Effect Of Low Velocity Impact Research Articles

Effect of low velocity impact at different temperatures on hybrid adhesives in aluminium-composite single lap joints

This study aims to investigate the effect of a small stone impact on aluminum composite adhesive joints used in aircraft after exposure to various temperature conditions. In this context, single lap adhesive joints were prepared using 2024-T3 aluminium alloy sheets and 8-layer carbon fiber-reinforced epoxy hybrid composite sheets, with epoxy adhesive applied to the bonding surfaces. In addition, different types of hybrid adhesives were developed by reinforcing pure epoxy adhesive with various ratios (1%, 3% and 5% by weight) of graphene doped and undoped Nylon 6.6 (N6.6) nanofibers produced by electrospinning method to reduce brittleness. Low-velocity impact tests of 1.04 m/s under five different temperatures (−50, −20, 0, 23 and 50°C) were applied to all single lap adhesion joints produced and tensile tests were applied to the non-failed specimens to examine the loading conditions after low-speed impact. It was determined that approximately 1.5 J of the 3 J energy given by the low- velocity impact was absorbed in common in all samples, while the remaining part was returned and some separation occurred within the adhesion area due to the effect of this impact. While the low- velocity post-impact tensile strength of pure epoxy resin was measured as 2230.3 N at 23°C and 585.15 N at −50°C, the highest values were obtained in N6.6 reinforced epoxy adhesive with 1%GNP additive, which was measured as 3206.39 N at 23°C and 641.82 N at −50°C, and increased by 43.7% and 9.6% for 23°C and −50°C, respectively. In addition, the rupture surfaces of the specimens destroyed by the tensile test were examined by scanning electron microscopy (SEM) for damage analysis.

Tensile behavior of the bolt‐jointed GFRP after low‐velocity impact

AbstractBolt joint is one of the most commonly used methods for fiber‐reinforced polymers (FRP) structures whose mechanical properties are quite sensitive to both the stacking sequence and the low‐velocity impact loading. For this reason, herein, we conducted an experimental method with the self‐designed clamp to evaluate the influence of low‐velocity impact (LVI) at the compressed area nearby the bolt hole on the residual tensile properties of bolt joint GFRP laminates with various stacking sequences. After comparing the displacement‐force curves and failure modes of different bolt joints in tensile tests after LVI loading, the effect of LVI and the failure mechanism subjected to post‐impact loading are discussed in depth. Tensile properties show that the damage caused by impact has a significant effect on the performance of the composite. Under the condition of incident energy of 9 J and distance of 6 mm from the center of the bolt hole to the impact point, the ultimate tensile value of Ply‐A, Ply‐B, and Ply‐C samples are reduced by 32.3%, 34.6%, and 50%, respectively. This influence can also be confirmed by observing the failure morphology, describing the interlaminar behavior of the specimens varying stacking sequence, where a more serious interlaminar damage was identified at Ply‐C specimens. In addition, we also utilized the VIC‐2D device to record and analyze the strain of different ply stacking sequence specimens in the failure process. The result shows that all types of cases have the same initial failure mode of bearing, but various final failure modes.

Load-carrying capacity of hot-pressed thermoplastic composite joints

Abstract Composite joints have been commonly used in many industries such as aviation, aerospace, and automotive due to their advantages of being light and durable. Internal stresses may occur especially during the service life of these materials and decrease the load-carrying capacity of the joints. In this study, high density polyethylene (HDPE) and glass fiber reinforced polypropylene composite panels are used resorting to different combinations by using hot-pressing method as a single lap joint, and their mechanical properties are investigated under different temperatures, experimentally. Tensile tests were carried out at different temperatures in order to examine the temperature effect on load-carrying capacity of joints. Different bonding types of composites were compared to obtain the optimal joint configurations. The effect of low velocity impact on the failure response of the joints at impact energy levels of 5 and 10 J is also evaluated. From the tensile tests after impact treatment, it was concluded that transverse impact significantly decreased the load-carrying capacity of the single lap thermoplastic joints. Based upon the experimental results, it was concluded that HDPE–HDPE joints demonstrated higher tensile failure loads at 50 °C after transverse impact. Moreover, the tensile strength of all types of configurations decreased with increasing temperature.

Effect of low-velocity impact on mechanical property and fatigue life of DP590/AA6061 self-piercing riveted joints

The low-velocity impact behaviors of DP590/AA6061 self-piercing riveting (SPR) joints are studied at the impact energies of 5 J, 10 J, 20 J, 30 J, and room temperature (25 °C). The lap shear and fatigue tests, and the cross-sectional microscopies of joints are used to assess the mechanical property evolutions of the joints after low-velocity impact. The results show that the absorbed impact energies of SPR joints reach the critical value at an impact energy of 30 J, the exceeded impact energy causes crack failures in the sheets and decreases the interlocking performance of the joints. The static property and the absorbed energy of the SPR joints are reduced by 16% and 36% when the joints are impacted at 30 J, respectively. The low-velocity impacts do not change the failure forms of the joints, but significantly reduce the mechanical interlocking properties of the joints. The fatigue lives of the SPR joints are reduced due to low-velocity impact, and the impacted joints are more sensitive to cyclic loadings.

Effects of low-velocity impact on vibration behaviors of polyamide fiber-reinforced composites

Effects of low-velocity impact on vibration behaviors of polyamide fiber-reinforced composites

Effect of low velocity impact on residual compressive strength of stiffened panel with welding residual stress

Al-Li alloy stiffened panel is the main structural form of aircraft fuselage. Laser welding will produce welding deformation and residual stress, on the other hand, low velocity impact will also affect the residual bearing capacity of stiffened panel structure. In this study, the nonlinear finite element (FE) method is used to simulate the laser welding process of stiffened panel, and the welding residual stress is directly introduced into the subsequent impact after compression (CAI) process of stiffened panel. The effects of different impact positions and different impact energy on the residual CAI strength of stiffened panel are studied. The results show that the impact damage has the greatest effect on the residual compressive strength of stiffened panel when the punch impacts the stiffener, and the greater the impact energy is, the greater the influence is.

Experimental investigation of the effect of diameter upon low velocity impact response of glass fiber reinforced composite pipes

The GRP (Glass Reinforced Polymer) composite pipes produced by filament winding technique are used in many fields such as the transmission of pressurized chemical liquids, industrial liquids, oil and natural gas transmission and construction materials. GRP composite pipes may be subjected to low velocity impacts for various reasons both during installation and service. The impact on the GRP composite pipe wall may lead to some nonvisible damages such as matrix crack, fiber damage, delamination and inter-layer separation. Composite pipes suffered strength loss due to these damages caused by impact cannot support the expected strength values during service. Pipes with three different diameters (Ø54, Ø72 and Ø96 mm) were produced to investigate the damage caused by low velocity impact and to determine the effect of these damages on the strength losses of the composite pipe. In order to investigate the influence of low velocity impact damage, the produced pipes were subjected to impacts at the velocity of 1.5, 2, 2.5 and 3 m/s according to ASTM D 7136 and preliminary damage was formed. During low velocity impact tests, Force-Time, Force-Displacement and Energy-Time graphs were obtained and dynamic behavior of the pipes were examined. With the increase in diameter; it has been observed that the effect of low velocity impact is reduced and the damage after impact transformed into delamination damage rather than multiple damage.

Low velocity impact response and damages of GFRP composite tubes under room and cryogenic temperatures

In this paper, we have investigated the damages of glass fiber reinforced plastic (GFRP) composite tubes under the effect of low-velocity impact (LVI) at cryogenic environment conditions and room temperature. A GFRP composite tube consists of 6 layered E-glass/epoxy samples with a ± 55° winding angle, which produced by the filament winding method. Composite tubes either at room temperature or conditioned by liquid nitrogen at different temperature values (273 K, 223 K, 173 K, and 77 K) were impacted at 5, 7.5, and 10 J. Also, force-time and force-displacement graphs were plotted. The damaged regions of the samples were scrutinized. The damage areas of the GFRP composite tubes were smaller as the temperature decreased. However, the energy absorbed at low-temperature conditions was slightly higher than that absorbed in room temperature. Besides, no micro-cracks developed in the composite tubes after cryogenic conditioning.

Progressive damage modelling and fatigue life prediction of Plain-weave composite laminates with Low-velocity impact damage

This paper developed a fatigue-driven residual strength model considering the effects of low-velocity impact (LVI) damage and stress ratio. New fatigue failure criteria based on fatigue-driven residual strength concept and fatigue progressive damage model were developed to simulate fatigue damage growth and predict fatigue life for plain-weave composite laminates with LVI damage. To validate the proposed model, LVI tests of plain-weave glass fibre reinforced polymer 3238A/EW250F laminates were conducted, followed by post-impact constant amplitude tension–tension, compression-compression fatigue tests and multi-step fatigue tests. Experimental results indicate that the LVI damage degrades fatigue strength of plain-weave glass fibre composite laminate drastically. The load history also plays an important role on the fatigue accumulation damage of post-impact laminates. The new fatigue progressive damage model achieves a good agreement with fatigue life of post-impact laminates and is able to capture the load sequence effect, opening a new avenue to predict fatigue failure of composite laminates.

Analysis of fracture energy in drop weight tear testing of API X65 gas pipeline steel

In this research, the effect of low velocity impact (LVI) on different components of fracture energy of API X65 gas pipeline steel is investigated using drop weight tear test (DWTT) specimens. For this purpose, twenty one test specimens (arranged in seven similar test groups) were used. The LVI tests were carried out first on six test groups by releasing the machine hammer from different heights from 0.05 m to 0.3 m. Then, full fracture DWTTs were conducted on all seven test groups using 2 m drop height. The fracture energy of tested specimens and its different components were calculated from test data using an instrumented hammer. These were compared to similar energies of virgin test specimens. It was found that by increasing LVI energy, yield energy increased up to 26% due to work hardening. However, crack initiation energy decreased significantly (down to 48%) due to plastic deformation at crack tip and crack tip blunting. By considering energy consumption, a novel test technique was presented for exact determination of crack initiation point.

Effect of low velocity impact on hybrid composite pipes orientated with different helix angles – numerical method

In this study Finite Element Analysis (FEA) model is developed to understand the effect of low velocity impact on hybrid (Carbon/Glass/Epoxy) composite pipes which were wound using the filament winding technique in two different diameters. The results were compared with the existing experimental results and further validated FEA model was used to understand the effect of varying thickness and change of helix angle in the impact using ABAQUS tool. In this FEA design, composite pipe was modelled with the orientation of (CG90/CG60) for varying thicknesses (2.67mm, 4mm, 5.3mm and 6mm) and helix angles with variations as 15°, 30°, 45°, 60°, 75°, and 90° respectively. Hybrid pipe model was subjected to three different levels of impact energy namely as 20 J, 25 J and 30 J. Effect of impact studied in terms of force, deflection and energy absorbed by the specimen. The possibility of increasing in the energy absorption through increasing thickness and withstanding high impact forces and impact resistance decreasing with increase in the helix angle of orientation namely, as 15°, 30°, 45°, 60°, 75°, and 90° respectively was seen.

Impact damage tolerance of energy storage composite structures containing lithium-ion polymer batteries

Multifunctional composite structures that combine high load-bearing properties with electrical energy storage capacity have potential application in electric and hybrid powered cars, and therefore must be impact resistant in the event of collision. This paper examines the effect of low velocity impact on the damage, compression properties and energy storage capacity of composite laminates and sandwich composites containing an embedded lithium-ion polymer (LiPo) battery. The impact responses of a carbon fibre-reinforced epoxy (CFRP) laminate and a polymer foam core sandwich composite are investigated. The materials were impacted at different incident energy levels at the location immediately above the embedded battery. The battery at the impact location increased the impact energy absorption of both the laminate and sandwich composite due to its capacity to yield and plastically deform. Impact-induced damage reduced the compressive properties of the composite laminate and sandwich composite in part due to deformation, cracking and debonding of the battery. Low impact energy events (≤4 J) had negligible effect on the residual energy storage capacity of the LiPo battery, although higher energies (≥6 J) caused an internal short circuit due to excessive plastic deformation and crushing.

Electromechanical energy absorption, resonance frequency, and low-velocity impact analysis of the piezoelectric doubly curved system

In this research, electrically performance, vibration/resonance characteristics, low-velocity impact, and absorbed energy of the piezoelectric doubly curved panel on the viscoelastic substrate is carried out. For modeling the contact force between the structure and impactor, Hertz contact theory is presented. Hamilton’s principle and first-order shear deformation theory (FSDT) are presented for obtaining the governing and boundary condition equations of the structure under the low-velocity impact. Galerkin and Newmark solution procedures are presented for solving the governing equation in displacement, and time domains, respectively. This study's novelty is considering the effect of low-velocity impact on the electromechanical energy-absorption capability and resonance frequency of the piezoelectric doubly curved panel on the viscoelastic substrate. The results section is divided into three sections. The first one studied the impact of applied voltage and elastic parameter of foundation on the displacement field and absorbed energy of the structure during the time domain. The second one presents the influence of circumferential wave number, the thickness of the structure, and applied voltage on the current model's free and forced vibration characteristics under the low-velocity impact. In the third one, the influence of the elastic factor parameter of piezoelectric (c11/c12) and the velocity of the impactor on the indentation, contact force, absorbed energy in the panel, and indenter velocity are investigated in details. The golden result is that the curvature ratio (R1/a) of the doubly curved panel should be more than 3.8 because for R1/a less than 3.8, the structure encounters instability in response. As a desirable result for the designer, as the impactor velocity increases, the electrical panel's absorbed energy improves, and the maximum absorbed energy happens at the lower time of the impact process.

Effect of low-velocity impact on the strength and durability of bonded joint in hygrothermal environment

ABSTRACT The effect of low-velocity impact on the strength durability of adhesively bonded joints in hygrothermal environment was investigated in this study. Four different impact energies were applied during the low-velocity impact process, and the impacted joints were then subjected to hygrothermal exposure. The impact characteristics, residual strength, adhesive characteristics, and failure modes of tested samples were analyzed. The results indicated that the bonding strength and environmental durability of joints were greatly affected by the impact, initial damages caused by the impact decreased the joint strength and accelerated the moisture penetration in the hygrothermal exposure. The strength of the unimpacted joint was reduced by 5.51% after exposure, while the strengths of the impacted joints were reduced by 6.81, 7.69, 10.04% and 12.5%, respectively, for impact energies of 4 J, 8 J, 12 J and 16 J.

Piezoresistive detection of simulated hotspots and the effects of low velocity impact at the mesoscale in nanocomposite bonded energetic materials via multiphysics peridynamics modeling

The growth of hotspots within polymer bonded explosives can lead to thermal decomposition and subsequent initiation of the energetic material. An embedded structural health monitoring framework is proposed where carbon nanotubes are embedded within the polymer binder medium of polymer bonded explosives. The presence of the distributed carbon nanotube network enables the detection of hotspots through the analysis of the piezoresistive sensing response. The piezoresistive response correlates changes in the resistivity with changes in the mesoscale strain and damage distribution. The focus of the present study is on the assessment of the detection of hotspots at the mesoscale through analysis of the mesoscale thermo-electro-mechanical response via a multiphysics peridynamics modeling framework. The framework is also applied to assess the combined effects of thermal loading due to the hotspots with inertial effects due to low velocity impact loading. Prescribed hotspots were randomly seeded at various locations within the energetic material and modeled as regions with fast rising temperatures up to and beyond the point of thermal damage initiation. It has been found that the present model is able to detect the presence of hotspot dominated regions within the energetic material through the piezoresistive sensing mechanism. The influence of prescribed hotspots on the thermo-electro-mechanical response of the energetic material under a combination of thermal and inertial loading was observed to dominate the lower velocity impact response via thermal shock damage. In contrast, the higher velocity impact energies demonstrated an inertially dominated damage response, with the transition between the two damage types occurring at an impact energy around 3.75×105J/m3.

The effect of low-velocity impact on the flexural strength of E-glass/epoxy composite plates

E-glass/epoxy composite is very prone to small impact such as dropping tools or splash rocks, which can cause damage or degradation to E-glass/epoxy composite components. A progressive damage model for E-glass/epoxy composite in ABAQUS Explicit was developed in this study to numerically predict low-velocity impact (LVI) damage and residual strength of an E-glass/epoxy composite component. Hashin-Rotem criteria were used to define laminate damage initiation, and traction-separation law was used to define the cohesive region. LVI and four-point bending after the impact (BAI) of the woven E-glass/epoxy composite plates were simulated and compared with available experimental data in the literature. Good agreement was found between finite element analysis (FEA) predictions and the experimental results, which include the impact zone shape, as well as the load-deflection response and residual bending strength from the four-point bending tests.

Effect of Low Velocity Impact at Pre-Stressed Condition on Curved Glass-Carbon Composites Laminate

A curved composite panel is used in aircraft parts such as wings and engine cowling in order to improve their impact resistance to different types of impact loads. The effect of size reduction in the tensile pre-stress behaviour of low velocity impact on different materials such as glass and glass/carbon hybrid is examined in this paper. The effects of low velocity impact behaviour of two different pre-stressed curved laminates are taken for consideration and examined under impact loading. The objective of this research is to improve the efficiency of curved laminate by changing the hybrid composition such as glass/carbon with varied stacking sequence. The present studies using hybrid composition have shown that the load carrying capacity is higher in convex laminates while the damaged surface area in convex laminates is very less.

Single and repeated low-velocity impact response of E-glass fiber-reinforced epoxy and polypropylene composites for different impactor shapes

This study focuses on the effects of low-velocity impact (LVI) response of thermoset (TS) and thermoplastic (TP) matrix-based composites. In this study, the effects of the impactor shapes on the low-velocity impact response of the composite panels that produced from different matrix was investigated. Unidirectional E-glass fiber fabrics with an areal density of 300 g/m2 as reinforcement and epoxy matrix were used to produce TS composite. The vacuum-assisted resin infusion molding (VARIM) method was used to manufacture composite panels. The thermoplastic composites were manufactured with E-glass fiber-reinforced polypropylene prepregs. The tensile strength of TS matrix-based composites is higher than TP matrix-based composites that have the same fiber volume fraction. Despite being under the same impact energy, the TP specimens possess higher perforation threshold than TS specimens. The shape of the impactor significantly affected the perforation threshold. Besides, the impact number that caused perforation reduced dramatically in conical impactor. The repeated impact number that caused perforation is 36 for hemispherical (HS) impactor, but it is only 3 for conical impactor for polypropylene matrix-based composite. Moreover, a significant effect of fiber volumetric ratio on impact resistance was observed. The perforation threshold of glass fiber-reinforced polypropylene composites for 40% and 50% fiber volume fraction are 61 and 98 J, respectively. The perforation threshold of TP and TS specimens for HS impactor that has the same stacking sequence is 61 and 55 J, respectively.

Study upon the Damage Tolerance of Thick Sandwich Materials

Sandwich composite materials are widely used in various applications, due to their advanced flexibility in responding to special design requirements. This paper presents the evaluation of thick sandwiches, aimed to be imbedded in platforms of a green energy unit, accommodating storage water tanks. The evaluation of the damage tolerance was made having in view previous studies on similar materials and covered assessment of results obtained during low velocity impact tests and post-impact tests, aimed to establish the residual mechanical performance. Ways to increase the damage tolerance, by diminishing the invasive effect of low velocity impact, were also explored.

An investigation into the effects of fabric reinforcements in the bonding surface on failure response and transverse impact behavior of adhesively bonded dissimilar joints

Abstract The purpose of the current study is to evaluate the failure response and transverse impact behavior of adhesively bonded dissimilar single-lap composite joints fabricated by using fiber-reinforced polymer. The adherend materials utilized for the experimental tests were AA6082-T6 and glass fiber reinforced polymer (GFRP) in the form of thin sheets. The adhesive used was a warm to hot curing epoxy system (Araldite LY 1564 SP/Aradur 3487 BD) manufactured by Huntsman. In this study, some modifications were provided to enhance the failure response of single-lap composite joints. These modifications comprise the addition of different type and number of fabric reinforcements in the bonding surface. Based upon the test results, an increase of 33.6% in the failure load at room temperature is obtained for the joint fabricated by the addition of double-layer glass fabric reinforcement in the bonding surface. However, the failure load of all types of joint modifications decreases with the increasing tensile test temperature from room temperature to 75 °C. Similarly, tensile tests of the same specimen also resulted in double failure displacement by comparison with the adhesively bonded joint through only epoxy without any fabric reinforcement. The effect of low velocity impact on the failure response of the joints at the impact energy level of 2.5 J is also evaluated. From the tensile tests subsequent to impact treatment, it was found that the transverse impact significantly reduced the failure load of all types of joint modifications. However, the adopted modifications provided tensile failure loads over 1875 N and 1270 N for the joint fabricated by using double-layer carbon and glass fabric reinforcements, respectively.