Compressive Failure Behaviour of Novel Aramid Fibres

Since the development of the first truly synthetic fibres in the late nineteenth century, scientific efforts have lead to large variety of fibres ranging from fibres for textile applications to high performance fibres used as engineering materials. Examples of high performance fibres that are often used in engineering applications are aramid, glass and carbon fibres. Based on specific tensile properties polymer fibres such as aramids outperform glass and carbon fibres, but a major concern is, however, their behaviour under compressive loading. The work presented in this thesis describes a novel approach to increase the compressive strength of aramid (or PPTA) fibres and to characterise the compressive failure behaviour of these new fibres in more detail. The new concept is based on the addition of PPTA-compatible oligomers containing reactive end-groups. These newly designed oligomers can be considered to act as a molecular ‘glue’ to locally increase lateral cohesion and hence to increase the compressive properties without reducing the axial tensile properties.Fundamentals of Advanced MaterialsAerospace Engineerin

Large area imaging of forensic evidence with MA-XRF

This study introduces the use of macroscopic X-ray fluorescence (MA-XRF) for the detection, classification and imaging of forensic traces over large object areas such as entire pieces of clothing and wall paneling. MA-XRF was sufficiently sensitive and selective to detect human biological traces like blood, semen, saliva, sweat and urine on fabric on the basis of Fe, Zn, K, Cl and Ca elemental signatures. With MA-XRF a new chemical contrast is introduced for human stain detection and this can provide a valuable alternative when the evidence item is challenging for conventional techniques. MA-XRF was also successfully employed for the chemical imaging and classification of gunshot residues (GSR). The full and non-invasive elemental mapping (Pb, Ba, Sr, K and Cl) of intact pieces of clothing allows for a detailed shooting incident reconstruction linking firearms and ammunition to point of impact and providing information on the shooting angle. In high resolution mode MA-XRF can even be used to provide information on the shooting order of different ammunition types. Finally, by using the surface penetration of X-rays we demonstrate that the lead signature of a bullet impact can be easily detected even if covered by multiple layers of wall paint or human blood.(OLD) MSE-