I. Adarraga

Hygrothermal effects in composites: Influence of geometry and determination of transverse coefficient of thermal expansion

This work evaluates the influence of geometric properties, the length-to-width ratio, named Aspect Ratio, on curvatures in [θ − 90/θ]T carbon/epoxy composite laminates at room temperature due to thermal residual stresses. A new method to determine experimentally thermal residual curvatures in composites laminates by defining small-length increments on the surface of deformed plate has been exposed. [–454/454]T was considered to obtain a simple analytical expression of twisting curvature. A new way to determine transverse coefficient of thermal expansion α2 is proposed in squared laminates based on experimental values of twisting curvatures of [–454/454]T laminates.

Application of the submodeling technique to the analysis of the edge effects of composite laminates

This study deals with the edge effects in angle-ply composite laminates subjected to tensile test. The submodeling technique is used to achieve the numerical results. In a first step, a [45/–45]s laminated strip is studied, comparing the results with the previous approaches. The fulfilment of equilibrium equations by the stresses obtained numerically is studied to delimit the zone with inaccurate results due to the singularity of the problem. Antisymmetric configurations are analyzed enclosing the validity of the numerical results near the edges to the limits previously obtained. The aspect ratio and the orientation angle have been varied to analyze their effect.

Numerical analysis of displacement and stress fields of off-axis composites in three-point flexure

Three-point flexure test for unidirectional off-axis composites has been analyzed by the finite element method. The main difficulty of modeling three-point flexure test of this kind of material is due to the bending-twisting coupling that induces the lift-off of the specimen at the fixture supports. In the present work, the contact between the load and support rollers and the specimen has been modeled with linear gap elements. The type of element and refinement of the mesh have been analyzed in order to minimize numerical error. After having selected those parameters, a complete model with discretization of load and support rollers has been developed to simulate different test conditions. The numerical displacement field has been compared with analytical and experimental results obtained previously. Furthermore, the length and location of the contact between specimen and rollers has been numerically predicted in some configurations.

Application of the dual integrated force method to the analysis of the off-axis three-point flexure test of unidirectional composites

This paper shows the use of the dual integrated force method in the finite element method and its application to unidirectional composite laminates. This method was developed by SN Patnaik for isotropic materials, considering not only the equilibrium equations but also the compatibility conditions. The method is applied to obtain the stiffness matrix of a four-node rectangular plate element. Then, a three-point flexure test of a unidirectional off-axis composite has been analyzed. The results obtained with this method have been compared with those obtained from a previous analytic approach and with those obtained by commercial software of finite element method, which is based on the stiffness method.