Effect Of Low Velocity Impact Research Articles

Parametric Studies and Numerical Analysis of Low Velocity Impact on Smart Hybrid Composite Laminates

To evaluate the effect of low velocity impact on composite plate using nonlinear explicit finite element software LS-DYNA software. The theoretical basis of the present finite element model is verified by analyzing impact-loaded laminated composite plate previously been studied through analytical. The study of hybrid composite plates are carried were the SMA (shape memory alloy) are used in between the plies to increase the resistance. Also parametric studies were done to find the importance of the Mesh. The present numerical approach is successfully demonstrated through comparisons between experimentally-measured and computed force-time histories for impact of carbon fiber-reinforce plastic (CFRP) plates. Parametric studies are also conducted by varying Mesh results obtained are correlated with the results in the published literature.

Simulation of Low Velocity Impact Test on Carbon/Epoxy Composite Plates

Composite materials that have low weight and high strength properties are currently one of the promising materials for a vehicle’s body. However, the effect of low velocity impact on composite may cause failure through matrix cracking, fibre breakage and delamination which may reduce the structure strength. Low velocity impact can be analysed either by experimentation or numerical simulation. Numerical simulation which is also known as finite element analysis can show the degradation of the composite structure properties after an impact loading condition without doing any experimentation. Thus, in this paper, LS-DYNA is the finite element analysis software that is used to simulate a low velocity impact on composite structures.

An empirical modified fatigue damage model for impacted GFRP laminates

The aim of the present paper is to evaluate the residual strength of GFRP laminates following a low-velocity impact event under cyclic loading. The residual strength is calculated using a linear fatigue damage model. According to an investigation into the effect of low-velocity impact on the fatigue behavior of laminates, it seems laminate fatigue life decreases after impact. By normalizing the fatigue stress against undamaged static strength, the Fatigue Damage parameter “FD” is presented with a linear relationship as its slope which is a linear function of the initial impact energy; meanwhile, the constants were attained from experimental data. FD is implemented into a plane-stress continuum damage mechanics based model for GFRP composite laminates, in order to predict damage threshold in composite structures. An S–N curve is implemented to indicate the fatigue behavior for 2mm thickness encompassing both undamaged and impacted samples. A decline in lifespan is evident when the impact energy level increases. Finally, the FD is intended to capture the unique GFRP composite characteristics.

Explicit finite element analysis to predict impact damage response of osteoporosis hip bone

Hip fractures due to sideways falls are a worldwide health problem, especially amongst elderly people. The force experienced by the proximal femur during a fall, and therefore hip fracture, is significantly dependent on density, thickness and stiffness of the body during impact. The process of fracture and healing can only be understood in terms of the structure and composition of the bone and also its mechanical properties. Bone fracture analysis investigates the prediction of various failure mechanisms under different loading conditions. An accurate explicit finite element method will assist scientists and researchers to predict the impact damage response of bone structures. In this paper, the effect of low velocity impact on the osteoporotic hip in ageing people will be studied in LSDYNA. The first part aims to create a three-dimensional (3D) reconstruction and registration of semi-transparent computed tomography scan image data using Simpleware software. In the second part, the effect of cortical thickness and impact velocity on the energy absorption of the hip during a fall will be investigated on a 3D model using the latest techniques. The critical impulse loading of the hip will be the benchmark to improve the design of safety instruments and consequently the well-being of elderly people.

Compression after Impact Performance of Composite Stiffened Panels

Composite stiffened panels are widely used in the modern aircraft structure with the advantages of light weight, structural efficiency and good crack performance. But the stiffened panels have poor performance at thickness direction, especially for low-velocity impact. First of all, compressive tests were investigated and analyzed for two types of composite stiffened panels, which are integrated specimens and post-impact specimens. And the effect of low-velocity impact to the supporting capacity of composite stiffened panels was researched. Secondly，the finite element model was established to simulate the CAI (Compression After Impact)strength with the equivalent hole method. It is found that the analyze results match the experimental results well. According to the experimental results, structural damage and the maximum load caused by impact energy are scattering. Then the imperfect factors were introduced to reflect the initial imperfection, namely the initial deflection at thickness direction. The effect of different imperfect factors to the maximum load was discussed.

Residual Strength and Failure Criterion of PP Thermoplastic Honeycomb Sandwich Subjected to Low Velocity Impact

This paper presented the effect of constituent materials on impact damage and strength reduction of sandwich structure, composed of laminated woven E-glass facesheets and polypropylene thermoplastic honeycomb core. Effect of low-velocity impact was the main interest in a variety of layered configurations. Compression after impact (CAI) has been carried out to determine the residual strength of impacted sandwich structures. Three different thicknesses of core of 20, 40 and 60mm subjected to three different levels of impact energy of 15, 30 and 45J were investigated. Impact response of the panel was recorded and analyzed in terms of peak load, indentation, energy absorbed and time. A profile analysis using optical 3D surfaces profiler was carried out to attain the indentation depth and damage area of the samples. The tested samples were then sectioned into halves to capture the failure mode or damaged sequence of the polypropylene thermoplastic honeycomb core. The dominant failure modes of the core indicated that polypropylene thermoplastic honeycomb core is a high strength material which can absorb higher impact energy and retain a higher degree of structural integrity.

The effect of low-velocity impact on the fatigue life of Sandwich composites

Impact properties and fatigue properties of sandwich composites after impact are addressed. Specifically, the low-velocity impact resistance of carbon fiber faced sandwich composites and how the fatigue life is affected is studied. Two and four layer face sheet carbon fiber sandwich composite samples with foam filled honeycomb core were impacted in a low velocity drop tester at 10, 20, and 30 J with varying masses and velocities of the impactor. After impact the area of damage is determined using ultrasonic techniques. The fatigue life is then determined and compared to the fatigue life of non-impacted samples in a four point bend test. At all impact energies the impactor completely penetrated the front face of the sample. At 20 and 30 J the impactor also penetrated the back face. The 30 J caused a larger penetration area where as the 20 J caused more delamination of the back face. Two different densities of foam were used for the two layer samples. The two layer high density sample failure was changed from in shear for the virgin materials to bending for the impacted samples. This shows that penetrating the top face has an affect on the fatigue properties of the two layer samples. The fatigue life of the four layer and two layer low density samples does not appear to be affected by the impact.

Effect of low-velocity impact on the residual strength of composites

Effect of low-velocity impact on the residual strength of composites