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A demand raised is how to improve the survivability of aircraft and naval structures concerning low- and high-velocity impacts. Since fundamental failure is due to mainly by fracture, a fundamental understanding of both mechanisms...
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A demand raised is how to improve the survivability of aircraft and naval structures concerning low- and high-velocity impacts. Since fundamental failure is due to mainly by fracture, a fundamental understanding of both mechanisms and mechanics of the material is crucial. It is important to understand the deformation and damage mechanisms involved in the impact to improve the design of composite structures. Several approaches have been exploited to improve the impact damage resistance of composite laminates in different conditions. Among these, the development of composite laminates stacking different fibres in the same matrix results very interestingly. This paper deals to investigate on the high and low speed impact performance of hybrid composite configurations made of glass/carbon and basalt fibres. Low-velocity impact at penetration and high speed tests at different impact velocity were carried out at the room and low temperatures to evaluate the goodness of hybridization proposed and the temperature effect on the composite performances. Among the three proposals, a hybrid basalt carbon configuration was identified as the best both at low speeds and at high impact speeds for both temperatures tested.
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? 2022 Elsevier LtdThis paper is devoted to Reinforced Concrete (RC) beams that can be subjected to accidental falls of substantial masses (hard impacts at low velocities), such as the beams of bridges, industrial buildings, or fa...
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? 2022 Elsevier LtdThis paper is devoted to Reinforced Concrete (RC) beams that can be subjected to accidental falls of substantial masses (hard impacts at low velocities), such as the beams of bridges, industrial buildings, or factories. Here the reference is to existing RC beams, which have no purposely designed reinforcement to resist impacts. The paper focuses on a mass that falls around the midspan, where the capacity of a RC beam to resist an impact is minimum, due to a potential primary cracking pattern that consists of vertical cracks. The impact here is defined by the combination of the mass that falls down and its velocity at the impact. The paper provides an analytical formulation to predict the combinations that trigger the collapse of a RC beam (i.e., ultimate combinations). After having framed the research question, the paper presents the two possible failure modes, the derivation of the equations, the sensitivity of the bearing capacity to the main parameters, comparisons with existing results from literature, and two applications, whose results are discussed.
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This paper presents an investigation into the damage characteristics and failure strengths of composite laminates at low velocity impact tests. Three E-glass fabrics, non-crimp fabric, woven fabric, and nonwoven mat, were selected...
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This paper presents an investigation into the damage characteristics and failure strengths of composite laminates at low velocity impact tests. Three E-glass fabrics, non-crimp fabric, woven fabric, and nonwoven mat, were selected as reinforcements for the composite laminates. Impact tests were conducted using a guided drop-weight test rig in ascending energy to 24 J/layer nominal impact energy. Metallographic microscopy was used to observe the damage characteristics of the perpendicular cross-section of the impacted laminates after a micropowder polishing treatment. When the load-time and the energy-time histories were compared with the fractographics, it was found that fiber breakage had occurred prior to the major damage. When the impact energy increased over the threshold energy of the major damage, matrix cracking, delamination, and fiber breakage were observed at the back surface, below a nearly undamaged zone, which were attributed to the bending stresses.
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Composite laminates are increasingly being used in more complex structural applications where edges and cut outs are inevitable. These applications include wing skins of military and civil aircraft, further aerospace applications ...
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Composite laminates are increasingly being used in more complex structural applications where edges and cut outs are inevitable. These applications include wing skins of military and civil aircraft, further aerospace applications as well as automotive panels and critical structures. Parts of composite structures are particularly vulnerable to impacts, including near the edge of an inspection port or other aperture. Furthermore, impacts to such areas may be to the edge of the laminate rather than the surface. The research described here includes both experimental investigations and finite element simulations of impact damage on the plane of the laminate but near the edge (near-edge), and on the edge (on-edge) of composite laminates. The damage size and mechanisms have been explored. The results demonstrate the vulnerability of composite laminates to on-edge impact.
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Shape memory alloy (SMA) materials possess complete superelasticity or pseudoelasticity above the austenite finish temperature (A(f)) and many unique mechanical, thermal, thermal-mechanical and electrical properties compared with ...
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Shape memory alloy (SMA) materials possess complete superelasticity or pseudoelasticity above the austenite finish temperature (A(f)) and many unique mechanical, thermal, thermal-mechanical and electrical properties compared with other conventional materials. Many studies have reported that the superelastic and hysteresis properties of SMA materials can absorb energies coming from external excitations or sudden impacts. In addition, due to the special electrical properties of NiTi superelastic wires, they can also be used as a strain-sensing element to monitor structural health conditions. In this paper, composite laminated specimens embedded with SMA wire sensors were fabricated and a detailed testing system was designed, for example for multi-parameter measuring for impact and weak signal processing for SMA sensors. A low-velocity impact test shows that SMA wire sensors embedded in fibre-reinforced plastic (FRP) laminate can be used to monitor impact responses, such as the location of impact damage, impact degree, and strain distribution. Experimental results and theoretical predictions reveal almost the same results. Compared with other methods, the research provides a simple, economic and reliable technique for monitoring important engineering structures online.
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This experimental study addresses the effect of ceramic reinforcement on the impact performance of functionally graded (FG) circular plates. The FG circular plates were produced from two different ceramic (SiC or A1_2O_3) and meta...
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This experimental study addresses the effect of ceramic reinforcement on the impact performance of functionally graded (FG) circular plates. The FG circular plates were produced from two different ceramic (SiC or A1_2O_3) and metal (Al) combinations using powder stacking-hot pressing technique. The Al/SiC FG circular plates exhibited better impact resistance than A1/A1_2O_3 FG circular plates. The effect of ceramic particle size was also investigated on the impact performance of specimens with different composition variations. A ceramic particle size of 50 μm improved the impact performance. In addition, the material composition and impactor velocity also affected the impact performance. Thus, the contact force increases as the composition changes from metal-rich to ceramic-rich. The peak contact force increases with increasing the velocity of impactor.
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Impact and compression after impact characteristics of a typical plain weave fabric E-glass/epoxy composite have been studied for plates with different thicknesses and the same incident impact energy. Impact studies have been carr...
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Impact and compression after impact characteristics of a typical plain weave fabric E-glass/epoxy composite have been studied for plates with different thicknesses and the same incident impact energy. Impact studies have been carried out on an instrumented drop weight impact test apparatus. Post-impact compressive strength has been obtained using NASA 1142 test fixture. Compressive strength of an unnotched specimen has been obtained using Lockheed test fixture with modified specimen geometry. Power fits for peak contact force and maximum plate displacement have been given as a function of plate thickness. It is observed that the impact damage area has quasi-lemniscate shape. Further, damage mechanism has been studied during the post-impact compressive testing. The residual compressive strength as a function of a plate thickness has been obtained.
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The present paper investigates interfacial delamination in a GLARE fibre metal laminate having a central circular hole under multiple low-velocity impacts (LVIs) by cylindrical impactors. A full 3D finite element (FE) formulation ...
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The present paper investigates interfacial delamination in a GLARE fibre metal laminate having a central circular hole under multiple low-velocity impacts (LVIs) by cylindrical impactors. A full 3D finite element (FE) formulation is developed for analysing the response of GLARE under multiple cylindrical impacts using Hertzian contact law, and Newmark-beta method is used for transient dynamic solution. Stresses and strains obtained from the FE analysis are used to assess the interfacial delamination. Influence of important parameters like length and radius of impactor, order of occurrence and location of impact on the extent of delamination have been studied. Results from the present analysis indicate that the outer aluminium thickness and impact interval between the successive impacts greatly influence the magnitude of contact force as well as delamination at the fibre-metal interfaces which initiates at free edges along the periphery of the hole.
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An analytical model is developed to predict the impact characteristic parameters of composite cylindrical shells when low-velocity penetration and non-penetration damage are considered. The critical impact velocity criterion for j...
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An analytical model is developed to predict the impact characteristic parameters of composite cylindrical shells when low-velocity penetration and non-penetration damage are considered. The critical impact velocity criterion for judging the penetrating failure of such structures is also proposed. The impact contact force, displacement, and load-displacement curve of the structure subjected to oblique non-penetrating impact loading are solved using the improved Hertz contact theory, cumulative damage theory, stiffness degradation method, etc. Based on the formula derivation of critical impact velocity, the key impact parameters are solved, such as the residual velocity of the projectile and damage area of the structure with penetrating impact, which takes into account three energy absorption mechanisms, such as delamination, laminating crushing and linear momentum transfer. A series of non-penetrating and penetrating impact tests are conducted using a low-velocity drop hammer rig and a light gas gun. The prediction results of the proposed model are compared to both experimental and literature results. One can find out that the largest prediction errors of the peaks of impact contact force and displacement deformation are 12.3 and 9.2 %, respectively, and the counterparts of residual velocity and damage area are 12.0 and 6.2 %, respectively. Hence, the present model is trustworthy for predicting these impact parameters. Moreover, it is advised to adopt an appropriate stacking sequence, a high ratio of structural thickness to radius, a large oblique impact angle of the projectile, and a small mass ratio of the projectile to such a structure to enhance its impact resistance or reduce impact response. In addition, it is worth noting that the current model probably has a big prediction error of the high-velocity impact behaviors involving the material heating and soft effects caused by penetration damage since high strain rate and temperature effects are not considered.
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