The technical work began with extensive FE modelling to design proper insert definition that was put in the composite plates during manufacturing based on the test plan. Two types of damage defined - manufacturing damage - impact damage). These were simulated and compared with pristine condition. The damage type, size, shape, lay-up position and loading condition were studied in comparison of pristine condition. FE analysis of shear test specimen and element test specimen with inserts were done. The impact damage morphology was under optimisation on the base of first impact tests. For tension, compression and bending specimens, three standard ASTM tests were numerically simulated. Non-standard test was simulated for the shear panel and for the proposed typical aeroplane sub-structure. Static, linear FEM analysis was executed for tension, bending and shear load, linear buckling analysis. However, these analyses were completed with the real impact simulations by the dynamic, non-linear, explicit FEM. Generally, for all tests for both lay-up configuration, the strain modification was more important for the delamination near the surface (near the top or the bottom) than for the delamination deep in the structure. Consequently, the flaw near the surface is much easily detectable than the flaw deep in the structure.
Specimen testing part started with fabrication of composite plates by TM based on the approved test plan. The plates were manufactured and were delivered to VZLU. Specimens were machined from the panels and evaluated by ultrasonic NDT by VZLU. Barely visible impact damage was made using drop a weight machine after specimen extraction to certain specimens. Experiments started by performing of compression tests including strain gages and DIC measurements. Tension tests were done including strain gages and DIC measurements. Two strain gage networks were proposed by VZLU to evaluate changes of the strain field near the flaws. Generally, effect of impact is evident up to 34 mm from impact. None or very low effect was visible on the last strain gage 48 mm far.
Element testing started with fabrication of a beam by TM based on the approved test plan. The beam was delivered to VZLU, machined to proper dimensions, and NDT tested. Element testing started with element tests that were done including a network of strain gage sensors and DIC evaluation. Impact of he element was done afterwards. Testing in compression was done for both samples. Deformation was measured by a network of strain gages and by digital image correlation to evaluate the buckling shape.
Virtual testing started with definition of the subcomponent and the component – flat keel panel for strain analysis during compression loading and curved panel for bending testing. VZLU defined building of FE model of part of real structure including typical structure parts such as skin, stringers, and ribs. Various morphologies of the flaws were modelled to study the relative strain field modification. The location of the flaws were modelled in two locations from skin side. Four cases were analysed. Based on the component definition, the flaws were modelled in two panel locations: at mid bay (flaw no. 1), and on stringer skin coupling internal side (flaw no. 2).
These results were disseminated at the ICEAF, EAN and IWPDF conferences with arciticals and in journals. A functional sample of test equipment for shear testing using a frame was prepared for exploitation. TM benchmarked its SHM software that is ready for exploitation.
