罗 56. 55. 52. London. New York. tures.Composites Science and Technology,56(9),1001-1015. Huybrechts,S.and Tsai,S.W.1996.Analysis and behavior of grid struc- grid structures.Journal of Composite Materials,30(4),503-534. Chen,H.J.and Tsai,S.W.1996.Analysis and optimum design of composite ymposium,CD-ROM. stiffened geodesic composite structures.Proc.44 International SAMPE Rehfield,L.W.1999.A brief history of analysis methodology for grid- Journal of Mechanical Sciences,46,561-583. ing.Part I:analytical models and minimum weight design.International beams with composite faces and a foam core,loaded in three-point bend- Steeves,C.A.and Fleck,N.A.2004.Collapse mechanisms of sandwich Zenkert,D.1995.An Introduction to Sandwich Construction.Chameleon, tional Journal of Mechanical Sciences,46,585-608. ing.Part II:Experimental investigation and numerical modeling.Interna- beams with composite faces and a foam core,loaded in three-point bend- Steeves,C.A.and Fleck,N.A.2004.Collapse mechanisms of sandwich 兵！：M Vinson,J.R.1999.The Behavior of Sandwich Structures of Isotropic and Composite Sun,C.T.1998.Mechanics of Aircraft Structures.John Wiley Sons,Inc. Principles of Composite Material Mechanics such a way that the current strains depend more strongly on the recent Stress-fime history thannth enough. Behavior is often referred to as"fading memory"because they remember the past in strains depend only on the current stresses.Viscoelastic materials have what memory"because they remember only the unstrained state and the current materials is memory.Perfectly elastic solids are said to have only "simple energy storage.Viscoelastic materials,however,are capable of both storage and dissipation of energy under load.Another characteristic of viscoelastic under load,but not energy dissipation,whereas ideal Newtonian fluids under nonhydrostatic stresses are capable of energy dissipation,but not We know that ideal Hookean elastic solids are capable of energy storage glass transition temperature,TAt temperatures below T however,it will deform just as much,and in the same way if the test time is long temperatures.It will deform like a rubber at temperatures just above the ing at processing temperatures,but is a glassy solid at service(ambient) fluids or solids,depending on the time scale or the temperature.For example,polycarbonate,a thermoplastic polymer,is a liquid during mold- that exhibit characteristics of both viscous fluids and elastic solids.Poly- meric materials,which are known to be viscoelastic,may behave like The word "viscoelastic"has evolved as a way of describing materials needed for the analysis of both viscoelastic and dynamic behavior of com- posites and their constituents. having polymeric constituents.This chapter contains the basic information wave propagation.In addition,many composites exhibit time-dependent viscoelastic behavior under load;this is particularly true for composites ents exhibit time-independent linear elastic behavior.However,composite structures are often subjected to dynamic loading caused by vibration or In the analyses of chapter 1 to chapter 7,it has been assumed that the applied loads are static in nature and that the composite and its constitu- Introduction Analysis of Viscoelastic and Dynamic