Quasi-static Perforation Research Articles

The influence of strain-rate on the perforation resistance of fiber metal laminates

The rate-sensitivity of a range of fiber metal laminates (FMLs) has been investigated though split Hopkinson bar, quasi-static perforation and low velocity impact tests. Initial attention focused on assessing the rate-sensitivity of the constituent materials, that is the glass fiber reinforced epoxy and the three aluminum alloys. This was followed by a series of perforation tests on multilayer configurations.It has been shown that both the composite and the aluminum substrates exhibit a low degree of rate-sensitivity, with both the tensile strength and the perforation energy increasing slightly in passing from quasi-static to dynamic rates of loading. Similarly, FMLs based on combinations of the composite and metal constituents exhibit a low degree of rate-sensitivity, with the impact perforation energy and the maximum impact force being only ten to fifteen percent higher than their quasi-static values. An examination of the cross-sections of the failed laminates indicated that the failure processes were similar at both quasi-static and dynamic rates of strain. Also, similar levels of plastic deformation, fiber fracture and delamination were observed at both rates. Finally, it has been shown that the energy to perforate the various FMLs is directly related to the aggregated perforation energies of their constituent parts.

고속충격을 받는 Carbon/Epoxy 복합재 적층판의 충격체 질량손실을 고려한 흡수에너지 예측

본 논문에서는 Carbon/Epoxy 복합재 적층판에 대하여 실사격 실험을 수행하였으며, 복합재 적층판의 흡수에너지를 예측하기 위한 개선된 방법을 제시하였다. 고속충격실험 과정에서 충격체의 질량손실을 고속카메라를 통하여 거시적으로 확인하였으며, 따라서 이를 고려하여 복합재 적층판의 흡수에너지를 계산하였다. 고속충격을 받는 복합재 적층판의 흡수에너지를 예측하기 위한 모델을 제시하였으며, 복합재 적층판의 흡수에너지는 크게 정적에너지와 동적에너지로 분류하였다. 정적에너지 계산은 섬유의 파손과 정적 탄성에너지와 관련 있는 준정적 관통실험식을 통해 구한 관통에너지를 사용하였다. 동적에너지는 변형되는 시편의 운동에너지와 손실된 파편 질량들의 운동에너지로 나뉠 수 있다. 최종적으로 충격체 질량손실을 고려하여 예측된 흡수에너지와 실험결과를 비교/분석하였다. In this paper, we conducted high velocity impact test for Carbon/Epoxy composite laminates and proposed advanced method for predicting the absorbed energy of composite laminates. During high-velocity impact test, we discovered loss of projectile mass macroscopically using high speed camera, thus we calculated the absorbed energy of composite laminates by taking loss of projectile mass into account. We proposed a model for predicting the absorbed energy of composite laminates subjected to high-velocity impact, the absorbed energy was classified into static energy and dynamic energy. The static energy was calculated by the quasi-static perforation equation that is related to the fiber breakage and static elastic energy. The dynamic energy can be divided by the kinetic energy of deformed specimen and fragment mass. Finally, the predicted absorbed energy considering loss of projectile mass was compared with experimental results.

고속 충격을 받는 Carbon/Epoxy 복합재 적층판의 흡수 에너지 예측에 대한 실험적 고찰

ABSTRACT: The evaluation and prediction for the absorbed energy, residual velocity, and impact damage are the keythings to characterize the impact behavior of composite laminated panel subjected to high-velocity impact. In thispaper, the method to predict the residual velocity and the absorbed energy of Carbon/Epoxy laminated panelsubjected to high velocity impact are proposed and examined by using quasi-static perforation test and high-velocityimpact test. Total absorbed energy of specimen due to the high-velocity impact can be grouped with static energy andkinetic energy. The static energy are consisted of energy due to the failure of the fiber and matrix and static elasticenergy, which are related to the quasi-static perforation energy. The kinetic energy are consisted of kinetic energy ofmoving part of specimen, which are modelled by three modified kinetic model. The high-velocity impact test wereconducted by using air gun impact facility and compared with the predicted values. The damage area of specimenwere examined by C-scan image. In the high initial impact velocity above the ballistic limit, both the static energy andthe kinetic energy are known to be the major contribution of the total absorbed energy. 초록

정적압입 관통 실험을 이용한 복합재 적층판의 고속충격 탄도한계속도 예측

The ballistic limit of Carbon/Epoxy composite laminates with the finite effective area are predicted by using the quasi-static perforation test and semi-empirical formula. The perforation energy were calculated from force-displacement curve in quasi-static perforation test. Also, the actual ballistic limit and penetration energy were obtained through the high-velocity impact test. The quasi-static perforation test and high-velocity impact test were conducted for the specimens with 3 different effective areas. In the high-velocity impact test, the air gun impact tester were used, and the ballistic and residual velocity was measured. The required inputs for the semi-empirical formula were determined by the quasi-static perforation tests and high-velocity impact tests. The comparison between semi-empirical formula and high-velocity impact test results were conducted and examined. The ballistic limits predicted by semi-empirical formula were agreed well with high-velocity impact test results.

Low-velocity perforation behavior of composite sandwich panels with aluminum foam core

Perforation response and failure of sandwich panels with composite face sheets and aluminum foam core are investigated experimentally in this paper. Quasi-static perforation and low-velocity impact tests are carried out by using a material test system and a drop weight machine, respectively. The load-displacement response, energy absorption and energy-absorbing effectiveness of sandwich panels are obtained and compared for quasi-static and impact tests. Effects of some key parameters on the overall energy absorption behavior of the panels are explored, such as impact energy, face sheets and core thickness, core density and indenter nose shape.

Effect of Nanoclay on Quasi Static Perforation of Thin-walled Polymer Composite Laminates

In this study, the penetration and perforation performance of nanoclay reinforced unsaturated polyester resin/fibreglass nanocomposite laminates have been investigated via quasi-static indentation tests using ahemispherical nose indenter. Unsaturated polyester resin (UP) was mixed with 1.5 and 3 wt.% nanoclay using a homogenizer stirrer to prepare a homogeneous mix. UP reinforced nanocomposite was then utilized to manufacture 150 × 150 mm2 laminated composite panels using 400 g/m2 glass fibre woven roving via a hand lay-up process. X-ray diffractometry, transmission electron microscopy analysis, energy-dispersive X-ray (EDXA) analysis and measurement of viscosity changes in the liquid state resin confirmed the exfoliation and the intercalation of the nanoclay by the unsaturated polyester resin system used. Quasi-static perforation tests were conducted using a surface-hardened steel indenter with a hemispherical tip at 5 and 500 mm/min load rates on nanocomposite laminated plates. Measurement of the quasi-static force as a function of indenter displacement for all the specimens showed four distinct regions, namely penetration, perforation, exit and residual frictional force. The results indicated a clear role being played by the nanoclay filler as a secondary reinforcement, in terms of higher energy absorption in all four regions.

Impact perforation of sandwich panels with Coremat®

Analytical solutions for the quasi-static and low-velocity perforation of sandwich panels with woven roving E-glass/vinyl ester facesheets and Coremat were derived. A multi-stage perforation process involving delamination, debonding, core shear fracture and facesheet fracture was used to predict the quasi-static failure load and ballistic resistance of the panel. The high core-crushing resistance and damping of the Coremat resulted in rupture of the distal facesheet before the incident facesheet during panel perforation because they limited the amount of local indentation compared with global panel deformation. Analytical predictions of the quasi-static load-deflection response and the dynamic contact force history were within 10% of the test results.

Quasi-static perforation of thin aluminium plates

This paper presents an experimental and numerical investigation on the quasi-static perforation of aluminium plates. In the tests, square plates were mounted in a circular frame and penetrated by a cylindrical punch. A full factorial design was used to investigate the effects of varying plate thickness, boundary conditions, punch diameter and nose shape. Based on the results obtained, both the main and interaction effects on the maximum force, displacement at fracture and energy absorption until perforation were determined. The perforation process was then computer analysed using the nonlinear finite element code LS-DYNA. Simulations with axisymmetric elements, brick elements and shell elements were conducted. Quasi-static, isothermal versions of the Johnson–Cook constitutive relation and fracture criterion were used to model the material behaviour. Good qualitative agreement was in general found between the experimental results and the numerical simulations. However, some quantitative differences were observed, and the reasons for these are discussed.

A new damage index to monitor the range of the penetration process in thick laminates

A damage variable (damage degree DD) representing the ratio between the absorbed energy and the impact energy was introduced in 1998 by Belingardi and Vadori to assess damage accumulation caused by low velocity impacts. More recently, repeated impact tests carried out on thick laminates pointed out the significance and extent of the penetration process in thick laminates, which the DD is unable to monitor as, by definition, it reaches the value of one at penetration to remain unchanged over the entire penetration process. In the present paper, a new damage variable (damage index DI) is proposed to overcome shortcomings of the DD with respect to thick laminates. By introducing the displacement of the impactor into the definition of the DI, the depth of the penetration process is taken into account. Normalization by the displacement of the quasi-static perforation test allows for a non-dimensional damage variable which is shown to reach the value of one at perforation. Validity of the approach is proven against impact data obtained for different fibre-matrix architectures and laminate thickness. Results show that the DI can effectively differentiate between penetration and perforation thresholds, increasing monotonically within the range of the penetration process. In particular, the DI is shown to increase linearly with the impact energy up to penetration and to rise quite abruptly within the range of the penetration process. Results for repeated impact tests prove that at first the DI increases quite linearly impact after impact, owing to a steady accumulation of damage. A few impacts before penetration a sudden rise in the DI value points out a change in the rate of damage accumulation.

Out-of-plane deformation measurements of an aluminium plate during quasi-static perforation using structured light and close-range photogrammetry

An optical system using structured light and close-range photogrammetry for full-field continuous measurements of the out-of-plane deformation of a metal plate loaded at its centre by a moving punch is presented. The system is applicable both for quasi-static and dynamic loading conditions, but in this paper focus will be on the former. In the tests, a square AA5083-H116 aluminium plate is mounted in a circular frame and penetrated from above by a cylindrical punch, while the out-of-plane deformation is observed from below. A fringe pattern is projected on the target plate surface and recorded by a camera (or more than one if required). The changing fringe positions on the plate surface during perforation are then computer processed to give topography information of the out-of-plane deformation. This paper is divided into three major parts. First, the optical technique is presented with a description of the applied method, image analysis procedures, calibration of the system and estimation of accuracy of the acquired data points. The experimental set-up is then presented, and some results from a typical test where a 5 mm thick plate with free-span diameter of 500 mm is perforated by a 20 mm diameter blunt-nose punch are given. Finally, numerical simulations of the perforation process are carried out using the non-linear finite element code LS-DYNA. The numerical predictions are compared with the experimental observations and the applicability of the experimental method is discussed based on the obtained results.

Evolution of Failure Mechanisms in 2D and 3D Woven Composite Systems Under Quasi-Static Perforation

Evolution of Failure Mechanisms in 2D and 3D Woven Composite Systems Under Quasi-Static Perforation

Evolution of Failure Mechanisms in 2D and 3D Woven Composite Systems Under Quasi-Static Perforation

The effects of reinforcement geometry, in 2D and 3D woven fabric-reinforced composites, on the progression of damage and perforation failure at quasi-static loading rates (10-80 mm/s) are investigated. The broad classes of glass-fiber-reinforced systems that were examined include 2D plain-woven laminates, 3D orthogonally woven monolithic systems, and 3D orthogonally woven laminates. The experimental results indicate that the 3D laminates consistently had greater damage tolerance than the 2D laminates and the 3D monolithic composites. The enhanced damage tolerance of the 3D systems is due to unique energy absorption mechanisms, which involve the crimped portion of z-tows.

Study on impact perforation fracture mechanism in PMMA

Many studies on the hypervelocity impact problem in metallic materials have been conducted [1±3]. In these studies, rail guns, powder guns and light gas guns are used to launch projectiles. The correlation of target fracture morphology, absorbed energy, the penetration depth, and the crater diameter=volume with impact velocity is investigated. In the present study, polymeric materials are used as target material. The objective of the present study is to examine the fracture mechanism of polymeric materials by high velocity impact tests and quasistatic perforation tests. A target material is polymethylmethacrylate (PMMA). The target plate sizes are 115 mm3 115 mm and 214 mm 3 214 mm. Thickness of target specimens, t, are 1, 3, 5 and 10 mm. The target specimens are ®xed between two plates with circular holes. The diameters of the holes, D, are 100 mm and 200 mm. The high velocity impact tests and quasi-static perforation tests are impact test and perforation test into a ®xed circular plate. In high velocity impact tests, the experimental apparatus is composed of an air compressor and an air gun. Stainless and PMMA spherical projectiles, whose diameter is ,11 mm are launched by impact testing machine at various velocities up to 200 m sy1. In quasi-static perforation tests, the target specimen is perforated by a steel bar having a spherical head whose diameter is 10 mm. The tests are performed by using a universal testing machine. The cross head speeds are 0.5, 5.0 and 50.0 mm miny1. In high velocity impact tests, four typical fracture forms of targets and PMMA projectiles, respectively, were veri®ed. Fracture forms of targets are de®ned as ricochets, cracks, breaks and perforates. Those for projectiles are de®ned as intact, cracked, broken and shattered. Fig. 1 shows a ballistic phase diagram which indicates the relationships between the impact velocity and the fracture morphology of targets and projectiles. Fig. 2 shows the relation between impact velocity and perforated hole area. It is found that the hole area becomes similar to the maximum section area of the projectile at impact velocities above a certain value. For impact velocities below 100 m sy1, the perforation fracture is dominated by bending deformation. For impact velocities above 100 m sy1, bending deformation is very small before the projectile perforates the target. Fig. 3 shows typical load±displacement curves obtained by quasi-static perforation tests (D ˆ 100 mm, t ˆ 1 mm). It is seen that in this range of

高分子材料の衝撃貫通破壊について

High velocity impact tests are conducted by launching spherical stainless steel and PMMA projectiles into thin PMMA plate targets at various velocities. Ballistic phase diagrams are obtained which indicate the fracture behavior in targets and projectiles. Quasi-static perforation tests are also performed. The fracture surfaces in targets are examined microscopically.