http://hdl.handle.net/10016/7182 2013-05-26T06:41:59Z http://hdl.handle.net/10016/16718 Title: Influence of shear plugging in the energy absorbed by thin carbon-fibre laminates subjected to high-velocity impacts Author(s): Buitrago, Brenda L.; García-Castillo, Shirley K.; Barbero, Enrique Abstract: This work examines the energy-absorption process in thin woven laminates made from carbon fibres, with the aim of analysing the energy employed in the formation of a shear plug. This study was conducted with a simplified model which considered five energy-absorption mechanisms. The model was validated with experimental tests and numerical simulations, with regard to the residual velocity of the projectile and perforation velocity. The model makes it possible to evaluate the influence of the shear plugging in laminates of different thickness. It has been demonstrated that this energy-absorption mechanism needs to be considered in the analysis. The main energy-absorption mechanisms for impact at low velocity (i.e. below the perforation velocity) are related to the elastic deformation of fibres and shear plugging, whereas when a higher impact velocity is considered (i.e. above the perforation velocity) such mechanisms are related to the acceleration field of the laminate and the shear plugging. 2012-12-31T23:00:00Z http://hdl.handle.net/10016/15845 Title: Delamination prediction in orthogonal machining of carbon long fiber-reinforced polymer composites Author(s): Santuiste, Carlos; Olmedo, Álvaro; Soldani, Xavier; Miguélez, Henar Abstract: Machining processes of composites are common operations in industry involving elevated risk of damage generation in the workpiece. Long fiber reinforced polymer composites used in high-responsibility applications require safety machining operations guaranteeing workpiece integrity. Modeling techniques would help in the improvement of machining processes definition; however, they are still poorly developed for composites. The aim of this paper is advancing in the prediction of damage mechanisms involved during cutting, including out-of-plane failure causing delamination. Only few works have focused on three-dimensional simulation of cutting; however, this approach is required for accurate reproduction of the complex geometries of tool and workpiece during cutting processes. On the other hand, cohesive interactions have proved its ability to simulate out-of-plane failure of composites under dynamic loads, as impact events. However, this interlaminar interaction has not been used up to date to model out-of-plane failure induced during chip removal. In this paper, both a classical damage model and cohesive interactions are implemented in a three-dimensional model based on finite elements, in order to analyze intralaminar and interlaminar damage generation in the simplified case of orthogonal cutting of carbon LFRP composite. More realistic damage predictions using cohesive interactions were observed. The strong influence of the stacking sequence on interlaminar damage has been demonstrated. 2012-06-30T22:00:00Z http://hdl.handle.net/10016/15787 Title: On the prediction of bolted single-lap composite joints Author(s): Olmedo, Álvaro; Santuiste, Carlos Abstract: A new set of failure criteria to predict composite failure in single lap bolted joints is proposed. The pres ent failure criteria are an extension of Chang Lessard criteria considering a three dimensional stress field and including out of plane failure modes. The advantage with respect to other three dimensional failure criteria is the consideration of non linear shear stress strain relationship. The failure criteria were imple mented in a finite element model and validated through comparison with experiments in literature. Stresses were calculated by a non linear finite element model developed in ABAQUS/Standard which con siders material and geometric nonlinearities. A progressive damage model was implemented in a USDFLD subroutine. The model predicted the effect of secondary bending and tightening torque showing an excel lent agreement with experimental results. Moreover, results were compared with those reported in lit erature using Hashin failure criteria. In addition, a parametric study was carried out to analyse the influence of friction coefficient and tightening torque. 2012-04-30T22:00:00Z http://hdl.handle.net/10016/15786 Title: Out-of-plane failure mechanisms in LFRP composite cutting Author(s): Santuiste, Carlos; Miguélez, Henar; Soldani, Xavier Abstract: LFRP (Long Fiber Reinforced) composites are widely used in structural components for high responsibility applications in different industrial sectors. Composite components are manufactured near final shape, however several machining operations are commonly required to achieve dimensional and assembly specifications. Machining should be carefully carried out in order to avoid workpiece damage. Despite of the interest of numerical modeling to analyze in detail the phenomena involved during composite cutting, there are only few works in the scientific literature dealing with this topic even in the simple case of orthogonal cutting. Out-of-plane failure can be accounted only if three dimensional modeling is performed. However up to date numerical analysis of cutting found in scientific literature was focused in two-dimensional approach. In this paper (2D) and three dimensional (3D) numerical modeling of orthogonal cutting of carbon LFRP composite are presented. The aim of the paper is to analyze the complex aspects involved during cutting, including out-of-plane failure. 2011-09-30T22:00:00Z