X-cor夹层结构的剪切模量实验与分析

通过力学分析得到考虑Z-Pin拉压受力情况的X-cor夹层结构剪切模量的解析式,并通过剪切刚度实验值和理论值的对比分析,得到考虑刚度折减系数M的修正理论公式。结果表明:加载过程中,Z-Pin从面板拔出是剪切刚度折减的原因。通过缩小Z-Pin长度的差异及提高Z-Pin从面板拉脱力的大小增大剪切刚度折减系数M,进而提高夹层结构的剪切刚度。     

X-cor夹层结构压缩模量有限元分析

通过两种有限元模型的对比,提出了符合实际的X-cor夹层结构压缩模量有限元计算模型,利用大型有限元软件ANSYS对其压缩模量进行了数值计算,得到了X-cor夹层结构的应力场和压缩模量.研究了Z-pin半径、密度、植入角度和体积分数的改变对模型压缩模量的影响.结果表明:X-cor夹层结构压缩模量随Z-pin植入角度增加而减小,随Z-pin半径、密度和体积分数增加而增加,且与Z-pin体积分数呈线性关系,改变Z-pin半径与改变Z-pin密度对X-cor夹层结构压缩模量影响是等效的.通过有限元模型的计算,得到了X-cor夹层结构参数对其压缩模量的影响规律,验证了所提有限元模型的合理性.     

X-cor夹层结构的力学性能试验研究

X-cor夹层结构比强度高,比刚度大,有望取代传统蜂窝夹层结构作为航空航天器的主承力结构材料。采用真空固化成型工艺,通过改变Z-pin的植入参数制备了X-cor夹层结构,研究了Z-pin植入角度、植入间距和直径对其平压、剪切和拉伸性能的影响。研究结果表明,Z-pin的植入参数对X-cor夹层结构的力学性能影响显著。随Z-pin植入角度的增加X-cor夹层结构的平压性能降低,剪切性能增强,拉伸模量减小,拉伸强度先增加后减小。随Z-pin植入间距和直径增加,X-cor夹层结构力学性能均增加。与泡沫夹层结构相比,X-cor夹层结构压缩、剪切和拉伸模量的测试值分别提高了1.26～5.15倍、2.50～13.56倍和1.90～2.71倍,压缩、剪切和拉伸测试值分别提高了1.63～9.20倍、1.28～2.03倍和1.01～2.30倍。     

X-cor夹层结构拉伸模量有限元分析

通过分析X-cor夹层结构中Z-pin端部的细观结构,提出Z-pin端部树脂区椭圆形态的基本假设并建立X-cor夹层结构拉伸模量的有限元模型,利用大型有限元软件ANSYS对其拉伸模量进行了数值计算。研究了Z-pin植入角度、直径和密度的改变对X-cor夹层结构拉伸模量的影响。结果表明:X-cor夹层结构的拉伸模量随Z-pin植入角度增加而减小,随Z-pin直径和密度增加而增加。通过有限元模型的计算,得到了X-cor夹层结构参数对其拉伸模量的影响规律,数值计算结果误差范围是±10%,验证了所提的有限元模型的合理性,说明该模型可用于预测其拉伸模量。     

X-cor夹层结构压缩模量有限元计算分析

通过分析X-cor夹层结构中Z-pin端部细观结构的显微镜照片,提出Z-pin端部树脂区椭圆形态的基本假设并建立X-cor夹层结构压缩模量的有限元模型,利用大型有限元软件ANSYS对其压缩模量进行数值计算,研究了Z-pin植入角度、直径和密度对X-cor夹层结构压缩模量的影响.结果表明,X-cor夹层结构的压缩模量随Z-pin植入角度的增加而减小,随Z-pin直径和密度的增加而增加.通过有限元计算,获得X-cor夹层结构参数对其压缩模量的影响规律,数值计算结果误差范围为士10％,验证所建立有限元模型的合理性,说明该模型可用于预测其压缩模量.     

夹层结构侧压性能试验方法(英文)

Seven sandwich construction properties test methods of the national standards(GB/T1452-1457,GB/T1464),which published in 2005 by People's Republic of China.Based on a large number of experiments and design,refer to international advanced national standards,with international advanced level,from the specimen size,experiment methods,laboratory fixtures,the calculate results are all more reasonable,scientific,comprehensive and practical than the international advanced country standards.This paper specifies the...     

玻璃纤维制备X-cor夹层结构工艺及压缩性能研究

研究了玻璃纤维制备复合材料夹层结构X-cor的工艺,探索了X-cor夹层结构压缩性能及植入角度、密度、Pin直径等因素对压缩性能的影响.同普通泡沫夹层结构相比,X-cor夹层结构的压缩强度提高9.7倍,压缩模量提高17.9倍.随着植入角的增加,单位体积分数的Pin对X-cor夹层结构的强度和模量的增强效率均提高;不同直径Pin对X-cor夹层结构影响不同,大直径Pin对X-cor夹层结构强度增强效率高;小直径Pin对X-cor夹层结构模量增强效率高.     

夹层梁弯曲试验分析

本文综合分析了夹层结构弯曲试验,提出了一种适用于高低温环境的试验方法,在常温条件下与国标试验方法GB1456进行了对比,并给出了NOMEX蜂窝夹层结构60℃、100℃和-55℃的部分试验结果,试验表明该方法可以较好地反映结构的弯剪特性。     

玻璃纤维制备X-cor夹层结构工艺及压缩性能研究EI

研究了玻璃纤维制备复合材料夹层结构X-cor的工艺,探索了X-cor夹层结构压缩性能及植入角度、密度、Pin直径等因素对压缩性能的影响.同普通泡沫夹层结构相比,X-cor夹层结构的压缩强度提高9.7倍,压缩模量提高17.9倍.随着植入角的增加,单位体积分数的Pin对X-cor夹层结构的强度和模量的增强效率均提高;不同直径Pin对X-cor夹层结构影响不同,大直径Pin对X-cor夹层结构强度增强效率高;小直径Pin对X-cor夹层结构模量增强效率高.     

A C1 finite element including transverse shear and torsion warping for rectangular sandwich beams

A new three‐noded C¹ beam finite element is derived for the analysis of sandwich beams. The formulation includes transverse shear and warping due to torsion. It also accounts for the interlaminar continuity conditions at the interfaces between the layers, and the boundary conditions at the upper and lower surfaces of the beam. The transverse shear deformation is represented by a cosine function of a higher order. This allows us to avoid using shear correction factors. A warping function obtained from a three‐dimensional elasticity solution is used in the present model. Since the field consistency approach is accounted for interpolating the transverse strain and torsional strain, an exact integration scheme is employed in evaluating the strain energy terms. Performance of the element is tested by comparing the present results with exact three‐dimensional solu‐tions available for laminates under bending, and the elasticity three‐dimensional solution deduced from the de Saint‐Venant solution including both torsion with warping and bending. In addition, three‐dimensional solid finite elements using 27 noded‐brick elements have been used to bring out a reference solution not available for sandwich structures having high shear modular ratio between skins and core. A detailed parametric study is carried out to show the effects of various parameters such as length‐to‐thickness ratio, shear modular ratio, boundary conditions, free (de Saint‐Venant) and constrained torsion. Copyright © 1999 John Wiley & Sons, Ltd.     

Low velocity impact analysis of composite sandwich shells using higher-order shear deformation theories

In the present investigation, higher-order and conventional first-order shear deformation theories are used to study the impact response of composite sandwich shells. The formulation is based on Donnell’s shallow shell theory. Nine-noded Lagrangian elements are used for the finite element formulation. A modified Hertzian contact law is used to calculate the contact force. The results obtained from the present investigation are found to compare well with those existing in the open literature. The numerical results are presented to study the changes in the impact response due to the increase of core depth from zero to some specified value and the changes in core stiffness for a particular core depth.     

复合材料夹层板屈曲强度的分散性分析

将面板单层及芯层厚度、 面板纤维方向角和材料参数作为随机变量, 通过编制基于高阶剪切理论的随机有限元程序, 对复合材料夹层板的屈曲强度分散性进行了分析, 得到了不同铺层方式下夹层板屈曲强度分散系数随纤维方向角及夹层板长厚比的变化规律。并通过对屈曲强度的分散系数进行灵敏度分析, 确定了影响分散系数大小的主要因素, 从而为材料设计、 制造工艺改进和夹层板结构可靠度的提高提供了理论依据。      

板式剪切型铅阻尼器的试验研究及有限元分析

提出一种新型的剪切型铅阻尼器,该装置中铅块直接嵌于滑动钢板与固定钢板的凹槽之间,构造简单。基于性能试验和有限元分析对该装置的滞回性能及关键参数进行了研究,研究结果表明:该阻尼器的滞回性能可以采用双线性模型加以模拟;阻尼器屈服阻尼力由铅块的剪切面积决定;加载曲线中弹性阶段与完全塑性阶段之间的过渡弧段的曲率半径与剪切铅块的长厚比成反比。     

Modal validation of sandwich shell finite elements based on a p‐order shear deformation theory including zigzag terms

This paper describes a set of improved C⁰‐compatible composite shell finite elements for evaluating the global dynamic response (natural frequencies and mode shapes) of sandwich structures. Combining a through‐the‐thickness displacement approximation of variable high order with a first‐order zigzag function, the proposed finite elements are suited for modelling sandwich plates and doubly curved shells with a non‐uniform thickness and are more accurate than conventional models based on the first‐ and third‐order shear deformation theories, especially in sandwich panels with highly heterogeneous properties. The new finite element model is then validated by a comparison with the standard shell and 3D solid models. From these investigations, it can be concluded that adding a zigzag function even to high‐order polynomial approximations of the through‐the‐thickness displacement is a useful tool for refining the modelling of sandwich structures. In addition, the proposed formulation is sufficiently versatile to represent with the same level of accuracy the behaviour of thin‐to‐thick laminated shells as well as of strongly heterogeneous sandwich structures. Copyright © 2008 John Wiley & Sons, Ltd.     

On using corrugated skins to carry shear in sandwich beams

A simplified approach is used to study the potential of using a corrugated skin in a sandwich to carry shear loads. Shear carrying capability is a major requirement for ship bottom panels, among other structures. The simplifications in the paper are quite major and in particular the corrugated skin is modeled as a conventional material with a homogenized stiffness. The goal of the paper is to point out some of the potentials as well as limitations of using a corrugated skin to carry shear loads. The major analysis tool was finite elements, although some analytical analyses were also performed. It was found that the introduction of a corrugated skin provided improved shear carrying capability and offered weight savings, particularly for heavily loaded sandwich beams. Alternative methods to increase shear strength were briefly reviewed.     

Time-dependent deformation of ROHACELL-core CFRP sandwich panels

In this study, we experimentally and analytically investigated time-dependent deformation of carbon-fiber reinforced plastic sandwich panels with three kinds of polymer foam-core ROHACELL, with the deformation caused by moisture absorption. Tensile tests for the ROHACELLs before and after moisture absorption were performed using the digital image correlation method, and we obtained a stress–strain relationship for each condition. Surface deformations of sandwich panels were calculated using finite element analyses to examine the elasto-plastic deformation of the ROHACELLs based on the tensile test results. Experimentally measured deformation in the sandwich panels varied depending on the cell size of cores, and the largest measured deformation after the moisture absorption was approximately 100 μm. This was much larger than the analytical result. On the basis of this study, we suggest that the main reason for the deformation may be an irreversible shrinkage of the ROHACELLs caused the absorption of moisture during exposure to high-temperature and high-humidity environments.     

Further developments in testing and analysis of the plate twist test for in-plane shear modulus measurements

The plate twist test for testing the in-plane shear modulus of composite materials is analysed. In the proposed test set-up the loads are not applied to the corners of the plate. This makes the test easier to perform than the original plate twist test. Based on a strength of materials approach, an analytical expression is found for the correction factor that accounts for the shifted position of the loading points. The analysis is made without making the assumption of equal bending stiffness in the diagonal directions of the plate, and can thus be applied for off-axis tests on orthotropic or lower symmetry composite materials.     

Constitutive model for quasi‐static deformation of metallic sandwich cores

All‐metal sandwich construction holds promise for significant improvements in stiffness, strength and blast resistance for built‐up plate structures. Analysis of the performance of sandwich plates under various loads, static and dynamic, requires modelling of face sheets and core with some fidelity. While it is possible to model full geometric details of the core for a few selected problems, this is unnecessary and unrealistic for larger complex structures under general loadings. In this paper, a continuum constitutive model is proposed as an alternative means of modelling the core. The constitutive model falls within the framework of a compressible rate‐independent, anisotropic elastic–plastic solid. The general form of the model is presented, along with algorithmic aspects of its implementation in a finite element code, and selected problems are solved which benchmark the code against existing codes for limiting cases and which illustrate features specific to compressible cores. Three core geometries (pyramidal truss, folded plate, and square honeycomb) are considered in some detail. The validity of the approach is established by comparing numerical finite element simulations using the model with those obtained by a full three‐dimensional meshing of the core geometry for each of the three types of cores for a clamped sandwich plate subject to uniform pressure load. Limitations of the model are also discussed. Copyright © 2004 John Wiley & Sons, Ltd.