In Situ Computed Tomography—Analysis of a Single-Lap Shear Test with Clinch Points

As lightweight design gains more and more attention, time and cost-efficient joining methods such as clinching are becoming more popular. A clinch point’s quality is usually determined by ex situ destructive analyses such as microsectioning. However, these methods do not yield the detection of phenomena occurring during loading such as elastic deformations and cracks that close after unloading. Alternatively, in situ computed tomography (in situ CT) can be used to investigate the loading process of clinch points. In this paper, a method for in situ CT analysis of a single-lap shear test with clinched metal sheets is presented at the example of a clinched joint with two 2 mm thick aluminum sheets. Furthermore, the potential of this method to validate numerical simulations is shown. Since the sheets’ surfaces are locally in contact with each other, the interface between both aluminum sheets and therefore the exact contour of the joining partners is difficult to identify in CT analyses. To compensate for this, the application of copper varnish between the sheets is investigated. The best in situ CT results are achieved with both sheets treated. It showed that with this treatment, in situ CT is suitable to properly observe the three-dimensional deformation behavior and to identify the failure modes.

MEJORA DE LAS PROPIEDADES MECÁNICAS DE UN SISTEMA COMPUESTO CEMENTICIO MEDIANTE EL USO DE UN TEJIDO DE SISAL DISEÑADO

En los últimos años, los materiales compuestos FRCM (fabric-reinforced cementitious matrix composites) producidos con tejidos de fibras naturales se han convertido en potenciales sustitutos de sistemas compuestos de fibras sintéticas o minerales. La eficiencia de los materiales compuestos FRCM depende, entre otras cosas, de su capacidad de adherencia y transmisión de los esfuerzos internos entre sus componentes. En esta investigación se diseñó un sistema frcm cementicio reforzado con tejidos de sisal para que alcance niveles satisfactorios de adherencia y resistencia. Para mejorar sus propiedades mecánicas y obtener un sistema adecuado para el reforzamiento de elementos de hormigón armado, fue necesario el diseño y fabricación de tejidos de sisal de características geométricas particulares, favorables a la penetrabilidad. El comportamiento mecánico del sistema FRCM diseñado en este estudio se verificó llevando a cabo pruebas de corte SLS (Single Lap Shear test) y pruebas pull-off. Los resultados se compararon con aquellos obtenidos probando materiales compuestos FRCM producidos con tejidos no diseñados de sisal.

Influence of Filler Amount and Content on the Mechanical Performance of Joints Bonded with Metal Powder Filled Adhesive

The objective of this study is to investigate the surface roughness that effect the capability of adhesive with adding aluminium powder and 63/37 Sn-Pb soft solder powder to the epoxy to increase the mechanical strength of joints. The adhesive strength of the joints was determined by utilizing the single-lap shear test. As seen from the experiments, the surface roughness has an important effect on the strength of adhesive bonded joints. Experimental results show that joints prepared by adhesive which was modified, adding in the amount of 5 wt% 63/37 Sn-Pb powder have more mechanical strength than joints compared to one which is prepared by adding aluminium powder with different ratios as 5, 25,50 wt%.