Slide 1

Slide 2 Hygrothermal behavior of composite laminates Composite materials can absorb moisture and expand in the same way that they expand due to temperature. We can use the same kind of analysis to deal with stresses that arise from both. In this course we will focus on thermal behavior. The effect of temperatures on composite laminates is more pronounced than on metals because of large disparity in coefficient of thermal expansion. Slide 3 Effect of mismatch Slide 4 Thermal deformations If ply can expand or contract due to hygrothermal effects, only strains, but no stresses. Stress free expansion strain in a unidirectional layer (Fig. 3.2) Slide 5 Strains and stresses Free strains Hookes law when total strains are different from free strains. Slide 6 Interaction between plies 0/90/45 laminate Constraining effect of adjacent laminates Slide 7 (0/90) s laminate Stress-free expansion of layers Constrained deformation Slide 8 Residual strains Slide 9 Residual stresses Slide 10 Thermal loads If a laminate is subjected to temperature change without any loads then the stress and moment resultants should be zero. Substituting from previous slide for in-plane equation for symmetric laminate Loads needed to produce same strains without temperatures Slide 11 Thermal loads for a single isotropic layer Slide 12 With bending Slide 13 With Tsai-Pagano Material constants Thermal loads Thermal material constants Any checks that we can apply?