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This study investigates the impact resistance of performance-based geopolymer concrete beams through drop-weight impact tests. Three ordinary portland cement (OPC) beams and 12 geopolymer concrete (GC) beams were tested, considering several research factors, such as concrete strength, longitudinal reinforcement ratio, stirrup ratio, and drop height. The experimental findings indicate that increasing the longitudinal reinforcement ratio or stirrup ratio within a certain range can effectively mitigate damage and deformation in GC beams subjected to impact loading. Furthermore, an increase in strength was observed to result in decreased midspan and residual displacement, while a deflection prediction formula with high accuracy and low dispersion was developed for designing impact-resistant GC beams with an error of no more than 5.5%. Lastly, a dynamic damage criterion for GC beams is proposed to assess their damage under impact loading. [ABSTRACT FROM AUTHOR]

The effectiveness of repair work relies on whether the interface substrate can achieve sufficient bond strength when subjected to numerous stresses. This study investigated the bond properties of repaired normal concrete (NC-to-NC) elements, including cube, beam, and U-shaped specimens, after undergoing natural fracture due to flexural and tensile stresses. The specimens were repaired using a polyurethane (PU) matrix by gluing the two parts and applying compression, splitting, and drop-weight impact (DWI) tests to evaluate the bond strength properties. The results revealed that the PU matrix effectively repairs NC substrate with adequate bond strength, which exceeds the minimum allowable bond strength specified in the ASTM ACI 546-06 to rehabilitate damage concrete structures. The reference beams exhibit a peak applied load capacity of 15.6 kN with less deflection than the repaired samples. The compressive strength of the NC-to-NC repaired specimens loaded along and parallel to the interface plane revealed a decrease in compressive strength of 47.3% and 31.5% compared to the NC-R samples, respectively. The mean number of blows at the cracking stages appeared nearly equal for reference and repaired NC-to-NC specimens. The reference specimens exhibited an average number of 24 and 31 blows at the initial and failure stages, respectively, which were higher by 9.1% and 5.2% than the NC-to-NC repaired specimens. The PU binder showed promising results in achieving adequate interfacial bond strength under static and impact loads. [ABSTRACT FROM AUTHOR]

In this research, two distinct designs of protective structures were developed to address structural damage caused by ships impacting the internal structures of floating docks during maintenance operations. The designed protective structures consist of support sections and load-bearing sections, with the load-bearing section comprising three frame sections. For ease of description, the front frame section, middle frame section, and rear frame section are referred to as Frame A, Frame B, and Frame C, respectively. A drop-weight test was conducted with a stern-shaped indenter impacting the structures at 3.89 m/s. This study also assessed varying impact speeds and positions. The results showed that Specimen 2 had localized indentations on Frame B, while Specimen 1 exhibited overall deformation of Frame B and additional deformations in Frame A. The simulations agreed with the experimental results, confirming the model's accuracy. At speeds from 2.34 m/s to 5.45 m/s, Specimen 2 consistently showed localized deformations, while Specimen 1 showed comprehensive deformation of Frame B at 3.89 m/s due to lower rigidity. When the indenter impacted the specimens at different locations with a speed of 5.45 m/s, the two specimens exhibited varying degrees of damage. As the impact location shifted from the central area to the end, the maximum indentation depth of Specimen 1 decreased from 52.26 mm to 41.71 mm, while that of Specimen 2 decreased from 43.26 mm to 38.50 mm. The reduction in indentation depth and extent as the impact location approached the support frame can be attributed to the increasing involvement of the web plate beneath the frame in resisting the impact. Additionally, compared to Specimen 1, Specimen 2 exhibited a relatively smaller overall indentation depth, and the impact of location variation on indentation depth was also relatively minor. [ABSTRACT FROM AUTHOR]

This study addresses the inherent brittleness of ultra-high-performance fiber re-inforced concrete (UHPFRC) by introducing a U-shaped specimen and investigating the impact strength of U-shaped UHPFRC retrofitted with polyurethane (PU) grout overlays. A drop-weight impact test was conducted on the U-shaped specimens utilizing a 2.1 kg weight. Various PU overlay thicknesses (5 mm, 10 mm, and 15 mm) were applied to the specimens. Machine learning techniques, specifically artificial neural networks (ANN) and support vector regression (SVR) were utilized to analyze the experimental data. Results indicate that UHPFRC cast with PU grout overlaid exhibit decrease in flexural strength compare to reference specimens. On the other hand, significance improvement in impact resistance were observed, with overlaid thickness. The addition of 5 mm, 10 mm, and 15 mm PU grout layers substantially improved the first crack strength of UHPFRC-5PU, UHPFRC-10PU, and UHPFRC-15PU specimens by 94 %, 340.3 %, and 600 %, respectively, compared to UHPFRC-0PU. Machine learning models accurately predicted failure crack strength (N2), with ANN and SVR achieving determination correlation (R2) values of 0.9838 and 0.9816 during the training and testing phases, respectively.

The effectiveness of repair work relies on whether the interface substrate can achieve sufficient bond strength when subjected to numerous stresses. This study investigated the bond properties of repaired normal concrete (NC-to-NC) elements, including cube, beam, and U-shaped specimens, after undergoing natural fracture due to flexural and tensile stresses. The specimens were repaired using a polyurethane (PU) matrix by gluing the two parts and applying compression, splitting, and drop-weight impact (DWI) tests to evaluate the bond strength properties. The results revealed that the PU matrix effectively repairs NC substrate with adequate bond strength, which exceeds the minimum allowable bond strength specified in the ASTM ACI 546-06 to rehabilitate damage concrete structures. The reference beams exhibit a peak applied load capacity of 15.6 kN with less deflection than the repaired samples. The compressive strength of the NC-to-NC repaired specimens loaded along and parallel to the interface plane revealed a decrease in compressive strength of 47.3% and 31.5% compared to the NC-R samples, respectively. The mean number of blows at the cracking stages appeared nearly equal for reference and repaired NC-to-NC specimens. The reference specimens exhibited an average number of 24 and 31 blows at the initial and failure stages, respectively, which were higher by 9.1% and 5.2% than the NC-to-NC repaired specimens. The PU binder showed promising results in achieving adequate interfacial bond strength under static and impact loads.

In this research, two distinct designs of protective structures were developed to address structural damage caused by ships impacting the internal structures of floating docks during maintenance operations. The designed protective structures consist of support sections and load-bearing sections, with the load-bearing section comprising three frame sections. For ease of description, the front frame section, middle frame section, and rear frame section are referred to as Frame A, Frame B, and Frame C, respectively. A drop-weight test was conducted with a stern-shaped indenter impacting the structures at 3.89 m/s. This study also assessed varying impact speeds and positions. The results showed that Specimen 2 had localized indentations on Frame B, while Specimen 1 exhibited overall deformation of Frame B and additional deformations in Frame A. The simulations agreed with the experimental results, confirming the model’s accuracy. At speeds from 2.34 m/s to 5.45 m/s, Specimen 2 consistently showed localized deformations, while Specimen 1 showed comprehensive deformation of Frame B at 3.89 m/s due to lower rigidity. When the indenter impacted the specimens at different locations with a speed of 5.45 m/s, the two specimens exhibited varying degrees of damage. As the impact location shifted from the central area to the end, the maximum indentation depth of Specimen 1 decreased from 52.26 mm to 41.71 mm, while that of Specimen 2 decreased from 43.26 mm to 38.50 mm. The reduction in indentation depth and extent as the impact location approached the support frame can be attributed to the increasing involvement of the web plate beneath the frame in resisting the impact. Additionally, compared to Specimen 1, Specimen 2 exhibited a relatively smaller overall indentation depth, and the impact of location variation on indentation depth was also relatively minor.

This study investigated the impact strength of U-shaped polyurethane (PU)-modified concrete using repeated drop-weight impact tests. A U-shaped specimen was introduced in this study to modify the testing procedure of the ACI 544-2R committee for the drop-weight impact test aiming to minimize the scatter result of this testing method. The static characteristics and impact resistance of U-shaped PU-modified concrete were subjected to repeated weight drops of 0.877 kg. The effects of PU binder on the mechanical and impact strength performance were evaluated in four groups of PU-modified concrete containing 0%, 10%, 20%, and 30% prepared to produce normal concrete-polyurethane (NC-PU) specimens. Machine learning (ML) techniques, which include artificial neural network (ANN) and support vector regression (SVR), were employed to train and test the experimental dataset. The result showed that PU binders significantly decrease mechanical behavior and improve concrete impact strength. At the optimal content, flexural strength was increased by 3.6%, and the compressive strength of the control specimen (NC-PU0) was 49.17% higher than the concrete containing 20% PU (NC-PU2) specimen. The U-shaped specimens reduce the scatter result of repeated drop-weight impact test results suggested by the ACI 544-2R testing method. Adding 10% PU and 20% PU binder improved the first crack strength of NC-PU1, NC-PU2, and NC-PU3 by 685.71%, 1528.6%, and 157% compared to the NC-PU0 specimen. The machine learning techniques accurately predict the N2. ANN and SVR demonstrate a strong relationship between the experimental N2 and predicted N2 with determination correlation (R2) values of 0.9944 and 0.9981 at the training and testing phase, respectively. [ABSTRACT FROM AUTHOR]

In this paper, the individual and synergistic effects of silanized‐multiwalled carbon nanotubes (S‐MWCNTs) and silanized‐Titanium dioxide (S‐TiO2) nanoparticles on the drop‐weight impact response of Kevlar fiber‐reinforced epoxy (KE‐EP) composites were evaluated. In the first step, the nanofillers were functionalized using an amino organosilane coupling agent (3‐Aminopropyltrimetoxysilane [APTMS]). Next, multiscale composites were prepared by adding 0.3 wt% S‐MWCNTs, 1 wt% S‐TiO2, and 0.3 wt% S‐MWCNTs + 1 wt% S‐TiO2 in the matrix. The samples were exposed to drop‐weight impact at various impact energies of 15, 30, and 45 J. The findings demonstrated that the sample filled with 0.3 wt% S‐MWCNTs + 1 wt% S‐TiO2 had the best impact performance, regardless of the initial impact energy. When compared to the neat KE‐EP sample, the multiscale composite filled with 0.3 wt% S‐MWCNTs + 1 wt% S‐TiO2 had greater peak force and absorbed energy by 23% and 18%, respectively under 45 J impact energy. Analysis of the fracture surfaces illustrated a good interfacial bonding between the Kevlar fibers and matrix for the multiscale composite having hybrid nanofillers. [ABSTRACT FROM AUTHOR]

Deck structures subjected to drop-weight low-velocity impact are critical safety elements for ships and offshore structures. Therefore, the aim of the present study is to propose experimental research on dynamic responses of deck structures composed of stiffened plates subjected to drop-weight impact of a wedge impactor. The first step was to fabricate a conventional stiffened plate specimen and a strengthened stiffened plate specimen, as well as a drop-weight impact tower. Then, drop-weight impact tests were carried out. Test results show that local deformation and fracture occurred in the impact area. A sharp wedge impactor caused premature fracture, even under relative low impact energy; the permanent lateral deformation of the stiffened plate was reduced by 20–26% by the strengthening effect of a strengthening stiffer; residual stress and the stress concentration of the cross-joint caused by welding may cause undesired brittle fracture. The present investigation provides useful insight for improving the crashworthiness design of the deck structure of ships and offshore structures. [ABSTRACT FROM AUTHOR]

Macrofibers have often been used to increase the tensile strength, durability, crack resistance, spalling, impact resistance, and toughness of concrete. However, the impact behavior of fiber-reinforced concrete (FRC) structures is quite different from their static behavior, and the effectiveness of macrofibers in improving impact resistance should be carefully evaluated. In this study, the impact behavior of FRC with polypropylene (PP) macrofibers was studied through a series of drop-weight impact tests. First, the material characteristics of the FRC with PP fibers under static conditions were evaluated. Test specimens were constructed and drop-weight impact tests were performed. The main parameters were the presence or absence of PP fibers and the drop height, which is related to the magnitude of the impact energy. From the results, it can be found that the crack width of the FRC specimen was smaller than the normal concrete specimen for a similar residual deflection after the impact test due to the bridging effect of the macrofibers. However, the effect of PP fibers on the impact resistance was not significant, even though there was a considerable increase in tensile and flexural performance under static conditions, since the hardening effect after the sharp reduction in strength shown in the static test of FRC is not effective in the impact test. [ABSTRACT FROM AUTHOR]

Porous concrete is an energy absorption material, which has been widely used in civil engineering, traffic engineering and disaster reduction engineering. However, the effect of pore structure on the impact behavior of the porous concrete is lacked. In this study, a series of drop-weight impact tests were carried out on three typical types of porous concrete, i.e., concrete hollow brick (CHB), autoclaved aerated concrete (AAC) and foamed concrete (FC), to investigate the effect of pore structures on their impact behavior. For comparison, static load tests were also conducted as references. According to the damage to the samples, the developments of impact force, strain, contact stress–strain relationship and absorbed energy during drop-weight during the impact test were measured and analyzed. The results show that the ratio between the peak impact stress and compressive strength of CHB was 0.44, while that of AAC and FC increased to about 0.6, indicating that the small and uniform pore structure in AAC and FC had a higher resistance against impact load than the hollow cavity of CHB. In addition, the elastic recovery strain in AAC increased by about 0.2% and its strain at peak contact stress increased by about 160% for a comparison of CHB, implying that a small open pore structure could enhance ductility. Besides, the peak contact stress of FC was close to that of AAC during impact loading, while the strain at peak contact stress of FC increased by about 36% compared with AAC, revealing that the closed-pore structure could further enhance the deformation potential. Correspondingly, the energy absorption rates of CHB, AAC and FC were 85.9 kJ/s, 54.4 kJ/s and 49.7 kJ/s, respectively, where AAC decreased by about 58% compared with CHB, and FC decreased by about 10% compared with AAC. [ABSTRACT FROM AUTHOR]

This paper presents the experimental, statistical modeling, and reliability analysis of impact resistance of micro steel fiber reinforced concrete (FRC) incorporated with nano silica (NS) using a drop‐weight impact test. U‐shaped concrete specimens were developed for the experimental work. The result showed that the combined effect of micro steel fiber (SF) and NS led to significant improvement of impact resistance of concrete mixtures, and lower ductility ratios were obtained for specimens with high SF and NS content. A common failure pattern was observed for all the concrete specimens. The response surface methodology models developed to predict the impact resistance of FRC‐NS mixtures showed a high degree of correlation. Due to the variation in the drop‐weight impact test' result, the Weibull distribution (WD) function was employed for advance analysis, and the result revealed that the probabilistic distribution of first crack strength (N1) and failure strength (N2) follows the two‐parameter WD. [ABSTRACT FROM AUTHOR]

Deck structures subjected to drop-weight low-velocity impact are critical safety elements for ships and offshore structures. Therefore, the aim of the present study is to propose experimental research on dynamic responses of deck structures composed of stiffened plates subjected to drop-weight impact of a wedge impactor. The first step was to fabricate a conventional stiffened plate specimen and a strengthened stiffened plate specimen, as well as a drop-weight impact tower. Then, drop-weight impact tests were carried out. Test results show that local deformation and fracture occurred in the impact area. A sharp wedge impactor caused premature fracture, even under relative low impact energy; the permanent lateral deformation of the stiffened plate was reduced by 20–26% by the strengthening effect of a strengthening stiffer; residual stress and the stress concentration of the cross-joint caused by welding may cause undesired brittle fracture. The present investigation provides useful insight for improving the crashworthiness design of the deck structure of ships and offshore structures.

This study demonstrates that the impact energy absorption capabilities of flexible sheets can be significantly enhanced by implementing tessellated designs into their structure. Configurations of three tessellated geometries were tested; they included a triangular-based, a rectangular-based, and a novel square-based pattern. Due to their geometrical complexity, multiple configurations of these tessellations were printed from a rubber-like material using an inkjet printer with two different thicknesses (2 and 4 mm), and their ability to absorb impact energy was compared to an unpatterned inkjet-printed sheet. In addition, the effect of multi-sheets stacking was also tested. Due to the tailored structure, the impact testing showed that the single-layer sheets were more effective at absorbing impact loads, and experience less deformation, than their two-layer counterparts. The 4 mm thick tessellated patterns were most effective at absorbing impact loads; all three thick patterns measured about 40% lower impact forces transferred to the base of the samples compared to the unpatterned counterparts. [ABSTRACT FROM AUTHOR]

Macrofibers have often been used to increase the tensile strength, durability, crack resistance, spalling, impact resistance, and toughness of concrete. However, the impact behavior of fiber-reinforced concrete (FRC) structures is quite different from their static behavior, and the effectiveness of macrofibers in improving impact resistance should be carefully evaluated. In this study, the impact behavior of FRC with polypropylene (PP) macrofibers was studied through a series of drop-weight impact tests. First, the material characteristics of the FRC with PP fibers under static conditions were evaluated. Test specimens were constructed and drop-weight impact tests were performed. The main parameters were the presence or absence of PP fibers and the drop height, which is related to the magnitude of the impact energy. From the results, it can be found that the crack width of the FRC specimen was smaller than the normal concrete specimen for a similar residual deflection after the impact test due to the bridging effect of the macrofibers. However, the effect of PP fibers on the impact resistance was not significant, even though there was a considerable increase in tensile and flexural performance under static conditions, since the hardening effect after the sharp reduction in strength shown in the static test of FRC is not effective in the impact test.

In this work, the compressive residual strength tests results, Compression After Impact (CAI), are presented. The specimens were made of carbon-epoxy prepreg E722-02 UHS 130-14. Two variants of specimens were tested: samples undamaged and samples with damage that was centrally introduced by a drop-weight impact, as per the ASTM D7136/7136M standard. An impactor with potential energy equal to 15J and the type of support required by the standard were used. The size of impacted damages, defined as an area of damage on a plane perpendicular to the impact direction, and the equivalent diameter were specified using the flash thermography method.

Porous concrete is an energy absorption material, which has been widely used in civil engineering, traffic engineering and disaster reduction engineering. However, the effect of pore structure on the impact behavior of the porous concrete is lacked. In this study, a series of drop-weight impact tests were carried out on three typical types of porous concrete, i.e., concrete hollow brick (CHB), autoclaved aerated concrete (AAC) and foamed concrete (FC), to investigate the effect of pore structures on their impact behavior. For comparison, static load tests were also conducted as references. According to the damage to the samples, the developments of impact force, strain, contact stress–strain relationship and absorbed energy during drop-weight during the impact test were measured and analyzed. The results show that the ratio between the peak impact stress and compressive strength of CHB was 0.44, while that of AAC and FC increased to about 0.6, indicating that the small and uniform pore structure in AAC and FC had a higher resistance against impact load than the hollow cavity of CHB. In addition, the elastic recovery strain in AAC increased by about 0.2% and its strain at peak contact stress increased by about 160% for a comparison of CHB, implying that a small open pore structure could enhance ductility. Besides, the peak contact stress of FC was close to that of AAC during impact loading, while the strain at peak contact stress of FC increased by about 36% compared with AAC, revealing that the closed-pore structure could further enhance the deformation potential. Correspondingly, the energy absorption rates of CHB, AAC and FC were 85.9 kJ/s, 54.4 kJ/s and 49.7 kJ/s, respectively, where AAC decreased by about 58% compared with CHB, and FC decreased by about 10% compared with AAC.

There is an ever-increasing demand in the automotive sector to continuously improve the performance and reduce cost through weight reduction in the structure of the vehicle. In the present scenario, it is also necessary to meet the standards set by crash safety regulating authorities in various parts of the world. In automobiles, the crash box is placed in the anterior region to absorb the impact energy in the event of an accident. Glass fiber reinforced plastic crash boxes have a high strength-to-weight ratio and also are good in energy absorption, particularly useful in this scenario. In this paper, the effectiveness of different triggers in combination with various geometries is investigated for Glass fiber reinforced plastic crash boxes using drop-weight impact testing. A trigger is a geometric irregularity introduced in the crash box design to alter the energy as well as force levels by modifying the deformation mode under loading. Comparison of change in force level, absorption of impact energy, specific energy absorption values was performed for composite crash boxes made of various types of cross-sectional geometries along with multiple patterns of triggers. Force versus displacement (F–D) curves are drawn for all the cases of the glass fiber reinforced plastic crash boxes to understand the behavior of each combination formed with various types of geometries and triggers, under impact loading. Strength-to-weight ratio was considered as the deciding factor for the comparisons to know the best and worst cases of the crash boxes made of different cross-sections along with various trigger types. This study provides detailed insights into the drop-weight impact testing procedure including the preparation of specimens, setting up the drop-weight impact test, preparation of specimen clamps, safety precautions involved, data acquisition from the test and its processing. [ABSTRACT FROM AUTHOR]

Acrylonitrile butadiene styrene (ABS) is a tough material, which is used for engineering purposes (e.g. covers of electronic and engine parts). On the other hand, styrene acrylonitrile (SAN) is a brittle transparent material with good optical properties, it is used for household items, such as bowls and boxes in refrigerator. Both of these materials can be loaded by impact forces, for example fall of the item on the floor. In this study the influence of fall height on ABS and SAN samples under drop-weight impact test is tested. After the test, failures are evaluated as well as maximum impact force and all consumed work, which was used for the deformation and the failure of the material. [ABSTRACT FROM AUTHOR]

Abstract: To study crack dynamic propagation behaviour and rock dynamic fracture toughness, a single cleavage triangle (SCT) specimen was proposed in this paper. By using these specimens and a drop‐weight test system, impact experiments were conducted, and the crack propagation velocity and the fracture time were measured by using crack propagation gauges. To examine the effectiveness of the SCT specimen and to predict the test results, finite difference numerical models were established by using AUTODYN code, and the simulation results showed that the crack propagation path agrees with the test results, and crack arrest phenomena could happen. Meanwhile, by using these numerical models, the crack dynamic propagation mechanism was investigated. Finite element code ABAQUS was applied in the calculation of crack dynamic stress intensity factors (SIFs) based on specimen dimension and the loading curves measured, and the curves of crack dynamic SIFs versus time were obtained. The fracture toughness (including initiation toughness and propagation toughness) was determined according to the fracture time and crack speeds measured by crack propagation gauges. The results show that the SCT specimen is applicable to the study of crack dynamic propagation behaviour and fracture toughness, and in the process of crack propagation, the propagation toughness decreases with crack propagation velocity, and the crack arrest phenomena could happen. The critical SIF of an arrest crack (or arrest toughness) was higher than the crack propagation toughness but was lower than the initiation toughness. [ABSTRACT FROM AUTHOR]

This study investigates the impact behavior of fiber-metal laminates (FMLs) (Carbon FMLs and Glass FMLs), which were fabricated by using high-stiffness steel, carbon prepreg, and glass prepreg through autoclave molding. The mechanical behavior of the FMLs was evaluated by performing tensile, compressive, in-plane shear, and low-velocity impact tests. Drop-weight impact tests were conducted to induce cracking of the FMLs, and the crack initiation along with crack propagation behavior of the different laminate sequences ([0/0], [0/90], [0/90/0], [90/0/90] and [0/90/90/0]) were also studied. The results show that the fabricated FMLs have higher strength and stiffness than conventional FMLs. Their impact strengths increased, and weights decreased simultaneously. The absorption energy was proportional to the crack length that was induced by the low-velocity impact. Moreover, it was found that the fiber orientation mainly affected the direction of crack propagation in the FMLs. This investigation facilitates the design of high-stiffness and lightweight FMLs for automotive parts. [ABSTRACT FROM AUTHOR]

Three-point bending tests on notched beams of three types of steel fiber-reinforced self-compacting concrete (SFRSCC) have been performed by using both a servo-hydraulic machine and a drop-weight impact instrument. The lo ading rates had a range of six orders of magnitude from 2.20 × 10-3 mm/s (quasi-static) to 2.66 × 10³ mm/s. These SFRSCCs had the same matrix, but various types of steel fiber (straight and hooked-end) and contents (volume ratios), 0.51%, 0.77% and 1.23%, respectively. The results demonstrate that the fracture energy and the flexural strength increase as the loading rate increases. Moreover, such tendency is relatively moderate at low rates. However, at high rates it is accentuated. For the 0.51% fiber content, the dynamic increase factors of the flexural strength and the fracture energy are approximately 6 and 3, while for the 1.23% fiber content, they are around 4 and 2, respectively. Thus, the higher the fiber content the less rate sensitivity there is. [ABSTRACT FROM AUTHOR]

Composite structures and materials are used in aerospace, marine and automotive applications due to their light weight characteristics. By using rice husk ash (RHA) as natural binder to replace epoxy resin, it improves the characteristic of the composite laminated structure. Rice husk has become an important ingredient in silica, silicon carbide, and silicon nitride because of its high a silicon content. This paper evaluates the performance of laminated composite plate in a drop-weight impact testing. Two plates are attached to the test rig in the particular desired impact orientation. The main advantages of this process are the plates provide more realistic drop-weight impact and data. Data from the impact test was collected and analysed to evaluate the material properties of epoxy resin and RHA. Results show RHA's energy absorption is better and it has more deformation to prevent structure failures compared with epoxy resin. This paper aims to evaluate the application of RHA as a geopolymer binder and flax fibre as an alternative material to glass fibre in the composites industry. [ABSTRACT FROM AUTHOR]

• A SCS panel with energy absorption connectors (SCS-EC) was proposed for impact resisting. • Drop-weight impact tests and Finite Element simulations were conducted on the SCS-EC. • Failure modes and impact responses of the SCS-EC were obtained. • The effect of variant parameters on impact response of the SCS-EC was analyzed. This paper developed a new steel-concrete-steel sandwich panel with energy absorption connectors (SCS-EC) for resisting impact load, and the impact responses of the SCS-EC were studied by conducting impact tests and Finite Element (FE) simulations. The failure modes of the SCS-EC under impact loading could be categorized into two types based on the crushing magnitude of the energy absorption connector (EC). The EC was found to effectively dissipate impact energy via the plastic deformation of pleated steel plates and the compression of aluminum foam fillers. The steel-concrete-steel (SCS) panel showed the combination of global and local deformation under impact loading. Moreover, the influences of pleated plate thickness (t p) and angle (θ p), aluminum foam filler and initial momentum on the impact performances of the SCS-EC were studied quantitatively. The results showed that the SCS-EC exhibited enhanced impact resistance via increasing initial momentum of the impactor as well as filling aluminum foam in the EC and assuring the maximum crushing displacement of the EC being equal to its densification displacement. [ABSTRACT FROM AUTHOR]

Implementing measures to enhance collision energy absorption of a racing vehicle is essential to protect the vehicle and its driver and maximize the driving performance. In this study, based on the energy absorption characteristics of composites, the requirements of competition rules, and the overall vehicle arrangement, a preliminary design of an impact attenuator is performed. This paper will design the basic model with rules requirement in second section, and refer existing composite material-corrugated beam energy absolved structure, and write in half-corrugated beam energy absolved structure, so the model structure can be parameterize. Based on commercial nonlinear finite element analysis software LS-DYNA, established the numerical model. Subsequently, the optimization is divided into structural and lay-up optimizations. Using the LS-OPT software, and based on the response surface analysis method, the structure is optimized to obtain a composite impact attenuator model with the highest possible specific energy absorption. The lay-up of the model is optimized to attain a final lay-up with the minimum weight. Quasi-static axial compression and dynamic drop-weight impact tests are conducted to verify the optimization design. Finally, the composite impact attenuator of the racing car with high energy absorption efficiency, high specific energy absorption, and light weight is achieved. [ABSTRACT FROM AUTHOR]

Impact damage resistance of the sandwich composites affects the structure reliability and crucially depends on the core. The weak junction of core unit-cell walls causes a catastrophic failure on sandwich composites under impact load. Stitching is an efficient and easy way to obtain the strengthened core unit-cells. In this study, the impact behavior of glass/epoxy face sandwich composites integrated with a novel 3D multi-layer stitched core were investigated. The peak forces and absorbed energy of sandwich composites were increased as the number of core layer increased. The increase in core layers and core dimensions caused more flexible sandwich composites. The core was more effective in the energy absorption mechanism of the sandwich composites than faces with the increased stitching density and decreased unit-cell size of core. The number of core layers, dimensions of core unit-cells and stitching density were found to be most important parameters for the impact failure of sandwich composites. [ABSTRACT FROM AUTHOR]

The objective of this research is to compare the numerical and experimental results with a closed-form solution for the dynamic responses of composite sandwich panels subjected to a low-velocity impact. An equivalent twodegree-of-freedom system is used to predict the response at different boundary conditions. The experimental results were obtained from drop-weight impact tests. Numerical calculations were performed using the LSDYNA software to verify the analytical results. The numerical simulation showed a good agreement with experimental data. Meanwhile, with increasing impact velocity, the analytical model showed some disagreement with experiment. This can be explained by the static analysis and minimization of the potential energy used in the model. [ABSTRACT FROM AUTHOR]

U-type corrugated sandwich panels exhibit excellent mechanical properties, and their application in the design of ship structures meets the requirements of the future development of ship and ocean engineering structures. In this study, the dynamic response of U-type corrugated sandwich panels under low-velocity impact using a drop-weight apparatus at the impact velocity of 4.43 m/s was measured and compared with finite element predictions. Moreover, the effect of impact velocity and location were evaluated. Both the experimental and simulation results indicated that the deformation modes of the front face were localized indentation, membrane stretching and wrinkle formation around the contact area between the front face and indenter, however the deformation modes of the corrugated cores were indentation and global bending. The dynamic responses of the sandwich panel determined through experiment and numerical simulation were consistent, revealing that the numerical simulation demonstrated reasonable accuracy. When the impact velocity increased from 2.8 to 4.85 m/s, the loading process and deformation modes of the sandwich panel were mainly influenced by the properties of the structure. The transverse impact resistance performance of the U-type corrugated sandwich panel was better than the longitudinal performance, owing to the higher number of core cells involved in deformation and energy absorption. • A low-velocity impact test using a large-scale sample is firstly conducted. • Deformation modes of the front face, core and back face are concluded. • The initial impact energy minimally influences the loading process. • The sandwich panel behaves better impacting in the transverse direction. [ABSTRACT FROM AUTHOR]

[Display omitted] • U-shaped PU-based polymer concrete is developed. • Statistical and computational analysis was performed on impact resistance data. • The effects of PU resin content on the impact resistance was evaluated. • PU-based Polymer concrete revealed high impact times and energy absorbed capacity. • SVM model supported with K -fold cross-validation was used to predict the failure Strength (N 2) blows. The impact resistance of Polyurethane (PU)-based polymer concrete was investigated using U-shaped specimens tested on a newly designed drop-weight impact test device. The PU-based polymer concrete samples was obtained by mixing natural sand and PU matrix using 85:15 and 90:10 ratios, and normal concrete samples were tested for comparison. The results revealed that the PU binder composition greatly enhanced the impact times and energy absorption capacity. The U-shaped specimen was predetermined the position of the crack and reduced the dispersion of results. The coefficient of variation (COV) of 38.07% is the maximum value obtained in this study, lower than the value obtained in ACI 544 2R impact testing procedure. The AI-based model' result indicates that the prediction skills of the support vector machine (SVM-M3) performed very well with R 2 = 0.9575 and 0.9814 in the training and testing stage, respectively. Therefore, the proposed model had high accuracy in predicting the failure strength (blows) of PU-based polymer concrete samples. [ABSTRACT FROM AUTHOR]

The resiliency of advanced laminated nanocomposite materials to mitigate impact load is an essential characteristic for material selection and product design. This paper investigates the effect of nanofillers and its effect on the damage resistance performance of a newly developed woven Kevlar fabric. Three types of nanofillers were investigated: (1) Silicon carbide (SiC), (2) aluminum oxide (Al 2 O 3), and (3) multiwalled carbon nanotube (MWCNT). The nanofillers were dispersed using shear mixing and sonication into the epoxy to reinforce Kevlar fabric. Moreover, the effect of the nanofiller's concentration on the damage resistance performance was analyzed. All specimens had 10 layers of Kevlar fabric (KM2plus) stacked with a 0° angle. To evaluate the damage resistance performance a drop-weight impact test was conducted using a maximum drop height of 100 cm. X-ray diffraction was used to evaluate the level of material damage caused by the impact load. The addition of nanofillers enhanced the flexural properties of the composite and as well as its resiliency towards impact loads. In particular, the 0.5 wt% MWCNT laminated Kevlar/epoxy composite possessed the highest impact damage resistance capacity. Furthermore, the damage evolution was not observed within the impact area and in the surrounding areas for specimens with 0.5 wt% MWCNT. Therefore, the results indicate that the optimal nanofiller content for Kevlar KM2plus/epoxy nanocomposites is 0.5 wt% MWCNTs. • The effect of different nanofiller on the damage resistance of Kevlar KM2plus/epoxy nanocomposite was investigated. • Silicon carbide (SiC), aluminum oxide (Al 2 O 3) and multiwalled carbon nanotube (MWCNT) were used as nanofillers. • Flexural, drop weight, SEM and X-ray tests were performed to evaluate the mechanical integrity of the nanocomposites. • The optimum nanofiller content is 0.5 wt% MWCNTs. [ABSTRACT FROM AUTHOR]

In order to investigate the static and dynamic flexural behavior of ultra-high-performance fiber-reinforced concrete (UHPFRC) beams, twelve half-scale beams (125 × 250 × 2438 mm) were fabricated and tested under quasi-static and drop-weight impact loading conditions. Four different volume fractions (v f) of steel fibers, i.e., 0, 0.5, 1.0, and 1.5%, and shear reinforcements were considered as test variables. Force-displacement relations and energy dissipating capacity were derived to evaluate and compare the impact resistance of the UHPFRC beams. The force-displacement curves, excluding inertial effects, were obtained by a proposed process using D'Alembert's dynamic equilibrium principle, and energy dissipating capacity was calculated by integrating the overlapped force-displacement curves of sequential impact tests. Furthermore, the equivalent blast load was converted from the impact force to extend the utilization of impact test results for substituting difficult blast tests on structural specimens. Lastly, the test results indicate that the addition of steel fibers and stirrups enhanced the static and impact resistances of the UHPFRC beams in terms of higher load carrying capacity, higher energy dissipating capacity, and lower maximum and residual displacements. As for specimens without steel fibers and stirrups, brittle shear failure occurred under static and impact loading conditions. [ABSTRACT FROM AUTHOR]

In this study, the impact resistance of coral concrete with different carbon fiber (CF) dosages subjected to drop-weight impact test was investigated. For this purpose, three concrete strength grades (C20, C30, C40) and six CF dosages (0.0%, 0.3%, 0.6%, 1.0%, 1.5%, and 2.0% by weight of the binder) were considered, and a total of 18 groups of carbon fibers reinforced coral concrete (CFRCC) were cast. For each group, eight specimens were tested following the drop-weight impact test suggested by CECS 13. Then, the two-parameter Weibull distribution theory was adopted to statistically analyze the variations in experimental results. The results indicated that the addition of CFs could transform the failure pattern from obvious brittleness to relatively good ductility and improve the impact resistance of coral concrete. Moreover, the impact resistance of CFRCC increases with the CF dosage increasing. The statistical analysis showed that the probability distribution of the blow numbers at the initial crack and final failure of CFRCC approximately follows the two-parameter Weibull distribution. [ABSTRACT FROM AUTHOR]

Three-point bending tests on notched beams of three types of steel fiber-reinforced self-compacting concrete (SFRSCC) have been performed by using both a servo-hydraulic machine and a drop-weight impact instrument. The lo ading rates had a range of six orders of magnitude from 2.20 × 10 -3 mm/s (quasi-static) to 2.66 × 10³ mm/s. These SFRSCCs had the same matrix, but various types of steel fiber (straight and hooked-end) and contents (volume ratios), 0.51%, 0.77% and 1.23%, respectively. The results demonstrate that the fracture energy and the flexural strength increase as the loading rate increases. Moreover, such tendency is relatively moderate at low rates. However, at high rates it is accentuated. For the 0.51% fiber content, the dynamic increase factors of the flexural strength and the fracture energy are approximately 6 and 3, while for the 1.23% fiber content, they are around 4 and 2, respectively. Thus, the higher the fiber content the less rate sensitivity there is., Competing Interests: The authors declare no conflict of interest.