Three-dimensional micromechanics-based constitutive framework for analysisof pultruded composite structures

A new 3D micromechanics-based framework is proposed for the nonlinear analy sis of pultruded fiber-reinforced polymeric composites. The proposed 3D mod eling framework is a nested multiscale approach that explicitly recognizes the response: of the composite systems (layers) within the cross section of the pultruded member. These layers can have reinforcements ii? the form of roving, continuous filament mat (CFM), and/or woven fabrics. Different 3D micromechanical models for the layers can be used to recognize the basic re sponse of the fiber and matrix materials. The framework is implemented with both shell and 3D finite elements. The 3D lamination theory is used to gen erate a homogenized nonlinear effective response for a through-thickness re presentative stacking sequence. The proposed modeling framework for pultrud ed composites is used to predict the stiffness and nonlinear stress-strain response of E-glass/vinylester pultruded materials reinforced with roving a nd CFM. The roving layer is idealized using a 3D nonlinear micromechanics m odel for a unidirectional fiber-reinforced material. A simple nonlinear mic romechanics model for the CE;M layer is also applied. The proposed model sh ows very good predictive capabilities of the overall effective properties a nd the nonlinear response of pultruded composites, based on the in situ mat erial properties, and the volume fractions of the constituents. Experimenta l data from off-axis tests of pultruded plates under uniaxial compression a re used to verify the proposed model. The proposed framework can be easily incorporated within displacement-based finite-element models of composite s tructures.