Microcracking in composite laminates: Simulation of crack-induced ultrasound attenuation

Self Cite

A computational study is performed to determine the contribution to ultrasound attenuation in carbon fiber reinforced polymer composite laminates of linear elastic scattering by matrix micro-cracking. Multiple scattering approximations are benchmarked against exact computational approaches. Results support linear scattering as the source of observed increased attenuation in the presence of micro-cracking. Center for NDE, Iowa State University, Ames, IA 50014 2 NASA Langley, Hampton, VA 23681 ABSTRACT. A computational study is performed to determine the contribution to ultrasound attenuation in carbon fiber reinforced polymer composite laminates of linear elastic scattering by matrix micro-cracking. Multiple scattering approximations are benchmarked against exact computational approaches. Results support linear scattering as the source of observed increased attenuation in the presence of micro-cracking.

“…A detailed discussion of EFIT application to eq. (1) is found in [3] within these proceedings. Work at CNDE reformulates eq.…”

Section: Numerical Methods and Proceduresmentioning

confidence: 92%

Computational modeling of micro-crack induced attenuation in CFRP composites

Roberts¹,

Leckey²

2013

Self Cite

“…Matrix micro-cracking is considered a precursor to a more advanced damage state, hence a means to quantitatively assess levels of microcracking would serve early damage detection. Experiments as reported in [1,2] indicate that an increase in ultrasound attenuation accompanies micro-cracking. The present work seeks to determine if the observed attenuation is attributable to linear elastic wave scattering, as opposed to, say, increased non-linear frictional losses.…”

Section: Introductionmentioning

confidence: 98%

“…As such, mechanical properties are specified by mass density U and five independent elastic constants, with stress W ij and displacements u i related via the constitutive relation W ij =c ijkl u k,l . Wave motion within the laminate is governed by the elastodynamic field equation, expressed for assumed time harmonic motion with frequency Z and applied body forces f i (x) as (1) with continuity of displacements and tractions at the ply interfaces imposed as boundary conditions. [3] Laminate matrix micro-cracking introduces the additional boundary condition of zero traction over crack surfaces.…”

Section: Model Formulationmentioning

confidence: 99%

Micro-crack ultrasound scattering in anisotropic composite laminates

Roberts¹

2013

A computational model of ultrasound scattering by micro-cracks in fiber reinforced polymer laminates is presented, foundational to study of micro-crack induced ultrasound attenuation. A model for transmission scattering response is developed using a boundary integral formulation, and associated approximate scattering theories are discussed. Numerical results are presented demonstrating application of the model to laminates containing distributed micro-cracking. ABSTRACT. A computational model of ultrasound scattering by micro-cracks in fiber reinforced polymer laminates is presented, foundational to study of micro-crack induced ultrasound attenuation. A model for transmission scattering response is developed using a boundary integral formulation, and associated approximate scattering theories are discussed. Numerical results are presented demonstrating application of the model to laminates containing distributed micro-cracking. Keywords

“…Details about its implementation in composite materials may be found in a companion article in these Proceedings [3]. The model volume is first discretized in both space and time, with volume elements being small compared to the sonic wavelength.…”

Section: Model Approaches and Comparisonsmentioning

confidence: 99%

“…In this paper we explore the use of one such approximate model based on earlier work by Minachi et al [2], denoted here as the "simple" model. Its practical accuracy is gauged by comparisons to more exact model calculations using the elastodynamic finite integration technique (EFIT) [3]. We begin by describing several composite specimens that were fabricated to contain real or artificial delaminations.…”

Section: Introductionmentioning

confidence: 99%

Modeling the effects of beam size and flaw morphology on ultrasonic pulse/echo sizing of delaminations in carbon composites

Margetan¹,

Leckey²,

Barnard³

2013

The size and shape of a delamination in a multi-layered structure can be estimated in various ways from an ultrasonic pulse/echo image. For example the −6dB contours of measured response provide one simple estimate of the boundary. More sophisticated approaches can be imagined where one adjusts the proposed boundary to bring measured and predicted UT images into optimal agreement. Such approaches require suitable models of the inspection process. In this paper we explore issues pertaining to model-based size estimation for delaminations in carbon fiber reinforced laminates. In particular we consider the influence on sizing when the delamination is non-planar or partially transmitting in certain regions. Two models for predicting broadband sonic time-domain responses are considered: (1) a fast "simple" model using paraxial beam expansions and Kirchhoff and phase-screen approximations; and (2) the more exact (but computationally intensive) 3D elastodynamic finite integration technique (EFIT). Model-to-model and model-to experiment comparisons are made for delaminations in uniaxial composite plates, and the simple model is then used to critique the −6dB rule for delamination sizing. ABSTRACT. The size and shape of a delamination in a multi-layered structure can be estimated in various ways from an ultrasonic pulse/echo image. For example the -6dB contours of measured response provide one simple estimate of the boundary. More sophisticated approaches can be imagined where one adjusts the proposed boundary to bring measured and predicted UT images into optimal agreement. Such approaches require suitable models of the inspection process. In this paper we explore issues pertaining to model-based size estimation for delaminations in carbon fiber reinforced laminates. In particular we consider the influence on sizing when the delamination is non-planar or partially transmitting in certain regions. Two models for predicting broadband sonic time-domain responses are considered: (1) a fast "simple" model using paraxial beam expansions and Kirchhoff and phase-screen approximations; and (2) the more exact (but computationally intensive) 3D elastodynamic finite integration technique (EFIT). Model-to-model and model-to experiment comparisons are made for delaminations in uniaxial composite plates, and the simple model is then used to critique the -6dB rule for delamination sizing.