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365 results on '"Krstulović-Opara, Lovre"'

10. Nondestructive Detection of Osmotic Damage in GFRP Boat Hulls Using Active Infrared Thermography Methods.

Author

Garafulić, Endri, Bagavac, Petra, and Krstulović-Opara, Lovre

Subjects
NONDESTRUCTIVE testing, FOURIER transforms, THERMOGRAPHY, TEST methods, POLYMERS
Abstract

This article presents the application of infrared thermography as a nondestructive testing method (NDT) for detecting osmotic damage in glass-fiber-reinforced polymer (GFRP) and glass-reinforced polymer (GRP) boat hull structures. The aim of the conducted experiments is to explore the possibilities of applying active infrared thermography to real structures and to establish a procedure capable of filtering out anomalies caused by various thermal influences, such as thermal reflections from surrounding objects, geometry effects, and heat flow variations on the observed object. The methods used for post-processing IR signals include lock-in thermography (LT), pulse thermography (PT), pulse phase thermography (PPT), and gradient pulse phase thermography (GT). The practical application and advantages and disadvantages of infrared thermography in identifying osmotic damage in GFRP and GRP boat hulls will be illustrated through three case studies. Each case study is based on specific conditions and characteristics of different types of osmotic damage, enabling a thorough analysis of the effectiveness of the method in detecting and assessing the severity of the damage. The post-processed thermal images enable a clearer distinction between damaged and undamaged zones, improving the robustness of detection under realistic field conditions. [ABSTRACT FROM AUTHOR]

Published
2024
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11. Composites in Ballistic Applications Focused on Ballistic Vests—A Review.

Author

Karhankova, Michaela, Adamek, Milan, Krstulović-Opara, Lovre, Mach, Vaclav, Bagavac, Petra, Stoklasek, Pavel, and Mizera, Ales

Subjects
SYNTHETIC fibers, BODY armor, COMPOSITE materials, FIBROUS composites, NANOSTRUCTURED materials, NATURAL fibers
Abstract

The development of ballistic materials has improved very rapidly in the last few years. Body armor plays an important role in protecting individuals during military threats. Body armor can be divided into hard and soft variants depending on the trade-offs between protection levels and wearer agility. Current research aims to optimize strength-to-weight ratios by using different combinations of synthetic or natural fibers or their combinations to achieve increasingly demanding requirements for ballistic materials. Moreover, it examines the various types of fibers utilized in the construction of body armor, ranging from traditional materials like metal and ceramic to synthetic and natural fibers. This paper discusses ongoing research efforts aimed at further enhancing the performance of these materials, such as the incorporation of modified natural fibers into advanced composite systems. The review provides a comprehensive analysis of the current state of the materials utilized in ballistic protection. [ABSTRACT FROM AUTHOR]

Published
2024
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46. NDT of Composites Based on Active Infrared Thermography and Ultrasound Testing

Author

Krstulović-Opara, Lovre, Bagavac, Petra, Božanić, Antun, and Domazet, Željko

Subjects
non destructive testing, ultrasound testing, infrared thermography, Energy (miscellaneous)
Abstract

Composite materials, such as glass and carbon reinforced ones, are characterized by inhomogeneous structure that requires non destructive testing based on uncommon evaluation methods. The presented approach is based on the active infrared thermography, supported by the A-scan ultrasound testing. The heat wave propagation induced by halogen or xenon bulbs, due to the differences in thermal conductivity, reveals material structure and anomalies. In our previous work we have developed several signal processing and depth evaluation methods, but the real engineering approach requires additional approval testing methods such as the A-scan ultrasound is. The A-scan ultrasound, based on the low frequency probe, enables approval of anomalies located by infrared thermography. The active infrared thermography, as a full field method, enables evaluation of the whole scanned area. The A-scan, as a point-wise method, does not provide the image of whole area of interest. By combining these two methods, robust and reliable approach to analysis of composite structure is enabled.

Published
2021
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48. Development and characterization of aluminum alloy foam - cork hybrid structures

Author

Sousa, João D. P., Pinto, Susana C., Vesenjak, Matej, Carneiro, Vitor H., Krstulović-Opara, Lovre, Marques, Paula A. P., and Duarte, Isabel

Subjects
Hybrid structures, Manufacturing, Characterization, Aluminium alloy foam, Cork
Abstract

Cellular solids and porous materials have been considered as one of the most suitable lightweight multifunctional materials for a wide range of commercial and industrial applications, e.g. in medicine, military. Their use contributes to an immediate and significant weight reduction and material savings of the components but also to multifunctionality due to their 3D cellular structures (open-cells or closedcells). Herein, hybrid structures based on cellular materials are developed and studied by combining open-cell aluminum foam with cork. These hybrid structures were prepared by infiltrating a mixture containing polymer-coated cork powders into the open-cell foam. The samples are geometrically analyzed using X-ray microcomputed tomography to extract morphological and topological properties of the voids and the solid phase. The mechanical, thermal, acoustic, and fire retardancy properties of these aluminum foam-cork hybrid structures are evaluated and compared with their individual components (open-cell aluminum alloy foam and agglomerated cork). published

Published
2022

49. Development and characterization of in-situ sandwich panels with aluminum alloy foam core

Author

Caldeira, Ana Sofia, Vesenjak, Matej, Carneiro, Vitor H., Krstulović-Opara, Lovre, and Duarte, Isabel

Subjects
Three-point bending, In-situ sandwich panels, Aluminium alloy foam
Abstract

The aluminum alloy foams have been explored to be used in energy absorption applications that require lightweight structures with high strength-to-weight and stiffness-to-weight ratios, high impact energy absorbing capacity, and good damping of noise and vibration. The metal foams are usually applied as core and/or as filler of sandwich panels and thin-walled structures. The purpose of this paper is to develop in-situ sandwich panels consisting of a highly porous aluminum foam core and aluminum alloy face sheets manufactured by the powder metallurgy method in which the face sheets are bonded to the foam core during the foam formation. The samples are geometrically analyzed in 2D and 3D using X-ray microcomputed tomography to extract morphological and topological properties of the foam core, the face sheets, and the bonding between them. The mechanical and acoustic properties of in-situ sandwich panels are evaluated. published

Published
2022

50. Bending behavior of triply periodic minimal surface foam-filled tubes.

Author

Novak, Nejc, Al-Ketan, Oraib, Krstulović-Opara, Lovre, Rowshan, Reza, Vesenjak, Matej, and Ren, Zoran

Subjects
MINIMAL surfaces, FOAM, TUBES, SPECIFIC gravity, TUBE bending
Abstract

Foam-filled tubes represent one of the best energy-absorbing components for future crashworthiness applications. Triply Periodic Minimal Surface (TPMS)-filled tubes were investigated under quasi-static and dynamic three-point bending loading conditions. The TPMS-filled tubes enhanced specific energy absorption up to 46% compared to the sum of empty tubes and the core response separately. The validated computational models were used to extend the computational study to investigate graded core of TPMS-filled tubes under bending loading. The study results show that the mechanical response of TPMS-filled tubes can be tuned using different relative densities or/and distributions of relative density of the core. [ABSTRACT FROM AUTHOR]

Published
2023
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