1. Hyperspectral Scanning Data collection and live-display surfaces.
Progressive failure analysis of hyperspectrally detected waviness in plain weave carbon/epoxy composite laminate
Seyedmohammad Shams, PhD candidate & Dr. Rani Elhajjar, Associate Professor- Civil Engineering and Mechanics Department
Introduction
Composite structures in practice can be subjected to wrinkling defect originating to manufacturing process. The visibly superficially resin rich area can produce waviness typically impacting all or some of the plies in a laminate stack. The damage behavior of laminated composites based on initiation and growth of damage under random through the thickness waviness is investigated to evaluate the performance of the defected laminate under flexural loading.
Fiber waviness profile in a composite
wind turbine blade
Hyperspectral Scanning
The out of plane waviness have been detected by the non-destructively spot checking hyperspecteral imaging system. Near Infrared (NIR) imaging can accurately measure surface resin on composite materials from 2 to 75 mils thick, detecting virtually all resin pockets, resin filled surface wrinkles and other surface resin features.
Data collection and live-display surfaces.
This image shows a series of surface resin pockets in the NIR image and a visible resin feature on the surface in the video image
Diagram of the hyperspectral camera scanning over the exterior of a wing part

2. Specimen models using computer aided design process
Progressive failure analysis of hyperspectrally detected waviness in plain weave carbon/epoxy composite laminate
Seyedmohammad Shams, PhD candidate & Dr. Rani Elhajjar, Associate Professor- Civil Engineering and Mechanics Department
Experiments
Plain Weave aerospace grade Fabric prepreg system has been targeted to investigate the effect of ply waviness on the structural strength. A number of 11 plies of 0/90 fabric is cured with hot press based on manufacturer suggested process. The wrinkles are produced by using additional pressure emerged from the mold. The 3- point flexural test has been performed according to ASTM D760.
Failure progression of specimens
with different fiber waviness amplitude
3point flexural test setup
Modeling Process
The STL file format is used to create a surface of the random waviness from hyperspectral imaging using MATCAD software. The STL is a file format native to the stereolithography CAD software created by 3D systems. Three specimens have been cut from the highest fiber waviness zone of the main panel where the waviness pattern on each specimen is unique.
Specimen models using computer aided design process
Resin Pocket
Area of fiber waviness

3. Progressive Failure Analysis
Progressive failure analysis of hyperspectrally detected waviness in plain weave carbon/epoxy composite laminate
Seyedmohammad Shams, PhD candidate & Dr. Rani Elhajjar, Associate Professor- Civil Engineering and Mechanics Department
Progressive Failure Analysis
The progressive failure methodology is used to characterize damage mechanisms of through thickness fiber waviness on the flexural strength of the continuous in-plain weave fabric carbon laminate. A finite element modeling framework is proposed for the in-plain weave composite laminates comprising adjusted Hashin-puck’s continuum damage criteria and cohesive layers model.
Load-displacement of wavy samples
Fiber fracture and delamination at final failure
Results
Experimental and numerical results have shown the waviness can significantly impact the flexural strength of the laminates derived by spreading the interlaminar failure on defected areas. The failure mechanisms consist of interlaminar failure at the area of fiber waviness/resin pocket and fiber/matrix failure at final load capacity.
Interlaminar failure predicted by CZM
Acknowledgments
1- Gabor J. Kemeny, Gard A. Groth, Gina Stuessy, Chris Zueger, Middleton Research University Green, Middleton WI 53562
2- Ahmad Pahlavan Tafti, Computer Science Department, University of Wisconsin Milwaukee