TENSILE IMPACT DELAMINATION OF A CROSS-PLY INTERFACE STUDIED BY MOIRÉ PHOTOGRAPHY

• Published in: Fatigue & fracture of engineering materials & structures 1995-10, Vol.18 (10), p.1101-1114
• Main Authors: Melin, L. G., Thesken, J. C., Nilson, S., Benckert, L. R.
• Format: Article
• Language: English
• Subjects: Applied sciences; Exact sciences and technology; Experimental Mechanics; Experimentell mekanik; Forms of application and semi-finished materials; Laminates; Polymer industry, paints, wood; Technology of polymers
• ISSN: 8756-758X; 1460-2695; 1460-2695
• DOI: 10.1111/j.1460-2695.1995.tb00842.x

Impact induced delamination along a cross‐ply interface in carbon fiber/epoxy laminates is studied by high resolution moiré photography. The specimens were loaded in a tensile split‐Hopkinson bar giving mode I dominated fracture, and a high speed camera captures images during loading and delamination. The resulting moiré fringes are analysed to produce full field displacement maps of the area around the loaded and propagating crack tips. The displacement map prior to failure shows good agreement with numerical solutions, calculated using a 3D self‐adaptive p‐version of the finite element method. The calibrated finite element solutions are then used to give further information about the matrix cracking zone size around the crack tip and the energy release rate. In comparison to quasi‐static loading, tensile impact loading was found to increase the failure load and the resulting energy release rates; some physical explanations for this behaviour are discussed. It was concluded that the procedures presented have good potential for further determination of rate dependent material properties in carbon/fiber epoxy composites.