s o f c l a s s i c a l o r t h o t r o p i c p l a t e problems. Only a l i m i t e d amount o f data has been published comparing t e s t r e s u l t s w i t h a n a l y t i c a l p r e d i c t i o n s . The compressive s t r e n g t h o f b u c k l i n g -r e s i s t a n t graphiteepoxy laminates has been shown t o be s e r i o u s l y degraded by c i r c u l a r holes (Refs. 5-7) and low-speed impact damage (Refs. 5 , 8 and 9). On t h e o t h e r hand, p r e l iminary t e s t s on graphite-epoxy laminates (Ref. 7) i n d i c a t e t h a t c i r c u l a r holes may have l i t t l e o r no e f f e c t on b u c k l i n g response o r postb u c k l i n g strength. This paper presents r e s u l t s o f a t e s t program t o study the postbuckling response and f a i l u r e c h a r a c t e r i s t i c s o f s...

Progressive damage of laminated cylindrical/conical panels under meridional compression

“…An attempt is made to validate the formulation with geometric nonlinearity and evolving damage by comparing the present results with the available experimental results of Starnes and Rouse (1981) for two laminated CCSS flat panels [Panel I: (±45 /0 2 /±45 /0 2 / ±45 /0 /90 ) S ; a ¼ 50.8 cm, b ¼ 17.8 cm, h ¼ 3.36 mm, and Panel II: (±45 /0 /90 ) 3S; a ¼ 50.8 cm, b ¼ 14.0 cm, h ¼ 3.36 mm] with initial imperfection under uniaxial compression with material properties…”

“…For evaluating the damage parameters J 22 and k h , in-plane shear strain at failure point and shear stress versus strain curve are required (Barbero and de Vivo, 2001) in addition to strength properties given by Starnes and Rouse (1981). The values of parameters J 22 ¼ 0.357046 Â 10 À13 and k h ¼ 2.65 Â 10 À8 are assumed such that the predicted failure load is close to the experimental value for Panel I.…”

Nonlinear Formulations of a Four-Node Quasi-Conforming Shell Element

“…The boundary conditions were: at x = 0,178, W 0 = X 0 = 0, at y = 0, U 0 = W 0 = X 0 = dW/dx = 0, at y = 508, W 0 = X 0 = dW/dx = 0, U 0 = constant. The analytical buckling load and critical end shortening from [147] is 40 kN and 0.5 mm, respectively. The panel is modelled using XSHELL41 elements, 12 along the width and 24 along the height.…”

“…16 × 16 elements were used to model both problems and the results are shown with the analytical solution provided by Zhang[181] and the FE solution from XSHELL81[81]. While the general trends of the results are the same as those given by Zhang, the curve panel solutions tend to give higher buckling loads.C4/Graphite-Epoxy Panel Under In-plane CompressiveLoading Starnes and Rouse[147] conducted experimental studies on the post buckling and failure characteristics of a C4/graphite-epoxy panel, T300/5208. The panel consists of 24 plies, (±45/0 2 / ± 45/0 2 / ± 45/0/90) s , and is 508 mm high, 178 mm wide and 3.36 mm thick.…”

Coupled buckling and postbuckling analysis of active laminated piezoelectric composite plates

“…Thus, the buckling of composite structures and their ability to carry loads beyond the critical point into the postbuckling range has received substantial analytical and experimental attention. For example, we mention the reviews of Leissa (1987) and Chia (1988), the models for unsymmetric plates by Jensen and Lagace (1988), the early experimental work by Starnes and Rouse (1981), the analytical work by Engelstad et al (1992) on postbuckling response and failure modes of panels loaded in compression, and the recent works on dynamic instability (Tabiei and Simitses, 1997), thermomechanical buckling , and the buckling of sandwich structures (Kardomateas et al, 2002;Librescu and Hause, 2000).…”