The early impact behaviour of single and multi-ply Kevlar
® 129 fabric armour systems is investigated using an explicit finite element code, TEXIM, developed in-house. This numerical model is ...carefully validated using continuous temporal data obtained from an instrumented experimental setup. The model is then used to explore the loss in ballistic efficiency of woven fabric targets, as experienced early in the impact event, when either the number of layers in the panel or the yarn denier is increased.
Glass and carbon fiber composite laminates were made by vacuum infusion of vinyl ester resin into biaxially knitted glass and carbon fiber fabrics. The strengths of the glass and carbon fiber ...specimens in tension, compression, open hole tension, open hole compression, transverse tension, indentation and ballistic impact were compared. The carbon fiber laminates proved mechanically superior under loading conditions where the strength is mainly fiber dominated, i.e. under tensile loading and indentation. The ratio of the carbon fiber laminate strength to the glass fiber laminate strength, for laminates of equal thickness, was similar to the ratio of the fiber tensile strengths. The glass fiber laminates were equally strong or stronger under loading conditions where the strength is mainly resin dominated, i.e. compressive loading and ballistic impact. In the carbon fiber specimens, the failure was in general more localized and the strengths had more scatter than in the glass fiber specimens.
This paper provides a description of a simple and cost-effective continuous measurement system for impact. Originally developed at Johns Hopkins university for use in flyer plate impact experiments, ...the measurement system has been enhanced for the continuous, non-contact measurement of projectile displacement during ballistic impact events. A sheet of laser light is progressively blocked and unblocked by the projectile, and the corresponding change in total intensity is measured and converted to a displacement–time curve. Through the use of simple mathematical operations, the system can be used to determine the time histories of projectile velocity and acceleration, impact force and projectile energy loss during an impact event. While this technique can be applied to a wide range of engineering materials, this paper presents examples of measurement results for impact of composite and textile targets.
Electrospun nonwovens have great potential for biomedical applications. They can be used, for example, to mimic the structure of the extracellular matrix of biological tissue. In this work, it is ...demonstrated that the surface properties of nanofiber nonwovens made of biocompatible and very slowly biodegrading polyamide can be modified by UV picosecond laser processing. Basically, the nanofiber structure is only slightly changed by the corresponding laser process. Significant laser‐induced material change occurs only along narrow lines determined by the scanning process. The newly formed surface structures resemble a bulk surface. It is shown that the growth of mammalian chondrocyte cells (SW1353) is initially more effective on the laser‐processed surface. Cell growth occurs preferably along the laser‐generated lines. After several days of cell growth, an extended layer of cells is formed over the laser‐modified and unmodified surface sections. Thus, laser‐based surface modification provides another tool to affect cell proliferation on polyamide nanofiber nonwovens.
Due to their outstanding properties and their similarity to extracellular matrix (ECM), electrospun nonwovens have great potential for biomedical applications. In this work, surface structuring of electrospun Polyamide 6 nanofiber nonwovens by laser ablation is reported. The influence of the surface topography on the proliferation of human chondrosarcoma cells (SW1353) is demonstrated.
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