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This study delves into the effect of repeated low-velocity impacts on the residual tensile strength of composite laminates reinforced with E-glass/epoxy woven fabrics. The specimens underwent a series of low-velocity impacts, each delivering a constant energy of 4 J. Various parameters, such as maximum impact load, displacement, contact time, and absorbed energy, were examined. The residual tensile strength was subsequently analysed for each impact and compared to control specimens that experienced no impact. The results highlighted a significant decrease in residual tensile strength after the initial impact, whereas subsequent impacts exhibited a diminished effect until the puncture of the specimens occurred. [ABSTRACT FROM AUTHOR]

The literature is not abundant with mechanical characterizations of cylindrical shells for civil engineering applications, especially in terms of impact response. In this context, this study intends to evaluate the impact response of cylindrical sandwich shells produced by various types of fibers. Analysis was performed on three alternative configurations: carbon fibers only, carbon fibers and glass, and carbon fibers and basalt. All configurations were tested for static and impact strength. It was concluded that the constituents of the cylindrical sandwich shells are determinants of both static and impact strength. In terms of compressive properties, the lowest displacement (4.4 mm) and highest compressive strength (873 N) and stiffness (354 N/mm) are attributed to configuration 6C. However, the incorporation of basalt fibers decreased these properties to the lowest values, and reductions of 22% and 44% were found for the compressive strength and stiffness, respectively, while the displacement increased by around 66%. On the other hand, in terms of impact, significant benefits were achieved with the introduction of glass fibers. Compared with configurations 6C and 2C+2B+2C, for instance, the elastic recuperation was 25% and 64.6% higher, respectively. [ABSTRACT FROM AUTHOR]

The effect of the interface stiffness and interface strength on the low-velocity impact response of woven-fabric semicylindrical composite shells is studied using finite element (FE) models generated with continuum shell elements and cohesive surfaces. The intralaminar damage is accounted for using the constitutive model provided within the ABAQUS software, while the interlaminar is addressed utilising cohesive surfaces. The results show that the interface stiffness has a negligible effect on the force and energy histories for values between 10 1 N/mm 3 and 2.43 × 10 6 N/mm 3 . However, it has a significant impact on the delamination predictions. It is observed that only the normal interface strength affects the maximum impact force and the delamination predictions. Increasing its value from 15 MPa to 30 MPa resulted in an 8% growth in the maximum force, and a substantial reduction in the delaminated area. The obtained results serve as guidelines for the accurate and efficient computation of delamination. The successful validation of the FE models establishes a solid foundation for further numerical investigations and offers the potential to significantly reduce the time and expenses associated with experimental testing. [ABSTRACT FROM AUTHOR]

This paper presents an efficient and reliable approach to study the low-velocity impact response of woven composite shells using 3D finite element models that account for the physical intralaminar and interlaminar progressive damage. The authors' previous work on the experimental assessment of the effect of thickness on the impact response of semicylindrical composite laminated shells served as the basis for this paper. Therefore, the finite element models were put to the test in comparison to the experimental findings. A good agreement was obtained between the numerical predictions and experimental data for the load and energy histories as well as for the maximum impact load, maximum displacement, and contact time. The use of the mass-scaling technique was successfully implemented, reducing considerably the computing cost of the solutions. The maximum load, maximum displacement, and contact time are negligibly affected by the choice of finite element mesh discretization. However, it has an impact on the initiation and progression of interlaminar damage. Therefore, to accurately compute delamination, its correct definition is of upmost importance. The validation of these finite element models opens the possibility for further numerical studies on of woven composite shells and enables shortening the time and expenses associated with the experimental testing. [ABSTRACT FROM AUTHOR]

Nowadays, due to the complexity and design of many advanced structures, cylindrical shells are starting to have numerous applications. Therefore, the main goal of this work is to study the effect of thickness and the benefits of a carbon composite sandwich cylindrical shell incorporating a cork core, compared to a conventional carbon composite cylindrical shell, in terms of the static and impact performances. For this purpose, static and impact tests were carried out with the samples freely supported on curved edges, while straight edges were bi-supported. A significant effect of the thickness on static properties and impact performance was observed. Compared to thinner shells, the failure load on the static tests increased by 237.9% and stiffness by 217.2% for thicker shells, while the restored energy obtained from the impact tests abruptly increased due to the collapse that occurred for the thinner ones. Regarding the sandwich shells, the incorporation of a cork core proved to be beneficial because it promoted an increase in the restored energy of around 44.8% relative to the conventional composite shell. Finally, when a carbon skin is replaced by a Kevlar one (hybridization effect), an improvement in the restored energy of about 20.8% was found. Therefore, it is possible to conclude that numerous industrial applications can benefit from cylindrical sandwiches incorporating cork, and their hybridization with Kevlar fibres should be especially considered when they are subject to impact loads. This optimized lay-up is suggested because Kevlar fibres fail through a series of small fibril failures, while carbon fibres exhibit a brittle collapse. [ABSTRACT FROM AUTHOR]

Composite laminates subjected to low-velocity impact events on the through-thickness direction are conveniently studied and disseminated in the open literature. However, in terms of laminate cylindrical shells this subject is less common. Therefore, the main goal of the present work is to study the impact response of laminate composite cylindrical shells composed by different type of fibres. For this purpose, laminates with different configurations (6C, 2C+2K+2C and 2C+2G+2C), where the "number" represents the number of layers used and C=Carbon, K=Kevlar and G=Glass fibre layers, were analysed in terms of static and impact strength. It is possible to conclude that both static and impact performance are strongly influenced by the shells' configuration. In terms of compressive static strength, the Kevlar hybrid shells present values 53.2% higher than the 6C shells, while the glass hybrid shells present values 17.3% lower. The impact analyses shows, regardless the similarity of the maximum loads for all configurations, that Kevlar hybrid shells achieved the highest elastic recuperation and the glass hybrid shells the maximum displacement. [ABSTRACT FROM AUTHOR]