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Background Total hip replacement has recently followed a progressive evolution towards principles of bone- and soft-tissue-sparing surgery. Regarding femoral implants, different stem designs have been developed as an alternative to conventional stems, and there is a renewed interest towards short versions of uncemented femoral implants. Based on both experimental testing and finite element modeling, the proposed study has been designed to compare the biomechanical properties and clinical performance of the newly introduced short-stem Minima S, for which clinical data are lacking with an older generation stem, the Trilock Bone Preservation Stem with an established performance record in short to midterm follow-up. Methods/design In the experimental study, the transmission of forces as measured by cortical surface-strain distribution in the proximal femur will be evaluated using digital image correlation (DIC), first on the non-implanted femur and then on the implanted stems. Finite element parametric models of the bone, the stem and their interface will be also developed. Finite element predictions of surface strains in implanted composite femurs, after being validated against biomechanical testing measurements, will be used to assist the comparison of the stems by deriving important data on the developed stress and strain fields, which cannot be measured through biomechanical testing. Finally, a prospective randomized comparative clinical study between these two stems will be also conducted to determine (1) their clinical performance up to 2 years’ follow-up using clinical scores and gait analysis (2) stem fixation and remodeling using a detailed radiographic analysis and (3) incidence and types of complications. Discussion Our study would be the first that compares not only the clinical and radiological outcome but also the biomechanical properties of two differently designed femoral implants that are theoretically classified in the same main category of cervico-metaphyseal-diaphyseal short stems. We can hypothesize that even these subtle variations in geometric design between these two stems may create different loading characteristics and thus dissimilar biomechanical behaviors, which in turn could have an influence to their clinical performance. Trial registration International Standard Randomized Controlled Trial Number, ID: ISRCTN10096716 . Retrospectively registered on May 8 2018. Electronic supplementary material The online version of this article (10.1186/s13063-019-3445-x) contains supplementary material, which is available to authorized users.

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Progressive damage modeling (PDM) is a well-established methodology for the prediction of damage initiation and evolution in composite structures. However, as conventional PDM methodology involves a large post-processing procedure, it is impractical for application in large-scale structures due to the high computational cost it requires. In this study, the local character of nonlinearity, due to the scale of the damage topology compared to the size of the entire structure, is exploited to propose proper modifications in the 'classical' PDM methodology. Specifically, the sub-modeling technique principles are combined and integrated in the PDM methodology and the appropriate modifications required are discussed. Furthermore, two damage prediction indices, which are related to the criticality of damage state at specific sub-areas (material layers) of the structure are introduced, in order to achieve significant reductions of the required computational time. Both the improvements make the application of PDM in large-scale composite structures practically feasible; this is demonstrated in the case of a generic composite shear joint whose numerical model comprises over a million degrees of freedom.

A multifield simulation approach of cellular cores produced by additive manufacturing is presented. The analysis is aiming to derive the relation between the manufacturing process parameters and the resulting material failure behaviour. To this purpose, the selective laser melting manufacturing process is initially thermo‐mechanically simulated, followed by the mechanical analysis of the nonlinear core behaviour. The methodology is demonstrated in the case of open‐lattice body‐centred‐cubic (BCC) cellular cores.

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Computational models of structures are widely used to inform decisions about design, maintenance and operational life of engineering infrastructure, including airplanes. Confidence in the predictions from models is provided via validation processes that assess the extent to which predictions represent the real world, where the real world is often characterised by measurements made in experiments of varying sophistication dependent on the importance of the decision that the predictions will inform. There has been steady progress in developing validation processes that compare fields of predictions and measurements in a quantitative manner using the uncertainty in measurements as a basis for assessing the importance of differences between the fields of data. In this case study, three recent advances in a validation process, which was evaluated in an inter-laboratory study 5 years ago, are implemented using a ground-test on a fuselage at the aircraft manufacturer’s site for the first time. The results show that the advances successfully address the issues raised by the inter-laboratory study, that the enhanced validation process can be implemented in an industrial environment on a complex structure, and that the model was an excellent representation of the measurements made using digital image correlation.

One of the most important events during an aircraft's service life is the impact of a bird (ie, bird strike), which could possibly lead to catastrophic failure. According to airworthiness authorities, compliance of an aircraft structure to bird‐strike certification specifications can potentially be proved by simulation. In the present work, combined experimental and numerical investigations are performed, aiming to provide a validated numerical simulation tool for the certification of a composite leading edge structure. To increase the numerical simulation efficiency, the stacked shell approach in the frame of the finite element method is adopted. Comparison of numerical and experimental results shows that the proposed methodology is very promising for the simulation of impact events on complex composite structures. The proposed methodology has been applied for the development of a numerical tool for the simulation of bird strike on a composite leading edge structure.