Low Velocity Impact Phenomena Research Articles

The Effects of Initial In-Plane Loads on the Response of Composite-Sandwich Plates Subjected to Low Velocity Impact: Using a New Systematic Iterative Analytical Process

A new systematic iterative analytical procedure is presented to predict the dynamic response of composite sandwich plates subjected to low-velocity impact phenomenon with/without initial in-plane forces. In this method, the interaction between indenter and sandwich panel is modeled with considering the exponential equation similar to the Hertzian contact law and using the principle of minimum potential energy and the energy-balance model. In accordance with the mentioned procedure and considering initial in-plane forces, the unknown coefficients of the exponential equation are obtained analytically. Accordingly, the traditional Hertzian contact law is modified for use in the composite sandwich panel with the flexible core under biaxial pre-stresses. The maximum contact force using the two-degrees-of-freedom (2DOF) spring-mass model is calculated through an iterative systematic analytical process. Using the present method, in addition to reducing the runtime, the problem-solving process is carried out with appropriate convergence. The numerical results of the analysis are compared with the published experimental and theoretical results. The effects of some important geometrical and physical parameters on contact force history are examined in details.

Numerical study on the low-velocity impact response of ultra-high-performance fiber reinforced concrete beams

The material and structural behaviors of Ultra High-Performance Fiber-Reinforced Concrete (UHP-FRC) under a high strain rate loading are different than a quasi-static loading condition. Though, UHP-FRC has very high compressive strength compared to conventional concrete, the failure strain of UHP-FRC is not enough to withstand large plastic deformations under high stain rate loading such as impact and blast loading. Due to the high cost of large-scale experimental research of structural elements under impact loading, modeling of UHP-FRC girders using computer aided program has become a need. Hence, this study aims to develop a finite element model of UHP-FRC to simulate low-velocity impact phenomenon. The responses obtained from the numerical study are in good agreement with the experimental results under impact loads. Five different types of UHP-FRC beams were simulated under impact loading to observe the global and local material response. The key parameters investigated were the reinforcement ratio (ρ), impact load under various drop heights (h), and the failure phenomena. It was observed that higher reinforcement ratio showed better deflection recovery under the proposed impact. Also, for a specific reinforcement ratio, the maximum deflection increases approximately 15% when drop height decreases from 100 mm to 25 mm. Moreover, the applicability of concrete damage plasticity model for impact loading is investigated. The results also provide recommendations for predicting the location of the local damage in UHPFRC beams under impact loading.

Dynamic response of laminated composite beam reinforced with shape memory alloy wires subjected to low velocity impact of multiple masses

The response of laminated hybrid composite beam with embedded shape memory alloy wires subjected to impact of multiple masses is analytically investigated. Two degree of freedom spring-mass system and Fourier series are used in order to study the low velocity impact phenomenon on the resulting hybrid composite beam. A linearized contact law is chosen to calculate the contact force history. The effect of pseudo elasticity of wires as well as the recovery stresses generated in shape memory alloy wires due to shape memory effect is investigated. The beam is subjected to impactors with various masses, radii, and initial velocities. Impacts are occurred on the top and/or bottom surface of the beam. The effects of volume fraction of shape memory alloy wires, location of embedded wires, location of impacts and pre-strain in shape memory alloy wires on the contact force history and the deflection curve of the beam are investigated. The obtained results illustrated that embedding shape memory alloy wires in the laminated composite beam caused the deflection of the beam to occur more local at the points of impact, in comparison with the beams without shape memory alloy wires. Moreover, embedding 0.2 volume fraction of the shape memory alloy wires reduced the maximum deflection of the beam subjected to impact of 2 impactor masses by 57% and 3 impactor masses (on both sides) by 12%. Pre-straining the wires caused more reduction in deflection of the beam under impact loading.

Numerical study of the structural behaviour of impacted composite laminates subjected to compression load

Composite materials allow all the benefits which a high specific strength involves, in a design process their application involves many critical problems. Currently, these problems, such as environmental conditions, notch sensitivity, damaging under low velocity impacts, are taken into account by means of the application of conservative design safety factors regarding the ultimate tensile strength. In order to try to reduce these safety factors, this work aimed to study and to understand the impact damage growing mechanisms due to compression loads. To this purpose, compression tests have been experimentally performed on composite panels, which have been previously subjected to low velocity impact phenomena, considering impact energies of 6 J, 10 J and 13 J respectively. Moreover, numerical model able to simulate Low Velocity Impacts (LVI) and Compression After Impacts (CAI) onto CFRP panels is proposed. A single explicit finite element analysis has been carried out by using the Abaqus® finite element code; the need to build a numerical model, which allows simulation in only one analysis both LVI and CAI steps, depends on the difficulty to import the impact damage distribution into a separate compression analysis. In fact, in only one analysis the compression step can occur directly onto the impacted plate, which allows to consider the effective impact damage distribution as the starting configuration for quasi static analysis under operating loads.

Low velocity transverse impact response of functionally graded plates with temperature dependent properties

In this paper, a simple computational procedure based on classical plate theory and an analytical spring–mass model representing the contact behavior between the impactor and the plate are adopted to study the low velocity impact phenomenon of functionally graded plate included the temperature dependent properties of the plate. All mechanical properties of FG plate are temperature dependent vary continuously along the thickness according to the volume fraction of constituents by power-law, sigmoid, or exponential functions. Interaction between the impactor and the FG plate is modeled with a system having two-degrees-of-freedom, consisting the spring–mass (SM). The present systematic analytical analysis yields the analytic functions describing the history of contact force as well as the deflections of the impactor and the plate in the transverse direction. The analytic force function developed on the basis of SM model, can be used for the contact force between the impactor and the plate. The numerical results of the analysis are compared either with the available experimental and theoretical results in the literature or the presented FE model by ABAQUS code. The effect of temperature and types of defined function of FG material on contact force, deflection, maximum indentation and the stresses are investigated.

Analysis and optimization of smart hybrid composite plates subjected to low-velocity impact using the response surface methodology (RSM)

Optimization of the volume fraction, the orientation and the through thickness location of the shape memory alloy (SMA) wires was used in order to minimize the maximum transverse deflection of the hybrid composite plate during the low-velocity impact phenomena. The prediction of optimal conditions of good geometrical properties of SMA wires in smart hybrid composites plays an important role in process planning. The present work deals with the study and development of a verified strict model for smart composite plate deflection, which embedded with the SMA wires, using response surface method (RSM). This method helped us to estimate deflection ratio as a mathematical function of the main process planning parameters. The experimentation was carried out with the first-order shear deformation theory, the Fourier series method and solving analytically the system of governing differential equations of the plate. The interaction between the impactor and the plate also modeled with a system having two-degrees-of-freedom, consisting of springs-masses. A nonlinear mathematical model, in terms of the volume fraction and layer sequence (the orientation and the through thickness location) of the SMA wires was delivered. The results indicated that the volume fraction is a more important factor affecting the optimization and the design process of the structures.

Response of composite sandwich panels with transversely flexible core to low-velocity transverse impact: A new dynamic model

A new computational procedure based on improved higher order sandwich plate theory (IHSAPT) and two models representing contact behavior between the impactor and the panel are adopted to study the low velocity impact phenomenon of sandwich panels comprising of a transversely flexible core and laminated composite face-sheets. The interaction between the impactor and the panel is modeled with the help of a new system having three-degrees-of-freedom, consisting of spring–mass–damper–dashpot (SMDD) or spring–mass–damper (SMD). The effects of transverse flexibility of the core, and structural damping are considered. The present analysis yields analytic functions describing the history of contact force as well as the deflections of the impactor and the panel in the transverse direction. In order to determine all components of the displacements, stresses and strains in the face-sheets and the core, a numerical procedure based on improved higher order sandwich plate theory (IHSAPT) and Galerkin's method is employed for modeling the layered sandwich panel (without the impactor), while the analytic force function developed on the basis of SMDD or SMD model, can be used for the contact force between the impactor and the panel. The contact force is considered to be distributed uniformly over a contact patch whose size depends on the magnitude of the impact load as well as the elastic properties and geometry of the impactor. Various boundary conditions for the sandwich panel have also been considered. Finally, the numerical results of the analysis have been compared either with the available experimental results or with some theoretical results.

A Study of Impact Response of Composite Pipe

The objective of this study was to gain a better understanding of the low-velocity impact phenomena of composite pipe. The focus was on test method development, and material and damage characterization. A drop weight tower tester was designed in this investigation. The dynamic tests were conducted using three different impactor geometries, velocities, and masses. It was found that the damage was localized and on the outer surface of the pipe in the case of the conical and wedge tip impactors. On the other hand, the damage zone was larger than the impact zone for the hemispherical impactor, and cracks were first seen within the inner surface of the pipe. This implies that the hemispherical tip impactor caused more damage to the pipe than the conical or wedge tips. The energy absorbed slightly increased with an increase in velocity or in mass. The contact period for the conical impactor was the longest. The velocity and mass of the impactor had only a slight effect on that period. The wedge impactor generated the largest peak force. The energy absorbed by the two composite pipes under low-velocity impact was studied. The specimen-1, Derakane 411-45 resin with less glass fiber, seemed to absorb more energy compared to the specimen-2, Derakane 470-36 resin with more glass fiber. In addition, the specimen-2 exhibited a slightly higher maximum impact force. Therefore, impact response is sensitive to fiber content.