Quasi-static Penetration Tests Research Articles

Experimental analysis of the quasi-static penetration test on fiber metal laminated plate reinforced by nano-silica

FMLs are lightweight hybrid materials that possess specific static properties, impact resistance, fracture resistance, and fatigue resistance. These characteristics make FMLs highly desirable for various applications in the transportation industry (Hu et al., 2015 Dec 1) [2].The present study aims to scrutinize the energy absorption and strength characteristics of a kind of Fiber Metal Laminate (FML) reinforced with Nano silica (0, 0.3, 0.6, and 0.9 wt %) that is fabricated from braided fiberglass and carbon fiber sleeve and aluminum 2024-T3. Sleeve-type braided fiberglass, carbon fiber and highly adhesive resin were introduced as interlayers. The arrangement of FMLs layers was in 2 types, first AL/Glass/Glass/Glass/Glass/AL and second AL/Glass/Carbon/Carbon/Glass/AL. The produced FMLs were tested to evaluate the behavior and strength characteristics under quasi-static indention. Quasi-static indentation test performed with spherical head penetrators at a 5 mm/min rate. The experiment continued until the indenter fully penetrated the specimen. These FMLs crushed progressively and are unlikely to fail under catastrophic failure, although specimens with 0.6% Nano silica in glass fiber and specimens with 0.3% in the glass and carbon fiber have better performance. A comparison of the results of glass FMLs with hybrid FMLs shows that Nano silica-reinforced glass fibers have achieved better results than hybrid fiber. To study the structure of amplified FMLs, electron microscopy (SEM) imaging was used which showed that in FMLs with better results, Nano silica was evenly distributed on the layer of epoxy resin. The results also indicate that the mechanical performance of a new FML has a good potential to be applied as a new and efficient energy absorber.

Investigation of penetration behavior of combined geometry shells at quasi-static and intermediate strain rates: An experimental and numerical study

In this study, the penetration/perforation behavior of a core material with previously determined static and dynamic crushing characteristics was investigated both experimentally and numerically. Penetration/perforation problems occur due to shrapnel effect when sandwich structures containing energy-absorbing core materials by crushing are exposed to blast loads. The penetration behavior of combined geometry shells consisting of a hemispherical cap and a cylindrical segment was investigated experimentally using blunt, conical and hemispherical penetrator tips. The quasi-static penetration tests were performed in a universal test machine, and the intermediate strain rate penetration tests were performed in a drop weight test device. The numerical models of penetration tests were implemented in LS-DYNA at the test strain rates as well as at the higher strain rates. Results showed that different penetrator geometries induced damage forms of symmetrical tearing, petaling, plugging and inversely formed hemispherical domed cone. The increase in the thickness of core geometry resulted in a decent increase in force–displacement curves, as average of force levels increased around 140%, 200% and 220% for blunt, conical and hemispherical tip penetrators, respectively. Numerical results indicated very good correlation with experimental work and enabled to investigate effect of strain rate and micro-inertia over numerical models at elevated penetrator velocities. Penetration behavior was found to be affected from micro-inertia effects up to a threshold displacement of 4 mm for thicker and 5 mm for thinner core units and strain rate effects were found to be dominant beyond that point.

Quasi-static penetration property of 3D printed woven-like ramie fiber reinforced biocomposites

The present work aimed to study the penetration behaviors of 3D printed continuous ramie yarn reinforced polylactic acid (PLA) based woven-like and non-woven-like biocomposites. The architectures were produced by in-situ impregnated 3D printing process according to a novel interweaved and a conventional printing path (unidirectional and orthogonal). The quasi-static penetration test (QSPT) was conducted to evaluate the effect of 3D printed architecture, support span to indenter diameter ratios (SIRs) and fiber reinforcement on the penetration property of biocomposites. The backlight method was adopted to real-time capture the damage process of the biocomposites under QSPT. The results showed that the penetration property and energy absorption capability of the 3D printed samples increased with decreasing SIR and with the addition of continuous ramie yarn. The energy absorption and maximum penetration force of the 3D printed biocomposites with woven-like architecture increased by 31.2 %, and 18.0 % compared with non-woven-like architecture (unidirectional) at SIR = 5. The structure-penetration property relationship of 3D printed woven-like architectured biocomposite was revealed through the analysis of multiscale failure features and penetration damage mechanisms.

The effect of capsulated nanosilica-epoxy healing agents on the self-healing ability of glass fibers-epoxy composites under mechanical loading

In this study, the effect of using an epoxy healing agent containing silica nanoparticles instead of the neat epoxy healing agent on the self-healing ability of glass fibers/epoxy composites under the flexural, tensile and shear loadings was assessed. For doing this, in the first step, the silica nanoparticles (0, 1, 2 and, 3 wt.%) were dispersed into the ethyl acetate/epoxy healing agent. Then, these mixtures were encapsulated with the urea-formaldehyde polymer by an in-situ polymerization method. Finally, the glass fibers/epoxy composite containing 14 wt.% microcapsules along with 2 wt.% NiCl2(imidazole)4 catalyst were fabricated. To understand how the mechanical-healing behaviors of these composites under the various mechanical loads, these composites were destructed with a quasi-static penetration test for the creation of delamination damage. The healing process was done by the thermal activation method. The obtained results showed that the highest healing efficiency under the flexural, tensile and shear loads belonged to the composite containing 1 wt.% nanosilica into the healing agent, which were 89.8, 87.8, and 156.8%, respectively. The hackles of microcapsules, reduction in the thickness of microcapsules, formation of nanocomposite healing shell and the agglomeration of silica nanoparticles on the healed area were the influence factors on the healing ability of these composites. This work can give a view for healing the microcracks into composite structures by nanocomposite healing agents, which have the higher healing ability and better performance under mechanical loads than conventional healing agents.

Effects of Bio-Particles on Mechanical and Quasi-Static Punch Shear Behaviors of Glass/Epoxy Composites

In this study, the effect of acorn powder reinforcement at different percentages on the mechanical and quasi-static penetration behavior of glass fiber reinforced composites was investigated. Reinforcement materials used are woven E-glass fiber and cleaned acorn micro powders. Powders were cleansed from impurities with a sodium hydroxide solution. Cleaned powders were mixed with resin by using a mechanical mixing method. Thereafter, resin mixture was applied to glass fibers with hand lay-up method and composite plate was produced by vacuum bag method. Quasi-static penetration tests were performed at room temperature as well as mechanical tests. While 1, 10 and 20 mm/min were selected as quasi-static penetration test speed, tension, compression and three point bending tests were selected as mechanical tests. Force and energy test results of quasi-static penetration tests of composites were compared with each other. Additionally, tensile, compressive and flexural strengths of the composites were investigated.

A natural composite and nanocomposite of luffa fibers and chitosan resin under mechanical tests

This article introduces natural composite and nanocomposite panels of Luffa fibers–chitosan resin; and they are subjected to quasi-static penetration tests and compression experiments to discuss their penetration resistance and compression strength. Natural fibers of Luffa cylindrical sponge were used as the reinforcement and natural chitosan resin was produced from shrimp shells. Specimens with various characteristics were produced through hand layup method and they were subjected to penetration test of a blunt-nose punch. Results demonstrated that there is an optimum mass fraction for chitosan and magnetite nanoparticles to achieve the highest penetration strength; and the best layer configuration is as 0 and 90°, alternately. Furthermore, some glass-chitosan composite panels were produced and comparison of their penetration tests and the corresponding Luffa-chitosan composite experiments demonstrated that in a certain condition, the maximum loads of penetrating the punch into the both composite panels are the same. In second type experiments, quasi–static compression tests were performed on some cubic Luffa–chitosan specimens and results showed that the natural composite cube has significant specific absorbed energy; and by selecting its suitable dimensions, a natural energy absorber can be achieved. Development of the natural Luffa–chitosan composite is suggested, based on sustainability considerations; and using it in the bulletproof vests and armors is presented as a creative idea; due to its natural structure, compatibility with human skin, acceptable resistance against the penetration, its biodegradable ability and simple and low cost production process.

Experimental investigation on the energy absorption characteristics of sandwich panels with layering of foam core under quasi-static punch loading

Quasi-static full penetration tests were investigated on sandwich panels with graded polyurethane foam core and aluminum face-sheets. Results showed that the panels with decreasing foam core density (HL) create more contact force and its amount is 1.5 times the force required to penetrate into panels with increasing foam core density (LH). Also, the indenter needs the highest energy to penetrate into sandwich panel with decreasing foam core density (HL), and its value is 1.32 times the energy required to penetrate into panel with increasing foam core density (LH).

Investigation of the Quasi-Static Penetration Resistance Behaviour of Carbon/Aramid Fibre-Reinforced PP Laminate.

This work presents the experimental results of a quasi-static attempt at the penetration of hybrid and non-hybrid laminates reinforced with aramid and carbon fibres on a thermoplastic polypropylene matrix. The hybrid laminates were prepared in two fibre combinations: carbon–aramid–carbon (CAC), in which the carbon fibres comprised the outer (lining) layers, and aramid–carbon–aramid (ACA) with carbon fibres in their intermediate layers. A quasistatic penetration attempt was performed for two coefficients: SPR—support span to punch diameter ratio, (SPR = 2 and 5). The SPR = Ds/Dp was calculated as the ratio of the support (Ds) to the punch diameter (Dp). A punch with a rounded 9-mm diameter tip was used to penetrate the material. Percentage changes of penetration energy (%E) and of maximum load (%P) compared to a non-hybrid laminate with carbon fibres were calculated in order to estimate the impact of hybridisation on the properties of laminates. The maximum load recorded during a quasi-static penetration test was used to calculate the PSS (punch shear strength) of the laminates. The damage was observed after the penetration test. It was observed that both the order of layers of laminate reinforcement as well as the SPR coefficient used in the test influenced the obtained results and the laminate damage mechanism.

Effects of cryogenic and warm temperatures on quasi-static penetration resistance of carbon-aramid hybrid nanocomposites reinforced using halloysite nanotubes

The quasi-static penetration test of a composite structure aims to measure impact behavior under the out-of-plane loadings without dynamic and rate effects. In this study, carbon-aramid reinforced nanocomposites were manufactured by vacuum-assisted resin transfer molding and hand lay-up techniques and characterized by quasi-static penetration tests. Halloysite nanotubes (HNTs) were added to epoxy resin as nanofillers. Quasi-static punch shear test (QS-PST) was performed using a 12.7-mm cylindrical punch with a 50.8-mm support span. QS-PSTs tests were carried out at −50 °C, −25 °C, 0 °C, 25 °C, and 50 °C to determine the effect of temperature on quasi-static penetration behavior of neat and HNT-reinforced carbon-aramid nanocomposites. Absorbed energy values and penetration force–displacement curves were acquired from QS-PSTs for each sample. Photographs of the front and rear sides of the samples were taken and analyzed. Moreover, the samples were cut from the middle, and the damage throughout the thickness of the composite samples were examined. It was observed that for all test samples, damages increased when the temperatures decreased. For the same temperature, nanoparticle addition to the samples resulted in higher penetration force and less damage. We confirmed the possibility of increasing penetration resistance and energy absorption capacity by adding HNT to carbon-aramid fibers at cryogenic and warm temperatures.

Penetration behaviour of TBM disc cutter assisted by vertical precutting free surfaces at various depths and confining pressures

The ability to improve rock-breaking efficiency of tunnel boring machines in hard rock stratum is significant to improve driving speed and reduce construction cost and time. The undercutting method has been used to improve the rock-breaking efficiency of disc cutters, including the design of curved and multistage cutterheads. The limited radian of curved cutterheads and the number of multistage cutterheads, however, are restricted by the current manufacturing level. We explored mechanical response and rock-breaking efficiency assisted by water jet kerfs as the vertical free surface. We conducted a quasi-static penetration test of the disc cutter considering four kerf depths and three groups of confining pressures. We analysed the surface crack propagation and fractures inside the sample using acoustic emission and computed tomography scanning. We studied the influence of confining pressure and cutting depth of the water jet on penetration force, rock chips, and specific energy. We analysed the failure evolution and stress field of kerf specimens using numerical simulation. The results showed that increasing cutting depth relieved restraint stress and the resulting influence of the confining pressure on removed rock volumes and specific energy was not remarkable. We recommended a kerf depth of greater than 18 mm to reduce penetration force and significantly improve rock-breaking efficiency.

The Effects of Hybridisation of Composites Consisting of Aramid, Carbon, and Hemp Fibres in a Quasi-Static Penetration Test.

The quasi-static penetration properties of hybrid laminates were experimentally investigated. Aramid fabrics, carbon fabrics, and short hemp fibres were applied as the reinforcements of hybrid and non-hybrid composite laminates with polyurethane–polyurea (PUR/PUA) matrix. The laminates were made by hand, in a mould. They were cured at room temperature for 24 h. Hybrid laminates consisted of aramid and carbon layers in two different configurations, i.e., aramid at the innermost layers and outermost layers. Aramid/PUR/PUA and carbon/PUR/PUA composites were fabricated for comparison purposes. Laminates were also prepared via an analogue sequence of laying the reinforcement layers with the addition of 5% by weight of hemp fibres in the PUR/PUA matrix. Quasi-static penetration tests (QSPT) were conducted using a tensile testing machine with a surface-hardened, hemispherical, steel punch (9 mm diameter tip), reflecting the geometry of the Parabellum projectile. A quasi-static puncture test was carried out until the laminate was perforated. The ratio between the support span (Ds) and the punch diameter (Dp) was SPR = Ds/Dp = 5.0. The results showed the influences of laminate hybridisation on the values of absorbed energy, punch shear strength, and damage mechanism in the QSPT test. The addition of hemp fibres to aramid laminates resulted in a positive hybridisation effect. The order of layers of aramid and carbon fabrics in hybrid laminates influenced the results obtained in the QSPT test.

Breakage mechanism of hard-rock penetration by TBM disc cutter after high pressure water jet precutting

To achieve greater efficiency of TBM driving and lower cutter maintenance costs in hard rock formations, the TBM integrated high pressure water jet system was developed. By examining the working modes of water jets and disc cutters, this paper investigates the mechanical response and failure mechanisms for the simple case in which a water jet is first used to cut, followed by disc cutter rock breaking. As disc cutters use penetration-type rock breaking, laboratory quasi-static penetration tests and numerical simulations were carried out for kerf specimen precutting with a high pressure water jet. The influence of kerf parameters on the mechanical behavior of rock breaking was studied, and the mechanisms of surface and internal cracks and fractures were revealed and discussed. The results show that peak penetration force decreases with the increase of kerf depth, and slightly increases with the increase of kerf spacing. The specific energy decreases significantly with the increase of kerf depth and gradually becomes stable once the kerf depth becomes greater than 18.14 mm. The internal cracks formed in shallower kerf specimens mainly include shallow tensile cracks and deep vertical split cracks. However, the internal cracks of deeper kerf specimens incline and bend, extending towards the bottom of the kerf. The theoretically obtained minimum shear load, optimal failure depth, and fragment area all increase with kerf spacing, but the angle of the shear plane remains approximately 45°. These findings may provide some reference for the design and construction of TBMs integrated with high-pressure water jets.

Experimental testing and Numerical modelling of a Kevlar woven – epoxy matrix composite subjected to a punch test

The paper investigates the penetration mechanics of thick-section composites. For this purpose, a series of quasi-static penetration tests on Kevlar 29 (plane wave) /epoxy panels with a nominal thickness of 6.5 mm (14 layers) were designed and conducted. The experiments were performed at different support spans using a blunt geometry for the punch. During the tests, the punch displacements and the applied force on the punch were measured.Finite element (FE) models were created to replicate the quasi - static punch test using the LS-DYNA solver and exploiting a material damage model that allows the reproduction of all the different types of failure occurring during the tests (fibre failure, matrix failure, delamination). The focus is placed on the capability of the model to mimic the experimental damage in order to have a reliable virtual tool able to provide, with high accuracy, the penetration mechanisms and the trend of the absorbed energy during the different phases of penetration. The comparison between experimental data and numerical results is discussed.

Experimental investigation of quasistatic penetration tests on honeycomb sandwich panels filled with polymer foam

In this article, the quasistatic penetration tests were investigated on unfilled and polyurethane foam filled honeycomb sandwich panels. Failure mechanisms, specific energy absorption, interaction mechanisms, and some structural responses were studied. Comparing the three types of the foam filled sandwich panels with unfilled type, indicates that the absorbed energy of the first, second, and third type of the panels are 23%, 33%, and 58% more than unfilled ones, respectively. In addition, the results showed the enhancement in the dynamic strength and remarkably decrease in the damage area of the sandwich structure when its honeycomb core was filled with polymer foam.

Preparation, characterization and properties of shear thickening fluid impregnated fabric composites

Shear thickening is a non-Newtonian flow behavior characterized by the increase of viscosity with the increase in applied shear rate. Due to this remarkable property of shear thickening fluid (STF), it has received extensively attention in armor protection fields. Through a process of impregnation, the STF in body armor has allowed further enhancement without hindering the flexibility of fabrics, which has led to the development of the concept of liquid body armor. In this paper, the STFs were prepared by mechanical stirring of silica nanoparticles dispersed in liquid polyethylene glycol. The rheological properties of as-prepared STFs were tested. Aramid and ultra-high molecular weight polyethylene fabrics were soaked in STF/ethanol solution to make STF/fabric composites. Knife quasi-static penetration tests were performed on the neat fabrics and STF/fabric composite targets for engineered knife on areal density basis. The results showed that compared with the neat fabrics, the STF impregnated fabrics exhibited better penetration resistance without affecting the fabric flexibility.

Laboratory Investigation on Quasi-Static Penetration Testing Using SPT Sampler in Soft Clay Bed

Abstract The standard penetration test (SPT) is one of the most widely used in-situ penetration tests for subsurface exploration. Its suitability for assessing and predicting the design parameters of granular materials has been well appreciated by the geotechnical engineering community over several decades. However, in the case of soft to very soft clays, the correlation between the standard penetration number (N) and the undrained shear strength is poor. In the recent past, tests conducted at a constant rate of penetration, such as the cone penetration test (CPT), ball penetration test, and T-bar penetration test, have become popular in soft clay regions. These tests also have a distinct advantage over SPT in terms of test setup because, in the case of SPT, the entire weight of the sampler and the rod assembly is directly applied on the subsoil, whereas in the case of CPT, the weight of the assembly is supported externally prior to the penetration. This can cause significant operational advantage in case of soft clay deposits. Despite the shortcomings, SPT is still one of the most widely available site investigation tools in the field, as samples are available for inspection and index tests. The operational disadvantages in the case of soft clay deposits can be overcome by altering the penetration process of SPT. A quasi-static penetration at a constant rate rather than a dynamic penetration will help establish a relationship between the penetration resistance and the strength parameters of soft soils. In this article, a quasi-static penetration test using the standard SPT sampler is conducted on reconstituted clay samples in order to develop an empirical correlation with the laboratory vane shear strength. The particle image velocimetry technique is used for detecting the influence zone and plugging during penetration.

Modification of the contact surfaces for improving the puncture resistance of laminar structures

Uncovering energy absorption and surface effects of various penetrating velocities on laminar structures is essential for designing protective structures. In this study, both quasi-static and dynamic penetration tests were systematical conducted on the front surfaces of metal sheets coated with a graphene oxide (GO) solution and other media. The addition of a GO fluid film to the front impact surface aided in increasing the penetration strength, improving the failure extension and dissipating additional energy under a wide-range of indentation velocity, from 3.33 × 10−5 m/s to 4.42 m/s. The coated -surfaces improved the specific energy dissipation by approximately 15~40% relative to the dry-contact configuration for both single-layer and double-layer configurations, and specific energy dissipations of double-layer configurations were 20~30% higher than those of the single-layer configurations. This treatment provides a facile strategy in changing the contact state for improving the failure load and dissipate additional energy.

EFFECTS OF CEMENTATION ON HYDRAULIC CONDUCTIVITY AND ON MECHANICAL STRENGTH OF BINARY PACKING SYSTEMS

ABSTRACT This paper addresses the topic soil stabilization for forest roads applications and analyzes the influence of the hydrated lime in structuring the sand fraction of an artificial soil composed of the sand fractions of two natural soils, simulating natural process of cementation of sands and using binary packing systems. The study included the following topics: (i) characterization of the mechanical strength and hydraulic conductivity of binary systems of the artificial soil; and (ii) effect of hydrated lime in structuring binary packing systems of the artificial soil. Soil samples were submitted to chemical pre-treatment, to obtain clean sand fractions from the two sandy soils with particle diameters ranging from 0.053 to 2 mm, following sieving and separation of them in twenty-two classes with maximum (D)/minimum (d) ratios varying from 5.7 to 13.4. Sequentially, binary packing specimens of the artificial soil were prepared and then stabilized with 2% of a commercial hydrated lime. Next, the specimens were submitted to permeability and quasi-static cone penetration tests, in order to determine their hydraulic conductivity and cone tip resistance. Based on the obtained results, it was concluded that: (i) in the artificial soil, an increase of D/d ratio led to an increase of cone tip resistance and decrease of hydraulic conductivity; and (ii) cementation with hydrated lime reduced the hydraulic conductivity and increased the cone tip resistance.

Quasi-static penetration behavior of plain woven kenaf/aramid reinforced polyvinyl butyral hybrid laminates

Owing to the high cost of synthetic aramid fibers and the necessity for environmentally friendly alternatives, a portion of aramid was replaced by plain woven kenaf fiber, with different lay arrangements and thicknesses. The obtained hybrid composites with aramid and kenaf fibers were used to produce prototypes of army helmet shells. A hybrid composite material was produced using a hot press technique and comprises 19 layers of plain woven kenaf and aramid of various configurations and alternation. The behavior of this composite material on a quasi-static penetration test was studied and was found positive in terms of maximum load carried, energy absorbed in impact, and damage mechanisms. Consequently, a helmet armour was developed that was less costly and more readily available and that which could also be produced by reducing the potential harmful effects of petroleum products, without compromising the ballistic-resistant capability of the material.

Experimental investigation on the quasi-static penetration behavior of curved multi-axial warp-knitted composites

The quasi-static penetration tests of the curved glass/phenolic multi-axial warp-knitted (MWK) composites with two types of preform structures and in three different curvatures were implemented. Three phases — elastic deformation phase, progressive damage phase and tension-shear phase were identified to present the different damage behavior stages of curved glass/phenolic MWK composites under quasi-static penetration. Several types of damage modes including matrix cracking, tension-shear of the materials, fiber fracture and interlayer delamination were revealed based on the load-displacement curves and morphology analyses. The results showed that the reinforcement structure and the curvature of the specimens did provide obvious influence onto the quasi-static penetration behaviors of curved glass/phenolic MWK composites and they could be utilized in pointed purposes according to the different mechanical features.