Composites manufacturing involves many sources of uncertainty associated with material properties variation and boundary conditions variability. In this study, experimental and numerical results concerning the statistical characterization and the influence of inputs variability on the main steps of composites manufacturing including process-induced defects are presented and analysed. Each of the steps of composite manufacturing introduces variability to the subsequent processes, creating strong interdependencies between the process parameters and properties of the final part. The development and implementation of stochastic simulation tools is imperative to quantify process output variabilities and develop optimal process designs in composites manufacturing.

A simplified finite element model is developed and validated for the forming/draping of preimpregnated 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 elasticviscoplastic 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.

The functional design of the campaniform sensillum was modelled as a hole in a plate using twoand three-dimensional finite-element modelling. Different shapes of opening in a fibrous composite plate amplify differently the global strains imposed on the plate, and different configurations of reinforcement also have an effect. In this paper, the main objective is to study the strain and displacement fields associated with circular or elliptical openings in laminated plates in order to investigate their potential for integrated strain sensors. Since we are therefore primarily interested with the detection of displacement, the detailed stress concentration levels associated with these openings are not of primary concern. However, strain energy density levels associated with different hole and fibre configurations have been used to assess the relative likely strength reduction effect of the openings. To compare the relative strain amplification effect of drilled and formed holes of the same size in loaded plates, we have used the relative change in length of diameters (circular) or semi-axes (elliptical) in directions parallel and normal to the load.Various techniques which could sense this deformation were investigated, in particular, the coupling mechanism of a campaniform sensillum of Calliphora vicina. This mechanism was resolved into discrete components: a cap surrounded by a collar, a joint membrane and an annulus-shaped socket septum with a spongy compliant zone. The coupling mechanism is a mechanical linkage which transforms the stimulus into two deformations in different directions: monoaxial transverse compression of the dendritic tip and vertical displacement of the cap. The mechanism is insensitive to change of the material properties of the socket septum, the cuticular cap and the spongy cuticle. The joint membrane may serve as a gap filler. The material properties of the collar have a substantial influence on the coupling mechanism's output. A 30% change of stiffness of the collar causes 45% change in the output of the coupling mechanism. The collar may be able to tune the sensitivity of the sensillum by changing its elastic properties.

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This investigation focuses on nanoparticle filtration in the processing of multiscale carbon and glass fibre composites via resin transfer moulding. Surface modified and unmodified carbon nanotubes (CNTs) were incorporated into a commercial epoxy resin. The dispersion quality was evaluated using electrical measurements of the liquid suspensions. The manufacturing process was adapted to the challenges posed by the modified rheological behaviour of the CNT loaded resin. Nanoparticle filtration was observed; with some of the unmodified systems following so called 'cake filtration' behaviour. This resulted in non linear flow behaviour that deviated from the ideal response observed in RTM filling in conventional composites. The electrical conductivity of relatively high fibre volume fraction multiscale carbon and glass laminates increased by less than an order of magnitude with the addition of the nanotubes.