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Structural health monitoring (SHM) involves observation and analysis of a system over time using periodically sampled response measurements to monitor the initiation and propagation of a flaw. The article is focused on finite element (FE) modelling of strain field modification induced by flaws in loaded composite structures. Shape of the current production flaw – delamination – was idealised as square with a side of 1 inch. One flaw per laminate in several positions in the layup was considered. The pristine structure was modelled with one element per thickness. For delaminated zone in the centre, the twin coincident elements per thickness were adopted: first element to simulate the lay-up from bottom to delamination, second from delamination to top. The loads and the boundary conditions of the FE model were issued from the tests, based on the ASTM standards: tension test – ASTM D3039, compression after impact test – ASTM D7137 and 4-point bending test – ASTM D7264. Generally, the strain modification is stronger for the delamination near the surface than for the delamination deep in the structure.

Many prey species change their antipredator defence during ontogeny, which may be connected to different potential predators over the life cycle of the prey. To test this hypothesis, we compared reactions of two predator taxa – spiders and birds – to larvae and adults of two invasive true bug species, Oxycarenus hyalinipennis and Oxycarenus lavaterae (Heteroptera: Oxycarenidae) with life‐stage‐specific chemical defence mechanisms. The reactions to larvae and adults of both true bug species strikingly differed between the two predator taxa. The spiders were deterred by the defences of adult bugs, but the larval defences were ineffective against them. By contrast, birds attacked the larvae considerably less often than the adult bugs. The results indicate a predator‐specific ontogenetic change in defence effectiveness of both Oxycarenus species. The change in defence is likely linked to the life‐stage‐specific composition of secretions in both species: whereas secretions of larvae are dominated by unsaturated aldehydes, secretions of adults are rich in terpenoids, which probably serve dual function of defensive chemicals and pheromones. Our results highlight the variation in defence between different life stages and the importance of testing responses of different types of predators. [ABSTRACT FROM AUTHOR]

Bird or hail stone impacts are an important phenomenon that must be taken into consideration when designing aircraft. As engines are the sole thrust-providing mechanisms of an aircraft, it is critical that the effects of bird or hail stone strikes on engine inlets and systems be investigated and mitigated to the greatest extent possible. A combination of experiments and numerical simulations is necessary to properly understand the behaviour of a bird or hail stone during impact and the reaction of the impacted material with the structure. A simulation methodology is developed and validated to certify the bird or hail stone strike resistance of composite air ducts designed for a new generation of jet training aircraft. Physical impact tests were performed on real composite parts. Numerical simulation results were compared with test results. Numerical simulation was also used for test preparation and optimization of the test rig design from the point of view of the influence of the stiffness of the surrounding aircraft structure. The validated modelling procedure allows the analysis of numerous impact scenarios, improving the optimization procedures for aircraft component design and reducing the cost of development by reducing the need to manufacture test prototypes.

Machining of composite materials through classical way, i.e. using conventional tools for turning, drilling, milling, grinding and polishing, produces a lot of very small particles - dust. These particles enter the air, because machining should be performed with a minimum of sprinkling to protect composite material properties and to avoid delamination or swelling. Sometimes, even some burning of epoxide used as binder takes place during machining. Dust produced during machining of the composite material might have negative impact on health and may cause explosion. Skin inflammation or inhalation of the toxic epoxide resin, are some of the examples. Common solution of this problem is suction of particles and fume using machines creating negative pressure. Subsequent removing of these harmful substances from air is quite demanding and expensive. Moreover, using of common suction systems is many times less efficient than declared by producers. This contribution presents a new way of fighting with pollution caused by composite machining. The alternative machining tool for composite machining is abrasive water jet (AWJ). This tool is efficient in all basic machining processes and produces in air only about 1% of dangerous pollution comparing to classical tools. Progress of the AWJ machining system based on robot as a movement device is presented and the first results are commented. The main attention is aimed at machining quality possibilities. However, a part of the contemporary research focused on pollution suppression is also presented in the contribution. [ABSTRACT FROM AUTHOR]

Adults and larvae of a true bug, Scantius aegyptius (Heteroptera: Pyrrhocoridae), closely resemble sympatric firebugs, Pyrrhocoris apterus , and probably form a mimetic relationship with the latter species. Scantius aegyptius adults, although producing a secretion atypical of true bugs, are to some extent chemically protected against predators. In this study, we analysed the composition and function of the larval secretion in S. aegyptius , and investigated the mimetic relationship between larvae of S. aegyptius and P. apterus. The main component of the larval secretion in S. aegyptius is 2-heptanol, a chemical not known to function in anti-predatory defence, followed by (E)-2-octenal, a common defensive chemical of true bugs. When larvae of both species were presented to jumping spiders (Evarcha arcuata), S. aegyptius was slightly less well protected than P. apterus , but the spiders behaved towards the two species in a similar way: they quickly learned to avoid the bugs, but usually attacked them again on the second day. The spiders also generalized their learned avoidance from one true bug species to the other (with only slight asymmetry favouring S. aegyptius), suggesting that the bugs' mimetic relationship is most probably Müllerian, being advantageous to both species. [ABSTRACT FROM AUTHOR]