SMARTFIBER: enabling cost-effective, miniaturized structural health-monitoring of composite structures

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Experimental study of the high strain rate shear behaviour of Ti6Al4V

Three different high strain rate shear test techniques are applied on the titanium alloy Ti6Al4V. Two techniques for testing of bulk materials and one technique for sheet materials are used: torsion of thin-walled tubes, compression of hat-shaped specimens and tension of planar shear specimens. The tests are carried out on respectively torsion, compression and tensile split Hopkinson bar setups. Although shear stresses dominate the stress state in these three tests, the local stress state and its distribution and evolution are different. Therefore, the three techniques are considered to be rather complementary than equivalent tests. In this work, the value of the three test techniques for material characterization is evaluated. Where possible, digital image correlation (DIC) is used to clarify the test results. In addition, parameters difficult to assess experimentally are estimated through finite element simulations of the three tests

Flexible PCL tube scaffolds by winding of micro-extruded filaments

An important requirement for tissue engineering scaffolds is matching of the functional me-chanical properties to their natural tissue counterpart. Specifically for arteries this comprises the elastic re-sponse of the vessel wall to blood pressure. Human aorta has a low elastic modulus when compared to some FDA-approved synthetic polymer materials frequently used in tissue engineering. The current research en-deavours to expand the existing production technology of 3D plotting to winding of micro-extruded filaments in order to obtain flexible polymer tubes with continuous fibre. Tube scaffolds are manufactured by conven-tional 3D plotting and by winding. Their structure and quasi-static mechanical properties are evaluated and compared to human aorta. Winded tubes are found to be far more suitable for application as a blood vessel scaffold than their 3D plotted counterparts

Influence of the geometry of hat-shaped specimens on the formation of adiabatic shear bands

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Dynamic mode-I delamination of composite laminates using a drop-weight tower and optical data-acquisition

Impact events can hardly be called quasi-static. To test for relevant properties with quasi-static test methods thus seems to make little sense, especially when materials with a rate-sensitivity are the subject of testing. Therefore, a test setup is developed to obtain the trac-tion-separation behaviour and fracture toughness of composites in mode I delamination at impact rates of deformation. An optical technique is applied to obtain the load-deflection curve, allowing for contactless measurements

Fusion bonding of carbon fabric reinforced polyphenylene sulphide

In recent years, there is a growing interest in joining techniques for thermoplastic composites as an alternative to adhesive bonding. In this manuscript, a fusion bonding process called hot-tool welding is investigated for this purpose and the used material is a carbon fabric reinforced polyphenylene sulphide. The quality of the welds is experimentally assessed using a short three-point bending setup, which has an interesting distribution of interlaminar shear stresses. It can be concluded that although the hot-tool welding process shows high short-beam strengths, it has some drawbacks. Therefore, a design of an infrared welding setup is presented

Numerical study of the influence of the specimen geometry on split Hopkinson bar tensile test results

Finite element simulations of high strain rate tensile experiments oil sheet materials using different specimen geometries are presented. The simulations component ail experimental study, using a split Hopkinson tensile bar set-up, Coupled with a. full-field deformation measurement, device. The simulations give detailed information on the stress state. Due to the small size of the specimens and the way they are connected to the test device, non-axial stresses develop during loading. These stress components, are commonly neglected, but, as will be shown, have a distinct influence on the specimen behaviour and the stress-strain curve extracted from the experiment. The validity; of the basic assumptions of Hopkinson experiments is investigated: the uniaxiality of the stress state, the homogencity of the strain and the negligibleness of the deformation of the transition zones. The influence, of deviations from these assumptions on the material behaviour from a Hopkinson experiment is discussed