Characterization of hybrid composites: Offshore applications

In order to take full advantage of the tailorability of composites, the response of hybrid composites must be understood. In this study hybrid laminates are evaluated experimentally, the in-plane responses of hybrid laminae are investigated analytically, and a method to predict the tensile and bending response of hybrid laminates and the response of filament wound tubes subjected to internal pressure is demonstrated.;The experimental efforts include an examination of the effects of aging in seawater on the tensile and flexural response of hybrid laminates. No degradation due to aging in seawater is detected with environmental scanning electron microscopy. However, evidence of a plasticization of the matrix due to seawater aging is observed in the test data.;The lamina axial tension analysis indicates that the axial failure strains decrease and the axial modulus increases with increases in the ratio of carbon fiber to total fiber volume and the total fiber volume fraction. The interphase modulus and matrix viscoelasticity have a negligible effect on the axial failure strain. Axial failure strains are higher when the different fiber types are intermingled and the axial modulus is constant until failure.;The lamina transverse modulus decreases and the transverse failure strain increases as the ratio of carbon fiber to total fiber volume increases. The lamina shear modulus and failure strain are unaffected by hybridization. The critical factor affecting the transverse and shear failure is the interphase strength when the lamina is perfectly bonded. When the matrix is viscoelastic moisture has no effect on the shear and transverse response at 23;The agreement between the predicted and experimental responses of the hybrid laminates to tensile and bending loads and the tubes to internal pressure is excellent.