The local cyclic plasticity of the interface around a broken fiber in ductile matrix composites under the in-phase and out-of-phase thermomechanical fatigue (TMF) loads is analyzed by using the single-fiber shear-lag model. The elastic, perfectly-plastic shear stress-strain relation is used to model the thermomechanical behavior of the fiber/matrix interface. It is shown that the alternating plastic shearing of the interface takes place under an appropriate combination of mechanical stress and thermal load. In the stress versus temperature diagram the so-called cyclic plasticity zone is identified. A new parameter, i.e. the cyclic plasticity length, L s, is found which is smaller than the yield length, Ls, caused by monotonic loading. The closed-form solutions for L s, Ls, the fiber stress profiles and the cyclic plastic shear strain range, p, are obtained. L s and p increase for both the in-phase and out-of-phase TMF conditions as the mechanical load and/or thermal load increase. The in-phase condition produces a higher plastic shear strain range than the out-of-phase condition does. The solutions obtained may be used for modeling fiber/matrix debonding caused by the fiber breakage under TMF fatigue loading.

This two-part contribution presents a novel and efficient method to analyze the two-dimensional (2-D) electromechanical fields of a piezoelectric layer bonded to an elastic substrate, which takes into account the fully coupled electric and mechanical behaviors. In Part I, we have obtained a system of governing integro-differential equations for the structure via a variational principle. This part presents a numerical solution algorithm of the integro-differential equations and the numerical results of some applications. A numerical algorithm for solving the system of four integrodi erential equations with strongly singular kernels is developed. The convergence of the numerical algorithm is discussed. The numerical results suggest that the fully coupled electromechanical analysis is helpful for a better understanding of the performance of the piezoelectric sensor and actuator. The interfacial normal stress is much higher than the interfacial shear stress, suggesting that the interfacial normal stress causes a delamination initiation.

The elastic properties of symmetric laminates containing a cracked mid-layer are predicted by using the equivalent constraint model (ECM) proposed recently by the authors. In accordance with the ECM methodology the symmetric laminates subjected to an in-plane tension/shear load are subdivided into such sublaminates as the cracked centrallayer, two nearest laminae and two homogeneous layers smeared from the remaining plies (if applicable). The

Transverse ply cracking and its induced delaminations at the ø/90 interfaces in […/:øi/øm/90n]s laminates are theoretically investigated. Three cracked and delaminated model laminates, one five-layer model (FLM) laminate [SL/øm/902n/øm/SR]: and two three-layer model (TLM) laminates I and II, [øm//902n/øm/] and [SL/902n SR] are designed to examine constraining mechanisms of the constraining plies of the center 90-ply group on transverse crack induced delaminations, where SL\SL, SR, SL and SR are sublaminates [.../C] [øi…] […/øi/øm] and [øm/øi/…] respectively, A sublaminate!wise _rst!order shear laminate theory is used to analyze stress and strain elds in the three cracked and delaminated laminates loaded in tension [The extension sti] ness reduction of the constrained 89-plies and the strain energy release rate for a local delamination normalized by the square of the laminate strain are calculated as a function of delamination length and transverse crack spacing[ The constraining e]ects of the immediate neighboring plies and the remote plies are identi_ed by conducting comparisons between the three model laminates[It is seen for the examined laminates that the nearest neighboring ply group of the 89-plies primarily a]ects the sti]ness reduction and also the normalized strain energy release rate\whereas the in uences of the remote constraining layers are negligible