Optimization of a Composite Laminate

Let s consider one rather restricted structural optimization problem, that of a composite laminate. You have seen claimed as attractive advantages of composite structures the fact that we can orient the laminae in a laminate to our heart s content to try to get the most efficient structure. This characteristic is totally unlike what is possible with metal structures. This laminate orientation flexibility is certainly an advantage, but how do we use it  

Let s start by reviewing quantitatively the analysis and design process for metal plates. For an isotropic metal plate under extensional loading, only, the load is related to the strains by 

from the lateral force condition that Ny = 0, 

for a prescribed allowable strain, we can solve for the plate thickness necessary to avoid failure (without consideration of a factor of safety)  

Note that different thicknesses result from Equation (7.14) for different materials with their characteristic values of E and eauov abie- s, the design problem has only one answer if the material is specified, but many answers exist if the material is not specified. 

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