Impact Resistance Of Structures Research Articles

High‐velocity impact resistance of the carbon fiber composite grid sandwich structures

AbstractThe carbon fiber composite grid sandwich structure represents an innovative category of lightweight composite sandwich structures, showcasing remarkable attributes including reduced weight, high‐specific strength, exceptional specific stiffness, and robust design flexibility. Using ABAQUS, the high‐velocity impact performance of carbon fiber composite grid sandwich structure is numerically simulated. This study delved into examining the impact patterns arising from various factors, including the equivalent density, height, and geometric configuration of the core layer. Additionally, the effects of the impact punch's initial velocity, size, and impact position on the high‐speed impact resistance performance of the carbon fiber composite grid sandwich structure were explored. The fracture absorption work of the structure and the kinetic energy attenuation rate of the impact punch are positively correlated with the equivalent density, height of the structural core layer, as well as the initial velocity and dimensions of the impact punch. Notably, the square carbon fiber composite grid sandwich structure was most significantly influenced by the equivalent density of the core layer, while the mixed carbon fiber composite grid sandwich structure was most sensitive to variations in core layer height and punch size. When impacted at the intersection of the ribs, compared with the central position between the two ribs, the structure shows enhanced fracture absorption energy and greater impact kinetic energy attenuation rate.Highlights The structure was modeled based on the interlocking assembly process. The high‐velocity impact resistance of the structure was studied. Different structural parameters were designed for the core layer to study. The initial velocity, size and impact position of the punch were involved.

Scaling laws of low-velocity impact response for RC beams: Impact force and reaction force

Predicting the low-velocity impact response of the prototype based on the scaled test results is one of the significant topics in structural design and protection. Thus, reliable similarity laws are required to bridge the dynamic similarity between models and prototypes. In this study, numerical modeling was carried out by considering plastic damage and strain rate effects. Then, the impact responses of four series reinforced concrete beams satisfying traditional similarity laws were analyzed. The largest beam section size reached 600 mm × 1000 mm. The scaling effects on the impact force profiles (comprising three Types) and reaction force profiles of the beam were investigated. Several characteristic points were defined for the available simplified profiles of impact and reaction forces. It is shown that the scaling effects on each characteristic are not consistent. As the theoretical scale factor increases, the characteristics such as the peak impact force, the positive peak of the reaction force, and its plateau satisfy the traditional similarity law, whereas the characteristics such as the impact force duration and the negative peak of the reaction force do not. Therefore, modified dynamic scale factors for the characteristics of impact and reaction force profiles from models to prototypes were proposed. Based on the suggested scaling laws, the simplified profiles of impact and support reaction forces of the prototype can be predicted. It is expected that it will help researchers to conduct experimental studies and optimized designs on structural impact resistance.

Numerical Analysis of the Impact Resistance of Composite A-Shaped Sandwich Structures.

This paper focuses on the finite element analysis simulation of the impact properties of composite sandwich structures made of carbon fiber-reinforced polymer lamina. In the existing studies, the composite sandwich structures with A-shaped cores have superior mechanical properties under quasi-static plane compression loads compared to W-shaped, Y-shaped, and X-shaped cores. However, there is limited research on the impact resistance of this structure. This paper studied the resistance of a composite A-shaped core structure to ballistic impact. Using ABAQUS/explicit finite element analysis software, ballistic impact tests for the composite A-shaped core structure were simulated based on the Hashin and Yeh failure criteria with a progressive damage model introduced in the user-defined subroutine VUMAT. First, the composite Y-shaped core sandwich structure was verified via experiments and simulations to determine the accuracy of the method, and then the composite A-shaped sandwich structure was subjected to a series of ballistic impact simulations. With varied impact velocity, the damage to the front and rear face sheet and cores via ballistic loads was simulated to illustrate the overall dynamic response process of the sandwich structure. Subsequently, a curve was fitted using a ballistic limit velocity equation, which was used as the criterion to evaluate the impact resistance of the composite A-shaped core structure. The results showed that, under the same relative density and the same number of component layers, the ballistic limit velocity of the composite A-shaped core sandwich structure was bigger than the composite Y-shaped core sandwich structure. The composite A-shaped core structure had 12.23% higher ballistic limit velocity than the composite Y-shaped core, indicating the impact resistance capabilities of the A-shaped core structure. In addition, the impact location's effect on the impact response was investigated.

Effect of Fibres on the Failure Mechanism of Composite Tubes under Low-Velocity Impact.

Filament-wound composite tubular structures are frequently used in transmission systems, pressure vessels, and sports equipment. In this study, the failure mechanism of composite tubes reinforced with different fibres under low-velocity impact (LVI) and the radial residual compression performance of the impacted composite tubes were investigated. Four fibres, including carbon fiber-T800, carbon fiber-T700, basalt fibre, and glass fibre, were used to fabricate the composite tubes by the winding process. The internal matrix/fibre interface of the composite tubes before the LVI and their failure mechanism after the LVI were investigated by scanning electric microscopy and X-ray micro-computed tomography, respectively. The results showed that the composite tubes mainly fractured through the delamination and fibre breakage damage under the impact of 15 J energy. Delamination and localized fibre breakage occur in the glass fibre-reinforced composite (GFRP) and basalt fibre-reinforced composite (BFRP) tubes when subjected to LVI. While fibre breakage damage occurs globally in the carbon fibre-reinforced composite (CFRP) tubes. The GFRP tube showed the best impact resistance among all the tubes investigated. The basalt fibre-reinforced composite (BFRP) tube exhibited the lowest structural impact resistance. The impact resistance of the CFRP-T700 and CFRP-T800 tube differed slightly. The radial residual compression strength (R-RCS) of the BFRP tube is not sensitive to the impact, while that of the GFRP tube is shown to be highly sensitive to the impact.

Experimental investigation on the effect of impact loading on behavior of post- tensioned concrete slabs

Impact resistance of structures has become an essential part of construction projects, especially in mountain zones due to the prominent hazard of falling rocks. Some environmental changes, such as deforestation and modifications in landslides, have increased the danger to civil structures and pose a serious threat to the infrastructure and human life. The effect of impact due to landslide falling rocks on reinforced concrete (RC) slabs has been investigated by many researchers, while very few studied the effect of impact loading on pre-stressed structures. Therefore, the aim of this study is to investigate the behavior of post-tensioned (PT) slabs under impact load. A comparison was made with a traditional (RC) slab having a similar moment capacity. The RC slab was a flat slab with a thickness of 320 mm, while the other two slabs were PT with a thickness of 250 mm. The slabs were subjected to an impact load of 605 Kg dropped freely from 20 m. The load was dropped at the center of gravity for the RC and PT1 slabs. On the other hand, the load was dropped at mid-span of the free edge of the second post-tensioned slab PT2. The tests showed the behavior of the PT slabs under dynamic impact load due to the free falling block, and their different behavior from the RC slab, by comparing displacements, impact force, cracks, and damage type. Also, the results displayed the effect of impact location on the response of PT slabs through analyzing PT1 and PT2 results.