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Abstract: This paper presents a simple analytical model for the prediction of thermo-elastic deformation (spring-in) of angled composite sandwich panels. The development of the model is presented and the simplifying assumptions are clearly defined. Contributions from different mechanisms are clearly shown which gives a good understanding of the problem. The analytical model is validated against a finite element model and the validity of the simplifying assumptions is examined. The agreement between predicted spring-in from the analytical model and the finite element model is very good for the studied sandwich panels with composite skins and varying core materials. The difference in spring-in predictions is less than 0.05° for all cases studied. The simplicity of the model together with the limited number of input parameters makes it a practical tool for composite manufacturing engineers and designers. [Copyright &y& Elsevier]

Process-induced distortions (PID) of high-performance CFRP structures lead to problems with dimensional control if the distortions are not accounted for by compensating the process tool accordingly. There is a need to predict PID via simulation in industry rather than relying on less reliable information such as past experience or measurements on prototype structures. PID are caused by many phenomena, which can make detailed simulation complex and time consuming. This paper presents three simplified techniques for prediction of PID with sufficient accuracy but that are much faster and cheaper to run than traditional complex process models. The three techniques use solid or shell finite elements and use inputs based on measured spring-in of simple L-angles made of the same material and process conditions as the larger scale structures to be simulated. Application of the three techniques to example structures show that the predictions agree well with each other and that they give good predictions compared to experimentally measured distortions of a CFRP box. Given their speed and simplicity they have the potential to be useful for predicting PID for simpler composite structures, particularly early on in the design cycle where quick approximate calculations are of great value to evaluate different design concepts. [ABSTRACT FROM AUTHOR]

Abstract: Background: Excessive stem migration is often problematic after impaction allografting. The mechanisms responsible for migration are not known, but achieving a dense graft bed has traditionally been believed to be essential for stem stability. When the stem is cemented into the allograft bed, however, the graft becomes infiltrated with bone cement. Extensive cement penetration into the graft has been observed in previous studies, resulting in regions of cement–endosteum contact. Methods: This study explored the effects of graft density and cement penetration on stem motion using a finite element model that was validated against experimental data. Findings: Cement penetration has a considerable stabilizing effect on stem motion, whereas graft density is important only when there is no cement–endosteum contact. Stem migration can be attributed primarily to slippage at the endosteum and stem–cement interfaces rather than to shear failure within the graft. Interpretation: Partial cement penetration to the endosteum increases the likelihood of meeting clinical requirements of early implant stability, particularly when a dense graft bed cannot be achieved. [Copyright &y& Elsevier]