Low Impact Resistance Research Articles

An experimental study on the low velocity impact resistance of fibre metal laminates under successive impacts with reduced energies

The response of Glare 3 and Glare 5 to repeated impacts and dropped tools was experimentally investigated using drop weight equipment. Two repetition sequences were tested. The first sequence consisted of successive impacts with the same impact energy, but lower than the first impact. In the second sequence the rebound energy of one impact was taken as the impact energy for the subsequent impact. This sequence represents the drop weight impact.The damage was evaluated using visual inspection and ultrasonic C-scan. Three categories of impact damage were observed: visible deformation without internal or external damage, visible internal damage (C-scan) without external damage, and visible internal and external damages.The “threshold energy” defined as the magnitude of maximum impact energy in successive impacts that caused no further damage after the first impact. For the successive impacts with energy between the threshold energy and the first impact, repeated impacts were observed to cause damage propagation. Successive impacts with impact energy less than the threshold did not reveal any effect on the structural integrity.The dropped tool sequence revealed that the rebound energies do not have a considerable effect; the force–time and force–displacement curves for Glare laminates did not change with successive rebound impacts. Therefore, it can be concluded that damage propagation due to rebound energies is negligible.

Design and analysis of low velocity impact on thermoplastic hat section with curvilinear profile

A hat section was designed and developed for maximum impact energy absorption and/ or transmission under low velocity impact. Towards this, different hat sections, having material properties of thermoplastic, were modeled and investigated numerically using finite element analysis (FEA) in the range of 20-50 J impact energy. In the study it was experienced that the design configuration of hat section with curvilinear profile (HSCP) was excellent in energy attenuation capacity and for even distribution of maximum impact force around and along the hat section under low velocity impact loading. To validate the numerical findings, polypropylene copolymer (Co-PP) HSCP and low density polyethylene (LDPE) HSCP were developed and evaluated experimentally in the said impact energy range. A correlation was established between FEA and experimental test results, thereby, validating a numerical model to predict results for other thermoplastic materials under given range of impact energy. The LDPE HSCP exhibited better performance as compared to Co-PP HSCP in the said range of impact energy. The findings of this study will enable the engineers and technologists to design and develop low velocity impact resistance devices for various applications including devices to protect bone joints.

Tensile Properties of Woven Carbon/Kevlar Reinforced Epoxy Hybrid Composite

Carbon fibres and Kevlar fibres are among the commonly used fibres in the composite industry. As carbon fibres usually known for its superior strength, its low impact resistance limited its application in the industry. However, further research found that combining the high strength fibres with more ductile fibres like Kevlar could improve the material’s impact resistance. This hybrid effect was also found to be most effective by using intra-ply woven hybrid fibres in the composite. In this work, hybrid composite material was fabricated by using woven carbon-Kevlar cloths with epoxy matrix and the mechanical properties are determined at 0 ̊, 45 ̊ and 90 ̊. The hybrid composite material was found to have highest tensile strength at 0 ̊ (carbon) direction. As the material’s strength and tensile behaviour are different at every fibre types, the selection of fibre direction of the woven cloth in loading is an important criteria in any applications.

Thermal, mechanical, and physical properties of seaweed/sugar palm fibre reinforced thermoplastic sugar palm Starch/Agar hybrid composites

The aim of this research is to investigate the effect of sugar palm fibre (SPF) on the mechanical, thermal and physical properties of seaweed/thermoplastic sugar palm starch agar (TPSA) composites. Hybridized seaweed/SPF filler at weight ratio of 25:75, 50:50 and 75:25 were prepared using TPSA as a matrix. Mechanical, thermal and physical properties of hybrid composites were carried out. Obtained results indicated that hybrid composites display improved tensile and flexural properties accompanied with lower impact resistance. The highest tensile (17.74MPa) and flexural strength (31.24MPa) was obtained from hybrid composite with 50:50 ratio of seaweed/SPF. Good fibre-matrix bonding was evident in the scanning electron microscopy (SEM) micrograph of the hybrid composites’ tensile fracture. Fourier transform infrared spectroscopy (FT-IR) analysis showed increase in intermolecular hydrogen bonding following the addition of SPF. Thermal stability of hybrid composites was enhanced, indicated by a higher onset degradation temperature (259°C) for 25:75 seaweed/SPF composites than the individual seaweed composites (253°C). Water absorption, thickness swelling, water solubility, and soil burial tests showed higher water and biodegradation resistance of the hybrid composites. Overall, the hybridization of SPF with seaweed/TPSA composites enhances the properties of the biocomposites for short-life application; that is, disposable tray, plate, etc.

Damage tolerance assessment of the interface strength gradation in thermoplastic composites

Abstract The newly developed hybridization approach for thermoplastic composites, based on the gradation of the interlaminar interface strength (IGIS design), was used to prepare polypropylene/glass fibre composites by properly alternating layers of reinforcing fabric with compatibilized and not compatibilized polymeric films. Maleated polypropylene was used to improve the matrix/fibre interface strength. The flexural and low-velocity impact characterizations showed that the use of the coupling agent improved the quasi-static flexural properties through the strengthening of the matrix/fibre interface, but considerably lowered the low velocity impact resistance of the laminate. The use of the IGIS design, which grades the interface strength through the laminate thickness, enabled the fabrication of composites with a favourable combination of flexural properties and impact resistance and proved to be effective in better preserving the integrity of the fibres. The damage after impact has been assessed by means of micro-computed tomography, which elucidated the improving effect of the matrix hybridization on the impact resistance, and acoustic emission analysis, which allowed the identification of the mechanisms responsible for impact energy absorption. The role played by the matrix hybridization sequence was pointed out along with the effective role of IGIS design in the overall mechanical performance of laminates.

Impact behaviour of acrylonitrile-butadiene-styrene after temperature and humidity load

This study deals with acrylonitrile-butadiene-styrene (ABS) which was subjected the drop-weight test before and after temperature and humidity load. ABS is an engineering plastic and also an important engineering terpolymer, which has butadiene part uniformly distributed through the acrylonitrile-styrene matrix and is commonly used in production of automotive interior components. The injection moulded ABS samples were subjected the penetration test at fall height 100 J before and after temperature and humidity load and the results were subsequently evaluated and discussed. It was found out that ABS after temperature and humidity load has lower impact resistance.

小型スピンドル用気体軸受溝のレーザー加工条件の検討

In the data center, which manages a huge amount of information, a hard disk drive which is inexpensive and has a large storage capacity is mainly used. However, since the number of HDD operations increases as information volume increases, it is now required to save HDD power. In response to this problem, development of an air bearing spindle to which an air bearing is applied is being carried out. However, there are no examples that have come into practical use due to low impact resistance and low productivity. In this resear ch, to reduce the dynamic characteristics of the HDD spindle motor, the purpose is to develop a small gas bearing spindle of a new structure. This paper report the processing conditions of bearing grooves by laser processing to obtain the groove processing characteristics required for robust optimum design of bearings.

Impact and post impact behavior of fabric reinforced geopolymer composite

Impact and post impact behavior of fabric reinforced geopolymer composites is investigated in this study. Carbon, E-glass and basalt fabrics are incorporated in the geopolymer matrix. The geopolymer composites are tested for impact resistance to an out-of-plane low velocity impact test, followed by post impact performance testing using residual strength measurement on the sample. Impact properties such as impact energy, energy absorption capacity, and damaged area of the composites were examined for fabric reinforced geopolymer composite samples. The drop weight impact tests were performed on composite samples of 15×15cm. The quality of the samples was examined using C-scan in ultrasonic vibration mode and μCT before and after impact test. The post impact behavior of the composite samples was characterized using four point bending tests. Fiber orientation and alignment was observed using SEM. The results obtained showed that E-glass fabric reinforced composites show slightly better performance than carbon reinforced composites. Especially the damaged area is smaller for E glass composites. Basalt fabric reinforced composites have low bending strength and very low impact resistance. The energy absorption in E-glass is due to post-debond fiber sliding phenomena and in carbon fiber to fiber pull out from the composite. The smaller damaged area is attributed to the higher elastic energy absorption of E-glass fibers. The residual strength of carbon and E-glass composites decreased in relation to the size of the visually damaged area, meaning that no invisible damage took place.

Flexural Performance of Alkali-Activated Slag Cements under Quasi-Static and Impact Loading

AbstractEffects of silicate modulus (Ms) of an activator solution and the matrix components of alkali-activated slag cement (AASC) on the flexural parameters of AASC mortars were investigated under static and low-velocity impact loadings. AASC mixtures in two different Ms (SiO2/Na2O) ratios were prepared by the partial replacement of ground granulated blast-furnace slag (GGBFS) with fly ash (FA), metakaolin (MK), and silica fume (SF). Impact load was generated by a free-fall of a hammer onto the simply supported notched beams from different heights. Test results showed that SF-incorporating AASC had similar impact resistance to the control AASC mixture at all tested velocities while the MK-incorporating AASC had significantly lower impact resistance with an Ms ratio of 0.8. The increase of Ms ratio had a profound effect only in the MK series. The dynamic increase factors (DIF) in AASC mixtures increased with impact velocity. Dynamic increase factors were found to be higher in the AASC mixtures having poro...

Film Performance of Poly(lactic acid) Blends for Packaging Applications

Poly(lactic acid) (PLA), a biodegradable thermoplastic derived from renewable resources, stands out as a substitute to petroleum-based plastics. PLA based films for food packaging has been an area of both commercial and research interest within the context of sustainability. In spite of its high strength, packaging applications have been limited because PLA is more brittle than traditional oil-based plastics. Because of this, films display low tear and impact resistance and produce a loud crackling sound when manipulated. Although many studies address the toughening of PLA in the bulk, little attention has been placed on the film performance. The present study is aimed at providing a survey of binary PLA based blends with other biodegradable and non-biodegradable plastics. Acrylic impact modifier (AIM, 5 wt. %), ethylene vinyl acetate (EVA, 20 wt.%), polyhydroxyalkanoate (PHA, 10 wt.%), polycaprolactone (PCL, 30 wt.%), polybutylene succinate (PBS, 20 wt.%) and polypropylene carbonate (PPC, 30 wt.%) were each blended with PLA through single-screw extrusion and converted into films via the blown-film process. Tear and impact resistance, heat seal strength, and noise level were measured. EVA, PHA, PCL, and PBS improved the tear resistance with EVA having the highest effect (>2x). Similarly AIM, EVA and PPC improved the resistance of the film to impact-puncture penetration. Heat seal strength was significantly improved by the PHA and moderately increased by AIM (2x) and EVA. Additionally, we proposed a method to quantify the annoyance of the noise made by the films upon manipulation. PCL and PBS significantly reduced the annoyance level of the films.

Recent advances in epoxy resin, natural fiber-reinforced epoxy composites and their applications

The versatile characteristic of epoxy and its diversity made it suitable for different industrial applications such as laminated circuit board, electronic component encapsulations, surface coatings, potting, fiber reinforcement, and adhesives. However, the pervasive applications in many high-performance field limited the epoxy use because of their delamination, low impact resistance, inherent brittleness, and fracture toughness behavior. The limitations of epoxy can be overcome by incorporation and modification before their industrial applications. Currently, modified epoxy resins are extensively used in fabrication of natural fiber-reinforced composites and in making its different industrial products because of their superior mechanical, thermal, and electrical properties. Present review article designed to be a comprehensive source of recent literature on epoxy structure, synthesis, modified epoxy, bio-epoxy resin, and its applications. This review article also aims to cover the recent advances in natural fiber-based epoxy composites and nanocomposites research study, including manufacturing techniques and their different industrial applications.

In-process detection of chipping in ceramic cutting tools during turning of difficult-to-cut material using vision-based approach

Ceramic cutting tools are prone to failure by chipping and fracture rather than gradual wear mainly because of their low impact resistance. This results in poor surface finish and low dimensional accuracy of the machined parts. In this work, a vision-based approach has been developed to detect the onset of chipping in aluminum oxide ceramic cutting tools during the dry turning of AISI 01 oil-hardening tool steel. The profile of the workpiece surface opposite the cutting tool was captured during the turning using 18-megapixel DSLR camera at a shutter speed of 0.25 ms. The surface profile of the workpiece was extracted to sub-pixel accuracy using the invariant moment method. The effect of chipping in the ceramic cutting tools on the surface profile signature of the machined workpiece was investigated using autocorrelation analysis. Chipping in the ceramic tool was found to (i) cause the peaks of autocorrelation function of the workpiece profile to decrease rapidly as the lag distance increased and (ii) cause the envelope of the peaks of the autocorrelation function to deviate significantly from one another at different workpiece rotation angles. The sum of squared deviation (SSD) of the envelope of the peak of autocorrelation function was also found to increase sharply right after tool chipping. Significant variations in the SSD at different workpiece rotation angles were observed beyond the cutting time of 11.1 s because of the continuous chipping of the ceramic insert during turning.

Effect of impactor shapes on the low velocity impact damage of sandwich composite plate: Experimental study and modelling

An experimental and numerical analysis of the influence of impactor shapes on the low velocity impact performance of aluminium sandwich composite plates has been carried out. The aluminium composite panels were manufactured by using two aluminium sheets and a low density polyethylene core under heat and pressure, which shows the outstanding properties of low weight, good rigidity and impact resistance. Experimental tests were performed using drop weight test machine, samples were impacted using steel conical, ogival, hemispherical and flat impactors, all 12 mm in diameter, for different initial impact energies of 29.43 J and 44.15 J and specimen thickness of 4 mm containing three different parts (0.5 + 3.0 + 0.5). A three dimensional non-linear finite element model is developed for simulating the impact behaviour of sandwich composite plate and the ABAQUS/Explicit commercial program was used. The face sheet material aluminium alloy 3003-O of the plate was modelled as isotropic with elastic–plastic characteristics. The description of the material characteristic of the attenuator was made by means of the Johnson–Cook elastic–plastic law. The material constitutive law of the Al 3003 plates has been implemented in a user-defined subroutine UMAT. The foam core was modelled as a crushable foam material. The finite element results showed a good correlation to the experimental data in terms of contact-force histories, energy histories, absorbed energy, and failure of the sandwich composite was observed between the experimental data.

Effect of temperature and hybridisation on the low velocity impact behavior of hemp-basalt/epoxy composites

This work focuses on the experimental investigation of the residual flexural strength of hemp/epoxy, basalt/epoxy and hybrid (hemp-basalt)/epoxy composite laminates subjected to low velocity impact damage at different temperatures. These specimens were subjected to a low velocity impact of 1.5 m/s with an incident impact energy of 2.17 J using an instrumented drop weight impact tester at three different temperatures of 30 °C, 50 °C and 65 °C. The residual flexural strength of the post impacted specimens were measured by the conduction of three point bending test in a 100 kN universal testing machine with acoustic emission monitoring. The effects of temperature and basalt fiber hybridisation on the damage initiation, propagation and onset of failure were investigated using the magnitude of AE cumulative counts at different stages of loading. The results show a reduction in impact strength and residual flexural strength after impact at elevated temperatures. Lower impact resistance shown in the impact test results for all three types of composites at elevated temperatures indicate the effect of temperature which leads to inferior impact properties. It was evidenced from the impact and dynamic mechanical analysis (DMA) carried out on the composites that hybrid composites have better residual flexural strength and impact properties compared to non-hybrid composites.

Water absorption and mechanical property of an epoxy composite coating containing unoxidized aluminum particles

Abstract In this work, an unoxidized aluminum particle/epoxy composite coating was prepared onto the surface of the pure epoxy resin to reduce its water absorption and improve its mechanical property and low energy surface impact resistance. Unoxidized aluminum particles were prepared using arc spraying under the protection of nitrogen. The diffusion coefficient of sample began to decrease and then increased with increasing the content of aluminum particles in the composite coating. The minimum value was 2.7 × 10 −8 m 2 /s at a critical concentration of 6% of aluminum particles, 38% lower than that of pure epoxy resin. The sample with 6% aluminum particles had the maximum tensile and bending strengths of 38.9 MPa and 94.6 MPa, respectively. Aluminum particles could effectively reduce the impact of the epoxy resin suffered. The direction of the impact was changed, and avoids the micro-crack to extend unidirectionally.

Effect of Fiber Length on Direct Tensile and Impact Strength of Cmentitious Materials Containing Silica Fume

This study is aimed to evaluate the tensile strength and impact resistance of cementitious materials which comprise steel fibers and silica fume in the mixes. Material variables include water-binder ratio, dosage of silica fume, steel fiber length and dosage. A designed tensile strength was used to perform the direct tensile in this study. Test results indicate that the compressive strength, splitting tensile strength and direct tensile strength of specimens for fiber length of 60 mm are higher than that of 35 mm. The inclusion of fibers in specimens containing silica fume has higher compressive and tensile strength; and lower impact resistance than the specimens made with silica fume. Incorporation of steel fiber and silica fume in composites achieves significantly higher increase in compressive strength, splitting tensile strength, and direct tensile strength than only individual use of steel fiber or silica fume and decrease in impact resistance than only individual use of steel fiber. Finally, the proposed direct tensile testing method is suitable for determining the tensile strength of fiber reinforce cementitious materials and generating the tensile stress-strain curves easily.

스티렌/부틸아크릴레이트/메틸메타아크릴레이트 삼원 공중합체의 투명성 및 기계적 물성

대표적인 범용 플라스틱인 폴리스티렌의 장점인 투명성을 유지하면서 단점인 낮은 내충격성을 보완하고자 투명한 아크릴레이트계 고분자의 단량체인 butyl acrylate(BA)와 methyl methacrylate(MMA)를 styrene(SM) 단량체와 현탁중합으로 중합하여 3원 공중합체를 제조하였다. SM/BA 2원 공중합체와 SM/BA/MMA 3원 공중합체를 제조하여 각각의 물성을 비교하였다. 또한 가장 충격강도가 좋은 3원 공중합체에 가교제인 dicumyl peroxide(DCP)의 함량을 변화시키면서 가교반응시켰다. 단량체의 중합조성비 및 가교제의 함량이 공중합체의 열적, 기계적 물성과 광학적 특성에 미치는 영향에 대해 확인하였다. 결론적으로 butyl acrylate의 함량이 증가할수록 충격강도는 높아지지만 SM/BA 2원 공중합체는 특정 조성에서 불투명하게 된다. 하지만, SM/BA/MMA 3원 공중합체는 모든 조성에서 투명하면서 비교적 높은 기계적 물성을 나타내었다. 또한 DCP의 함량이 증가할수록 기계적 물성을 높일 수 있었으나 투명성은 점차 낮아졌다. In order to improve the low impact resistance of polystyrene without harming its transparency the styrene monomer was copolymerized with transparent butyl acrylate (BA), and methylmethacrylate (MMA) to obtained a poly(styrene-co-butylacrylate) P(SM-co-BA) and a terpolymer copolymer P(SM-co-BA-co-MMA). The polymers were then cross-linked with the aid of a cross-linking agent dicumylperoxide (DCP), and their mechanical and optical properties were tested. It was found that the contents of monomers and DCP affect the mechanical, thermal, and optical properties of the polymers. An increase in BA contents in P(SM-co-BA) and P(SM-BA-MMA) improved the mechanical strength, but the optical properties remained the same with some exception for P(SM-co-BA). An increase in the DCP contents improved the mechanical but found losses in the optical properties.

Mechanical performance optimization through interface strength gradation in PP/glass fibre reinforced composites

A new design for thermoplastic composites based on the gradation of the interlaminar interface strength (IGIS) has been developed with the aim of coupling high impact resistance with high static properties. IGIS laminates have been prepared by properly alternating layers of woven fabric with layers of compatibilized or not compatibilized polymeric films. To prove the new concept, polypropylene (PP) and glass fibres woven fabrics have been used to prepare composites by using the film stacking technique. Maleated PP, able to compatibilize polypropylene with glass fibres, has been used to manage the interface strength layer by layer.The flexural and low-velocity impact characterizations have shown that the presence of the coupling agent in conventional composite structures (prepared with fully compatibilized polymeric layers) improves the static flexural properties through the strengthening of the matrix/fibre interface but considerably lowers the low velocity impact resistance of the composite, in terms of maximum load before fibre breakage and recovered energy after impact. The use of the IGIS design, that grade the interface strength through the laminate thickness, allows to prepare composites with both high flexural properties and high impact resistance, without affecting the balance and type of the reinforcement configuration.

Fabrication and characterization of three dimensional woven carbon fiber/silica ceramic matrix composites

Carbon fiber reinforced fused silica composites exhibit the advantages of excellent mechanical properties, high heat resistance, low thermal expansion and low density, but low impact resistance or toughness. A novel modified slurry impregnation and hot pressing (SIHP) method was adopted to fabricate a new type of three dimensional orthogonal woven structure carbon fiber reinforced silica ceramic matrix composites (3D Cf/SiO2 CMCs) with higher density and lower porosity. Physical characterization, flexural behavior, impact performance and toughening mechanism of the composites were investigated by three-point bending tests, impact tests, and scanning electron microscopy analysis. The 3D Cf/SiO2 CMC showed a higher flexural strength in both warp (201.6%) and weft (263.6%) directions than those of pure SiO2 and failed at a non-brittle mode due to the fiber debonding and pullout, and a delaminated failure of the 3D preform. The maximum impact energy absorption of the 3D Cf/SiO2 CMC was 96.9 kJ/m2, almost 4 times as much as those for typical other carbon fiber reinforced CMCs.

Behaviour of Ferrocement SlabsContaining SBR Under Impact Loads

The main aim of this work is to investigate the behavior of Ferrocement slabs under impact loading. A total of 48 Ferrocement slabs were constructed and tested, 36 slabs tested under low velocity impact and 12 slabs tested under high velocity impact, in addition,the main parameter considered in the present investigation was number of wire mesh layers, content of (SBR) polymer andheight of falling mass (falling velocity). For low velocity impact,This test was performed in terms of the number of blows required to cause first crack and ultimate failure. The test was applied on square slabs of dimensions (500 × 500 × 50 mm) subjected to repeated impact blows by falling mass (1300 gm) dropped from three heights (2.4 m) , (1.2 m) and (0.83 m) at 56 day age. The number of required blows for the first crack and final failure was recorded. The mode of failure and the crack pattern were also observed. For high velocity impact test, a (500×500×50 mm) slabs were tested by 7.62 mm bullets fired from a distance of (15m) with a striking velocity of (720m/sec.). The spalling, scabbing and perforation were observed and discussed. The results exhibited that the number of blows which were required to make the first crack and failure, increased with increase of polymer content and number of wire mesh layers. Also for high velocity impact test, it can be noted that the area of scabbing and area of spalling decreased with the increase of polymer content and number of wire mesh layers compared with reference mixes. The compressive strength, splitting tensile strength and flexural strength increased with increase the polymer content. Based on extensive works , found that low velocity impact resistance of polymer modified Ferrocement slabs was greater than the reference mix slabs, it was found that the number of blows that needed to produce the first crack and ultimate failure increased with increase the polymer ratio of 3% to 5% and to 10%, and with increased the number of layers of reinforcing with wire mesh when comparing these results reference mix.