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Fracture behavior of carbon fiber reinforced polymer composites: An optical study of loading rate effects
摘要： Crack initiation and growth in single-edge notched unidirectional T800s/3900-2 CFRP laminates are studied under stress wave and quasi-static loading conditions. An optical technique called reflection-mode Digital Gradient Sensing is also extended to study fracture mechanics of CFRP by using it in conjunction with ultrahigh-speed photography to perform full-field measurement of crack-tip deformations in the pre- and post-crack initiation regimes. DGS is capable of measuring two orthogonal surface slopes in the crack-tip vicinity as angular deflection of light rays. A method for extracting crack-tip parameters - the instantaneous crack speed and stress intensity factor (SIFs) histories - associated with the stationary and propagating cracks using measured surface slopes is presented. The effect of fiber orientation in the range 0°-60° relative to the initial notch and two loading rates are investigated. Nominally mode-I fracture occurs when the fiber orientation is 0° whereas mixed-mode fractures ensue in others. Besides crack initiation occurrence at higher loads as fiber orientation increases, the SIF histories imply strong fiber bridging at low fiber orientations under quasi-static conditions. Furthermore, this CFRP shows significant loading rate dependence during crack growth. Unlike stress wave loading conditions, an increasing crack growth resistance immediately after crack initiation is seen under quasi-static conditions.
关键词： Carbon fiber reinforced plastics,Loading rate effects,Crack growth behavior,Dynamic fracture,Digital Gradient Sensing
更新于2025-09-23 15:23:52
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Advanced Materials for Electromagnetic Shielding (Fundamentals, Properties, and Applications) || Mechanical Performance Characterization of EMI Shielding Materials Using Optical Experimental Techniques
摘要： In this chapter, the full field optical experimental methods for characterizing the mechanical performance of EMI shielding materials have been discussed. Interest in this type of physical problem is motivated by its importance in many practical applications. One major disadvantage of the use of optical techniques in characterizing the mechanical performance of EMI shielding materials is their full field and noncontact with the materials. The information outlined in this chapter may help researchers and engineers in their study of the unknown features of related complex systems for technological applications in characterizing EMI shielding materials.
关键词： EMI shielding materials,photoelastic method,digital gradient sensing,mechanical performance,moiré interferometry,digital image correlation,coherent gradient sensing,optical experimental techniques
更新于2025-09-04 15:30:14