Monotonic, multi-step and cyclic short beam shear tests were conducted on 2D and 3D woven composites. The test results were used to determine the effect of z-yarns on the inter-laminar shear strength as well as the multi-loading behavior. The presence of z-yarns was found to affect not only the inter-laminar shear strength of the composite but also the behavior of the composite beyond the elast...

Using high-resolution, in situ imaging of a hard, wedge-shaped model asperity sliding against a metal surface, we demonstrate a new mechanism for particle formation and delamination wear. Damage to the residual surface is caused by the occurrence of folds on the free surface of the prow-shaped region ahead of the wedge. This damage manifests itself as shallow crack-like features and surface tea...

The principal objectives of the research are to develop and experimentally validate a predictive modeling capability for simulation of wave propagation in 2-D composite plates. During this reporting period, the Wavelet Spectral Finite Element (WSFE) model for composite plates (developed by Prof. Gopalakrishnan at IISc Bangalore) was implemented at Clarkson. Composite plates were fabricated usin...

The dynamic delamination in woven glass ®ber reinforced plastic (GRP) composite is studied with a 3D ®nite deformation anisotropic viscoplastic model in conjunction with contact/cohesive laws. The large deformation of the material during impact loading is described through an anisotropic plasticity model in total Lagrangian co-ordinates whose coecients are determined experimentally. The intera...

We postulate that dominant damage modes in a fiber-reinforced laminated composite are fiber breakage, matrix cracking, fiber/ matrix debonding, and delamination/sliding. The first three damage modes are represented by internal variables with their development governed by constitutive relations. The delamination/sliding failure mode is presumed to initiate at a point on an interface between two ...

Electrical Resistance Tomography (ERT) offers a non-destructive evaluation (NDE) technique that takes advantage of the inherent electrical properties in carbon fiber reinforced polymer (CFRP) composites for internal damage characterization. This paper investigates a method of optimum selection of sensing configurations for delamination detection in thick cross-ply laminates using ERT. Reduction...

The influence of the delamination direction with respect to fiber orientation in adjacent plies on apparent interlaminar toughness is considered by proposing a general cohesive model. A local delamination-direction definition method adopted. Based mismatch between and direction, linear evolution developed. model implemented user-defined element subroutine ABAQUS validated case study single elem...

Reliable damage detection is one of the most critical tasks in composite plate structures. Ultrasonic guided waves are acknowledged as an effective way of structural health mo...

This study proposes an instantaneous damage localization technique for composite structures using noncontact laser ultrasonics. First, a velocity profile of the target composite structure is obtained by measuring wave velocities on paths with various directions. Second, laser ultrasonic responses from two excitation-sensing pairs, called inspection pairs, are obtained. Then possible damage loca...

A novel approach based on hidden Markov models (HMMs) is proposed for damage classification in composite structures. Time-frequency damage features are first extracted from the measured signals using the matching pursuit decomposition algorithm. The features are then incorporated as observation sequences to be modeled statistically by the HMMs. Once built, the HMMs are integrated very efficient...