M. Abouhamzeh

On the prediction of cure-process shape deviations in fibre metal laminates

An investigation of the fabrication-induced distortions in fibre metal laminates is presented using finite-element modelling and experiments. Cooling down is considered as the main source of distortion. Four fibre metal laminate panels are manufactured and their curvature is measured using digital image correlation and linear variable differential transformer. The curvatures are the response of the non-symmetric lay-up to different parameters like stacking order and number of composite or metal layers. Acceptable agreement between model and experiment in predicting the geometry shows that the laminate shape can be predicted with reliability. A large displacement model should be used for large shape deviations in laminates with high level of non-symmetry. Fibre metal laminates may have single or multi-stable configurations after removal from the layup tool. This phenomenon is analysed and parameters and modelling considerations are investigated to obtain a method to predict the final configuration. Further modelling and experimentation are needed to improve the quality of the predictions with increasing complexity of the component.

Detection and Evaluation of Pre-Preg Gaps and Overlaps in Glare Laminates

Gaps and overlaps between pre-preg plies represent common flaws in composite materials that can be introduced easily in an automated fibre placement manufacturing process and are potentially detrimental for the mechanical performances of the final laminates. Whereas gaps and overlaps have been addressed for full composite material, the topic has not been extended to a hybrid composite material such as Glare, a member of the family of Fibre Metal Laminates (FMLs). In this paper/research, the manufacturing, the detection, and the optical evaluation of intraply gaps and overlaps in Glare laminates are investigated. As part of an initial assessment study on the effect of gaps and overlaps on Glare, only the most critical lay-up has been considered. The experimental investigation started with the manufacturing of specimens having gaps and overlaps with different widths, followed by a non-destructive ultrasonic-inspection. An optical evaluation of the gaps and overlaps was performed by means of microscope image analysis of the cross sections of the specimens. The results from the non-destructive evaluations show the effectiveness of the ultrasonic detection of gaps and overlaps both in position, shape, width, and severity. The optical inspections confirm the accuracy of the non-destructive evaluation also adding useful insights about the geometrical features due to the presence of gaps and overlaps in the final Glare laminates. All the results justify the need for a further investigation on the effect of gaps and overlaps on the mechanical properties.