scholarly journals Nonlinear Stress and Deformation Behaviour of Composite Sandwich Beams

2008 ◽  
Vol 13-14 ◽  
pp. 91-98 ◽  
Author(s):  
E.E. Gdoutos ◽  
I.M. Daniel
Keyword(s):  
Experimental Results ◽  
Core Material ◽  
Sandwich Beams ◽  
Stress Strain ◽  
Normal Stress Distribution ◽  
Nonlinear Load ◽  
Composite Sandwich ◽  
The Core ◽  
Nonlinear Stress ◽  
Load Displacement

The nonlinear load-displacement and normal stress distribution in composite sandwich beams made of unidirectional carbon/epoxy facings and PVC foam cores under bending was studied. The carbon/epoxy after an initial linear response exhibits a stiffening nonlinearity in tension and a softening nonlinearity in compression with the longitudinal strength in tension higher than that in compression. The foam core also presents a nonlinear stress-strain response. It was obtained that the load-displacement behaviour of the beam, after an initial linear part, is not linear. This behavior was modeled by an incremental strength of materials nonlinear analysis. The theoretical predictions were in good agreement with the experimental results. Furthermore, it was obtained that the neutral axis of sandwich beams under bending does not pass through the centroid of the cross section, but is displaced toward the tensile side of the beam. Experimental results by moiré measurements of the in-plane horizontal displacements of the core material corroborated the analytical predictions. These findings imply higher compressive and smaller tensile stresses in the core, than those predicted for facings with identical stress-strain behaviour in tension and compression, and should be taking into consideration in the failure analysis of sandwich beams.

A Study of Hybrid Composite Sandwich Beam

2019 ◽  
Author(s):  
Shah Alam ◽  
Guoqiang Li
Keyword(s):  
Finite Element ◽  
Finite Element Modeling ◽  
Experimental Results ◽  
Core Material ◽  
Sandwich Beams ◽  
Premature Failure ◽  
Element Modeling ◽  
Composite Sandwich ◽  
The Core ◽  
Linear Variable Displacement Transducer

Abstract This study presents the testing and numerical modeling results of composite sandwich beams. The sandwich beams are constructed from balsa wood in the core and high strength steel wire and E-glass fiber reinforced polymer composite in the facings. The testing of these beams is performed using a monotonic static four-point loading to failure in accordance with ASTM C393-00. Local strain distribution in the mid-span of the beams is obtained using strain gauges. Mid-span deflections of the beams are real-time measured using linear variable displacement transducer (LVDT). From the experimental results, flexural properties of the beams are calculated, including bending stiffness, bending strength, core shear strength, and facing modulus, core modulus, etc. The experimental results have shown that the beams have all failed in the compression zone by local buckling of the top face and shear of the core. The bottom skin does not exhibit any type of premature failure or distress. No bond failure of the composite in the tension zone is observed in any of the tested beams. Finite element modeling of the beam has been conducted using ANSYS. The mechanical properties of the skin and core material used in finite element modeling have been determined by testing of coupons. The predicted results are compared to experimental results, with a reasonable agreement.

Investigation of elastomeric foam response applied as core for composite sandwich beams through progressive failure of the beams

2017 ◽  
Vol 21 (2) ◽  
pp. 604-638
Author(s):  
AR Nazari ◽  
MZ Kabir ◽  
H Hosseini Toudeshky
Keyword(s):  
Finite Element ◽  
Carrying Capacity ◽  
Progressive Failure ◽  
Core Material ◽  
Foam Core ◽  
Sandwich Beams ◽  
Load Carrying Capacity ◽  
Composite Sandwich ◽  
The Core ◽  
Load Carrying

In this paper an elastomeric foam is applied as core for the composite sandwich beams and load carrying capacity, load–deflection response, and progressive failure are examined through experimental and finite element studies. The objective of this study is to assess the efficiency of elastomeric foam-cored sandwich (EFCS) beams relative to crushable foam-cored sandwich (CFCS) beams. The experimental program consists of two phases. In the first phase, some characterization tests are conducted on the constituent materials of the sandwich beams such as tension, compression, and shear tests on the foam and bending test on the composite beams utilized as skins. Then in the second phase, the performance of the sandwich beams is examined under bending conditions. The load carrying behavior of the sandwich beams is considered dependent on two main features of the constituent materials: (1) the hyperelastic behavior of the foam core and (2) the progressive damage of the composite skins. These characteristics are simulated by the finite element models. Due to elastomeric rather than crushable deformation of the applied foam as the core, the conventional damage modes of the CFCS beams associated to the brittleness of the core material are omitted through load carrying capacity of the EFCS beams. So in the recent sandwich beams by omission of the core failure modes and utilization of compressive residual strength of the top composite skin, considerable energy is absorbed prior to failure of the bottom composite skin. By simulation of the test specimens using FE models, the response of the foam applied as core for the sandwich beams through progressive failure of the beams is investigated. The results show that the elastomeric foam core can provide superior features for the sandwich components especially for the cases in which high energy absorption capacity is required.

Experimental investigations on the sandwich composite beams and panels with elastomeric foam core

2017 ◽  
Vol 21 (3) ◽  
pp. 865-894 ◽  
Author(s):  
AR Nazari ◽  
H Hosseini-Toudeshky ◽  
MZ Kabir
Keyword(s):  
Carrying Capacity ◽  
Sandwich Structures ◽  
Failure Mechanisms ◽  
Composite Beams ◽  
Core Material ◽  
Foam Core ◽  
Sandwich Beams ◽  
Load Carrying Capacity ◽  
The Core ◽  
Load Carrying

In this paper, the load-carrying capacity and failure mechanisms of sandwich beams and panels with elastomeric foam core and composite laminate face sheets are investigated. For this purpose, the flexural behavior of laminated composite beams and panels (applied as face sheets) is firstly investigated under three-point bending and central concentrated loads, respectively. Then, the same examination is conducted for the sandwich beams and panels, in which the proposed elastomeric foam is utilized as the core material. It is shown that the failure mechanisms which are associated to the core in the sandwich structures with crushable foams are not considered in the examined sandwich structures. The collapse of the sandwich specimens, examined here, is observed due to the failure of the skins in some steps. By multi-step collapse of these specimens via separately failure of the top and bottom skins, a considerable amount of energy is absorbed between these steps. Due to non-brittle behavior of the core material under loading, a large compression resistance is observed after failure of the top skin which led to the recovery of the load-carrying capacity in the sandwich beams. A similar behavior for the sandwich panels led to the increase of the ultimate strength after appearance of the failure lines on the top skin. The general outcomes of this investigation promise a good influence for the application of elastomeric foam as core material for sandwich structures.

scholarly journals PENGARUH TEBAL STYROFOAM CORE TERHADAP BERAT JENIS DAN KEKUATAN TEKAN KOMPOSIT SANDWICH MATRIKPOLYESTER DIPERKUAT SERAT SISAL DAN SERAT POHON PISANG

2012 ◽  
Vol 2 (1) ◽  
Author(s):  
S. Sinarep ◽  
Agus Dwi Catur
Keyword(s):  
Compressive Strength ◽  
Specific Gravity ◽  
Wood Products ◽  
Core Material ◽  
Sisal Fiber ◽  
Sandwich Composite ◽  
Composite Sandwich ◽  
The Core ◽  
Banana Tree ◽  
Core Thickness

Sandwich composite structure consisting of a core is flanked by two skin.  Therefore, the density of the composite sandwich are influenced by core composites material, the more light core the more lightweight composite produced. So also with the composite compressive strength is also very dependent on the core material. In this paper discussed the influence of core thickness on density and compressive strength of composite sandwich. Sisal fiber or  banana tree fibers that have been woven embedded in polyester composites to strengthen the skin. Composite core (Styrofoam) inserted between the two types of laminated composites to reduce weight and increase rigidity. The variation of the thickness of the core is applied in the manufacture of composites. Made of composite density was measured for specific gravity compared to wood or wood products on the market. Compressive strength of composite was characterized to determine the effect of core thickness on the compressive strength of composites.Research results show that the density of composite decreases with increasing thickness of  styrofoam core. Sandwich composite density is much smaller than the specific gravity of wood or wood products on the market.

Load-Carrying Characteristics of Foam Core and Joint Geometry in Sandwich Structures

2020 ◽  
Author(s):  
Jonas W. Ringsberg
Keyword(s):  
Structural Integrity ◽  
Side Wall ◽  
Core Material ◽  
Fe Model ◽  
Foam Core ◽  
Stress Concentrations ◽  
Production Time ◽  
Composite Sandwich ◽  
The Core ◽  
Load Carrying

Abstract Composite sandwich ships have laminated joints that contribute to a significant part of the ship’s weight. Their construction requires an extensive number of man-hours. There is great potential for weight and production-time-reduction through alternative joint designs. According to class rules, one is not allowed to benefit from the load-carrying capability of the core, i.e. the strength characteristics of the core shall be disregarded and geometry at the joint location is disregarded as well. The objective of the current investigation was to investigate the possibility of constructing a joint where the load-carrying capability of the foam core is accounted for, leading to a reduction in weight and production time. One specific joint in a 23 m composite sandwich catamaran was selected for study — a side wall-wet deck T-joint. This joint is considered to be crucial for the structural integrity of the current vessel. A global finite element (FE) model of the catamaran was designed and analysed in ANSYS. The loads and boundary conditions were applied to the global model according to DNV GL’s HSLC rules. Two local FE models of the joints (2D and 3D) were utilized for a parametric analysis with respect to structure response (stress concentrations and compliance with failure and fracture criteria). Finally, the results and conclusions from the study show the possibilities and advantages of incorporating the foam core material as a load-carrying member in joint design without compromising safety.

Failure and Deformation Modes of Sandwich Beams under Quasi-Static Loading

2010 ◽  
Vol 29-32 ◽  
pp. 84-88
Author(s):  
Lin Jing ◽  
Zhi Hua Wang ◽  
Long Mao Zhao
Keyword(s):  
Aluminum Foam ◽  
Failure Modes ◽  
Experimental Results ◽  
Sandwich Beams ◽  
Foam Material ◽  
Deformation And Failure ◽  
Structure Response ◽  
The Core ◽  
Bottom Face ◽  
Deformation Modes

In this paper the structure response of quasi-statically loaded sandwich beams made of aluminum skins with open-cell aluminum foam cores is investigated experimentally. The experimental programme was designed to investigate the deformation and failure modes of sandwich beams, so a large number of experiments have been conducted, and the experimental results are reported and discussed systematically. It is found that sandwich beams under quasi-static punching loads can fail in several modes: face yield, face wrinkling, core shear, the bottom face fracture and interfacial failure between the core and the faces. Moreover, the effects of face thickness, cell size of foam material on the failure and deformation modes were discussed. The experimental results are of worth to optimum design of cellular metallic sandwich structures.

Behavior of Steel Tube and Confined High Strength Concrete for Concrete-Filled RHS Tubes

2005 ◽  
Vol 8 (2) ◽  
pp. 101-116 ◽  
Author(s):  
Sumei Zhang ◽  
Lanhui Guo ◽  
Zaili Ye ◽  
Yuyin Wang
Keyword(s):  
High Strength Concrete ◽  
Concrete Strength ◽  
Compressive Load ◽  
High Strength ◽  
Steel Tube ◽  
Experimental Results ◽  
Stress Strain ◽  
Hollow Section ◽  
Strength Concrete ◽  
Nonlinear Stress

This paper presents an experimental study of the separated behavior of short ( L/H=3) high strength concrete-filled rectangular hollow section (RHS) tubes concentrically loaded in compression to failure. A total of 50 specimens were tested. Experimental results showed that the concrete strength influenced the failure pattern of the specimen. The height-to-breadth ratio of the rectangular tube (varying from 1.0 to 1.6) had no evident influence on the ultimate bearing capacity of the specimen. Then based on the experimental results, a numerical separation method was successfully used to separate the compressive load carried by the steel tube and the core concrete. The equivalent One-Dimensional nonlinear stress-strain models of the steel and the confined concrete were suggested, which can be used to determine the overall behavior of the high strength concrete-filled RHS tubes. The stress-strain models have been used to numerically analyze the behavior of high strength concrete-filled RHS tubes. The numerical results are compared with the experimental results and they agreed well with each other.

A Core Catcher Concept and First Experimental Results

2010 ◽  
Author(s):  
Hwan Yeol Kim ◽  
Kwang Soon Ha ◽  
Jong Hwan Kim ◽  
Seong Wan Hong ◽  
Jin Ho Song
Keyword(s):  
Sacrificial Layer ◽  
Water Injection ◽  
Experimental Results ◽  
Core Material ◽  
Test Facility ◽  
Concrete Wall ◽  
Water Storage Tank ◽  
The Core ◽  
Core Catcher ◽  
Retention Device

In a postulated core melt accident, if a molten core is released outside a reactor vessel despite taking mitigation actions, the core debris would relocate in the reactor cavity region and attack the concrete wall and basemat of the reactor cavity. This will potentially result in inevitable concrete decompositions and possible radiological releases. To prevent direct contact of the melt and basemat concrete of the cavity, a core catcher concept is suggested, which can passively arrest and stabilize the molten core material inside the reactor cavity. The core catcher system includes a retention device for the molten core material, a cooling water storage tank, and a compressed gas tank. Upon ablation of the sacrificial layer on top of the retention device while molten core material is discharged, a mixture of water and gas is injected from below. It is expected that a simultaneous injection of water and gas could prevent a possible steam explosion/spike. It could also suppress the rapid release of steam which might result in fast over-pressurization of the containment. A test facility for the core catcher using a thermite reaction technique for the generation of the melt was designed and constructed at KAERI. The first series of tests were performed by using a mixture of Al, Fe2O3, and CaO as a stimulant. As a first try, only water was injected from the bottom of the melt through five water injection nozzles when the melt front reached the water injection nozzles. In this paper, the core catcher concept and the related provisions are suggested. A description of the test facility for the core catcher, the thermite composition, and the methods of experiment is included. The first experimental results with only water injected from the bottom of the melt are discussed.

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