Fibre metal laminates (FML) are hybrid materials perspective for wind-turbine, containers and marine objects, besides the aerospace industry. During the manufacturing process some faults can occur and can be hazardous for the reliability of FML structures. One of the most critical defects are kissing bonding due to their lack of detectability and strength compared to traditional delamination defect. The quantitative explanation were under consideration, such as loads effects; material properties; prediction of response; fracture analysis. The purpose of this work is the evaluation the impact of this type of defect on the part in-plane and the out-of-plane mechanical properties. It was presented that even responsive NDT methods are not able to detects the kissing bonding defect in FML components. Simultaneously, the kissing bonding impact on mechanical properties in FML is significant. In the case of FMLs with the orientation of the fibre perpendicular to the peel direction there is one failure pattern which is interlayer fracture. Whereas in the case of FMLs with the direction of the fibres longitudinal to the peel direction two failure patterns occur which is interlayer fracture and translaminar fibre crack. Depending on the kissing bonding area width the interlayer fracture in the composite can be observed until kissing bonding defect area and then transmission of the crack to the metal/composite interface through the fibres. In the case of low extension of poor adhesion area, the two parallel interlaminar cracking can be seen, one at the metal/composite interface in poor adhesion area, the second continuous in the composite layer.

The correct prediction of a composite parts’ final performance is of paramount importance during the initial design phase of the manufacturing process. To this end the correct evaluation of the most effective process parameters and their influence on the parts performance is key for the success of the manufacturing process. Our aim with this paper is to provide methodologies for the prediction of the temperature field in thermoplastic composites during thermoforming and to propose a strategy for process parameter selection. We measured the temperature variations over the different thermoforming stages and compared these values with analytical and finite element results. Our results show the accuracy of the predictions and the importance of the correct laminate temperature with respect to the prediction of the parts’ spring-in angle. We discuss the essential features needed for accurate predictions of the temperature fields over the whole thermoforming process at an early design stage and the potential of a Machine Learning procedure based on Artificial Neural Network to aim for the optimum range of process parameters for a desired part performance outcome. In conclusion, we provide essential guidelines for blank temperature predictions, and the benefit of a machine learning-based tool over traditional approaches.

The quality control of Glare panels manufacturing is an important and complex process including the evaluation of the quality of the basic constituents, namely the aluminium sheets, and the glass fibre reinforced pre-preg. In particular, the handling of aluminium sheets is one of the most critical steps for the manufacturing of Glare laminates. The unintentionally induced deformations, referred to as kinks, can significantly affect the geometry and the mechanical properties of the final laminate. This paper considers the effects of kinks in Glare laminates by developing a comprehensive investigation based on controlled kink manufacturing in aluminium sheets, non-destructive and destructive evaluation of laminates with kinks, and the impact on the compressive ultimate strength. The results contribute to the understanding of the kink induced defects and to define thresholds for improving future automated laminate manufacturing.

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.

During the automated manufacturing of fibre reinforced laminates, defects can be produced. Gaps and overlaps between adjacent prepreg layers can be produced in composites during the tape-layup process. However, the topic is not yet studied for hybrid materials, in which metal sheets and thin prepreg layers lead to different effects due to the defects than in full composites. Here, the effect of gaps and overlaps on the mechanical properties of the Fibre metal laminates (FML) is evaluated. Specimens are manufactured with a specified width of gaps/overlaps and the mechanical performance of the panels is evaluated by some selected mechanical tests. Gaps show to have a considerable effect on the mechanical performance of FML. Compression strength of samples with overlaps was rather increased. Discussions are presented on the influence on each mechanical property according to the severity of the defect (gaps/overlap) and the failure mode(s) under consideration.