Laminates, analysis

The stiffness ratios (i.e. stiffness of the foam sandwich beam relative to the original solid beam) are also given in Fig. 2.21. In both cases the values given are independent of the original solid material or its dimensions, so this provides a good design chart. The design of solid/foam sandwich structures is also considered in Chapter 3 in the laminate analysis. 

The preceding stress-strain and strain-stress relations are the basis for stiffness and stress analysis of an individual lamina subjected to forces in its own plane. Thus, the relations are indispensable in laminate analysis. 

Obviously, the foregoing description of problems in the mechanics of composite materials is incomplete. Some topics do not fit well within the logical framework just described. Other topics are too advanced for an introductory book, even at the graduate level. Thus, the rest of this chapter is devoted to a brief discussion of some basic lamina and laminate analysis and behavior characteristics that are not included in preceding chapters. 

Fixed arm peel and T-peel test procedures are used to measure peel strength for flexible laminates. Analysis of the contributions from elastic and plastic deformations of the peel arms during these tests enables the energy contribution from plastic effects to be subtracted from the energy required to peel the laminate. In this way, the adhesive fracture toughness is determined. 

Notched laminate analysis predicts the stress state around the hole and evaluates the criticality of these stresses. Stress analyses for notched anisotropic laminates are extensions to the analyses of notched isotropic plates. Specific failure criteria have been... 

CoALA College of Aeronautics Laminate Analysis, Cranfield Institute of Technology (commercial information). 

LAP Laminate Analysis Program, Center for Composite Materials, Imperial College, London (commercial information). 

Laminate Analysis Program (LAP) (1995) Imperial College of Science, Technology and Medicine Anaglyph, London. 

Laminate analysis is based upon the principle of strain compatibility, which means that the in-plane strains in neighbouring layers must be equal. The stresses required in each layer to produce a given strain are first calculated from the previously-computed elastic constants of the layer for the appropriate angle to the fibre direction, and then integrated over all layers. The results define the clastic constants of the whole laminate. Simple computer programs take the drudgery out of these calculations. 

Arrive at values for insertion into computer programs for laminate analysis or finite element analysis... 

At this stage, the strains and curvatures are calculated either by Equations 9.41a and 9.41b or by Equation 9.43 that are known inputs. Once the global deformations are known the individnal ply or lamina deformations can be calculated. Remember that since plane sections remain plane, the laminate analysis assumes that strain is both continuous and linearly distributed on a cross section of the laminate. The result of this is that stress is typically discontinuous due to the different reduced stiffness matrices of adjoining plies. Eor example, since the strain in the x-direction at the interface of plies is assumed to be the same, it follows that stress will be different. The total strain as a function of z is... 

Hint. Think about fundamentals of both lamina and laminate analysis in your result. Actually, it may be best to think how you would not engineer in twist. 

Laminate Analysis Program to Accompany % "Engineering Design with Polymers and Composites" % by J. C. Gerdeen and R. A. L. Rorrer... 

A composite laminate analysis of the coated filament woimd mbing was carried out using a Fortran program. The catheter was treated as a thin walled cylinder composed of fom layers of material as follows. 

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