Christian Heinrich¹, Anthony M. Waas²

CMC-Computers, Materials & Continua, Vol.35, No.2, pp. 155-181, 2013, DOI:10.3970/cmc.2013.035.155

Abstract The smeared crack approach (SCA) is revisited to describe post-peak softening in laminated composite materials. First, predictions of the SCA are compared against linear elastic fracture mechanics (LEFM) based predictions for the debonding of an adhesively bonded double cantilever beam. A sensitivity analysis is performed to establish the influence of element size and cohesive strength on the load-deflection response. The SCA is further validated by studying the in-plane fracture of a laminated composite in a single edge bend test configuration. In doing so, issues related to mesh size and their effects (or non-effects) are discussed and compared against other predictive… More >

Jennifer D. Rhymer¹, Hyonny Kim¹

CMC-Computers, Materials & Continua, Vol.35, No.2, pp. 87-117, 2013, DOI:10.3970/cmc.2013.035.087

Abstract Polymer matrix composite structures are exposed to a variety of impact threats including hail ice. Internal delamination damage created by these impacts can exist in a form that is visually undetectable. This paper establishes an analysis methodology for predicting the onset of delamination damage in toughened carbon/epoxy composite laminates when impacted by high velocity ice spheres (hailstones). Experiments and analytical work focused on ice sphere impact onto composite panels have determined the failure threshold energy as a function of varying ice diameter and panel thickness, and have established the ability to predict the onset of delamination using cohesive elements in… More >

A. T. Rhead¹, T. J. Dodwell¹, R. Butler^1,2

CMC-Computers, Materials & Continua, Vol.35, No.1, pp. 1-16, 2013, DOI:10.3970/cmc.2013.035.001

Abstract When (robotic) Automated Fibre Placement (AFP) is used to manufacture aerospace components with complex three dimensional geometries, gaps between fibre tows can occur. This paper explores the interaction under compressive load of these tow gaps with impact damage. Two coupons with different distributions of tow-gaps were impacted. Results indicated that the area of delamination is smaller for an impact directly over a tow gap where the tow gap is situated close to the non-impact face. Subsequent Compression After Impact (CAI) testing demonstrated that both the formation of sublaminate buckles and subsequent growth of delaminations is inhibited by the presence of… More >

Jia-Liang Le¹, Bing Xue¹

CMC-Computers, Materials & Continua, Vol.34, No.3, pp. 251-264, 2013, DOI:10.3970/cmc.2013.034.251

Abstract It has been recently shown that the nominal structural strength of metal-composite structures depends on the structure size, and such dependence is strongly influenced by the stress singularities. Nevertheless, previous studies only focused on structures that exhibit very strong stress singularities, which are close to the crack-like stress singularity. In the actual engineering designs, due to the mismatch of material properties and complex structural geometries, many metalcomposite structures may contain stress singularities that are much weaker than the crack-like stress singularity. This paper presents a numerical study on the size dependence of scaling of fracture of metal-composite hybrid structures for… More >

Chandra Veer Singh^1,*

CMC-Computers, Materials & Continua, Vol.34, No.3, pp. 227-249, 2013, DOI:10.3970/cmc.2013.034.227

Abstract A non-linear damage model is developed for the prediction of stiffness degradation in composite laminates due to transverse matrix cracking. The model follows the framework of a recently developed synergistic damage mechanics (SDM) approach which combines the strengths of micro-damage mechanics and continuum damage mechanics (CDM) through the so-called constraint parameters. A common limitation of the current CDM and SDM models has been the tendency to over-predict stiffness changes at high crack densities due to linearity inherent in their stiffness-damage relationships. The present paper extends this SDM approach by including higher order damage terms in the characterization of ply cracking… More >

A. Ataş¹, C. Soutis²

CMC-Computers, Materials & Continua, Vol.34, No.3, pp. 199-226, 2013, DOI:10.3970/cmc.2013.034.199

Abstract A strength prediction method is presented for double-lap single fastener bolted joints of cross-ply carbon fibre reinforced plastic (CFRP) composite laminates using cohesive zone elements (CZEs). Three-dimensional finite element models were developed and CZEs were inserted into subcritical damage planes identified from X-ray radiographs. The method makes a compromise between the experimental correlation factors (dependant on lay-up, stacking sequence and joint geometry) and three material properties (fracture energy, interlaminar strength and nonlinear shear stress-strain response). Strength of the joints was determined from the predicted load-displacement curves considering sub-laminate and plylevel scaling effects. The predictions are in a reasonable agreement with… More >

Shiv Narayan¹, Latha S.¹, R M Jha¹

CMC-Computers, Materials & Continua, Vol.34, No.2, pp. 131-142, 2013, DOI:10.3970/cmc.2013.034.131

Abstract The EM performance analysis of a multilayered metamaterial based radar absorbing structure (RAS) has been presented in this paper based on transmission line transfer matrix (TLTM) method for millimeter wave applications. The proposed metamaterial-RAS consists of cascaded DPS and MNG layers of identical configurations. It exhibits extremely low reflection (< 42 dB) at 95 GHz and absorbs more than 95% power of incident wave over the frequency range of 90.4- 100 GHz without metal backing for both TE and TM polarizations. In view of aerospace applications, the reflection, transmission, and absorption characteristics of the proposed metamaterial-RAS are also studied at… More >

Jiaojiao Du¹, Guojian Li¹, Qiang Wang^1,2, Yongze Cao¹, Jicheng He¹, Yonghui Ma¹

CMC-Computers, Materials & Continua, Vol.34, No.2, pp. 117-129, 2013, DOI:10.3970/cmc.2013.034.117

Abstract The effects of high magnetic field and post-annealing on the structural, electrical and magnetic properties of the evaporated Ni films were investigated and compared. The in-situ application of a 6 T magnetic field during evaporation or post-annealing at 200°C did not change the crystal structures of the films. However, the magnetic field makes the films exhibit the smallest grain size and the lowest surface roughness. Crystallinity was improved for both the 6 T films and the annealed films. This leads to the enhancement of saturation magnetization (Ms). The value of Ms for the 0 T films was 588 emu/cm3, while… More >

Bingfei Liu¹, Guansuo Dui^2,3, Benming Xie¹, Libiao Xin³, Lijun Xue³

CMC-Computers, Materials & Continua, Vol.34, No.1, pp. 83-94, 2013, DOI:10.3970/cmc.2013.034.083

Abstract Functionally Graded Materials (FGMs) are being used in an everexpanding set of applications. For better applications, an analytical methodology using averaging technique of composites is developed to describe the thermo-elastic and thermo-elastoplastic behaviors of a three-layered FGM system subjected to thermal loading Solutions using averaging technique of composites for the stress distributions in a generic FGM system subjected to arbitrary temperature loading conditions are presented. The power-law strain hardening behaviour is assumed for the FGM metallic phase and the stress of the metallic phase are calculated to judge the plastic in this work The stress distributions within the FGM systems… More >

F. Wang^1,2, D.M. Zhang^1,2,3, H.H. Zhu⁴, H.W. Huang^1,2, J.H. Yin⁵

CMC-Computers, Materials & Continua, Vol.34, No.1, pp. 63-81, 2013, DOI:10.3970/cmc.2013.034.063

Abstract This paper studies the impact of overhead excavation on an existing tunnel through both field monitoring and a full 3D numerical model. It is found that the excavation induced longitudinal heave of the tunnel is uneven with maximum heave occurring below the excavation center. Even at the same cross section, the excavation induced heave is not uniform with the most significant heave occurring at the tunnel crown. The bending moments of the tunnel lining is decreased due to the overhead excavation. The axial forces of the tunnel lining generally decrease except at the tunnel invert. The shear forces of the… More >