Browsing by Author "Monroy, Aceves C."

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    Design selection methodology for composite structures
    (Elsevier Science B.V., Amsterdam., 2008-01-01T00:00:00Z) Monroy, Aceves C.; Skordos, Alexandros A.; Sutcliffe, Michael P. F.
    This paper presents a methodology to help designers select a shortlist or optimum design of composite structure from a large number of alternatives, taking into account conflicting design objectives or constraints (e.g. weight and cost). The methodology is based on creating a database containing results from an exhaustive search of a wide range of possible solutions. These results can be viewed using a commercial software selection package, originally written for materials selection. The designer then has freedom to change the selection criteria and required design constraints, to allow interactive selection of the data. The design methodology is illustrated by way of a case study, the design of a reinforced dogbone specimen.
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    Drape optimization in woven composites manufacture.
    (2005-07-01T00:00:00Z) Skordos, Alexandros A.; Monroy, Aceves C.; Sutcliffe, Michael P. F.
    This paper addresses the optimisation of forming in manufacturing of composites. A simplified finite element model of draping is developed and implemented. The model incorporates the non-linear shear response of textiles and wrinkling due to buckling of tows. The model is validated against experimental results and it is concluded that it reproduces successfully the most important features of the process. The simple character of the model results in low computational times that allow its use within an optimisation procedure. A genetic algorithm is used to solve the optimisation problem of minimising the wrinkling in the formed component by selecting a suitable holding force distribution. The effect of regularisation is investigated and the L-curve is used to select a regularisation parameter value. Optimised designs resulting from the inversion procedure have significantly lower wrinkling than uniform holding force profiles, while regularisation allows force gradients to be kept relatively low so that suggested process designs are feasible.
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    A simplified rate dependent model of forming and wrinkling of pre-impregnated woven composites
    (Elsevier Science B.V., Amsterdam., 2007-05-01T00:00:00Z) Skordos, Alexandros A.; Monroy, Aceves C.; Sutcliffe, Michael P. F.
    A simplified finite element model is developed and validated for the forming/ draping of pre-impregnated woven composites, incorporating the effects of wrinkling and strain rate dependence. The model development builds upon previous work on simulation of fabric draping using a truss representation of the woven material. Tows are modelled by stiff elastic bar elements, and the non-linear rate dependent shear behaviour is incorporated in elastic-viscoplastic elements that follow an appropriate phenomenological constitutive model. Wrinkling due to tow buckling is simulated by allowing the deactivation of tow elements that undergo compressive deformation. The model convergence is tested and its validity is checked against experimental results from the forming of pre- impregnated woven carbon hemispheres. It is found that the model reproduces successfully experimental measurements of shear and wrinkling with a relative error of approximately 4%, while solution times are kept below 60 s on a conventional PC. These features allow potential iterative use of the model within a process optimisation scheme. The sensitivity of the process outcome to process parameters such as blank holder force and forming speed is investigated.