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Carbon fiber-reinforced plastics (CFRP) laminate structures manufactured using prepregs usually contain fiber discontinuities that result from the prepreg cutting for design and cost-efficiency. In this study, the sampling moiré method was used to measure the microscopic strain of unidirectional CFRP laminates with fiber discontinuities to investigate the deformation behavior that causes damage. In addition to the strain distributions of the laminate before and after cracking, the strain results due to thermal residual stress relaxation and residual plastic deformation during cracking were also obtained. The experimental results of this study were in good agreement with the finite element method results. Our results revealed that the sampling moiré method is an accurate method of measuring microscopic strain that can be used to evaluate the mechanical properties, damage behavior, residual strains in laminates with fiber discontinuities, and other different materials and structures. [ABSTRACT FROM AUTHOR]

Phase-measuring profilometry is an accurate and effective technique for performing three-dimensional (3D) shape and deformation measurements of diffuse objects by fringe projection. However, phase analysis cannot be performed in underexposed or overexposed areas of the detector when an object with wide reflectance is measured. A novel intensity range extension method using a digital micromirror device (DMD) camera is proposed. In the optics of the DMD camera, each pixel of the CCD corresponds exactly to each mirror of the DMD. The phase-shifted fringe patterns with high contrast can be easily captured by programming an inverse intensity pattern that depends on the reflectance of the object. Our method can provide a wider intensity range and higher accuracy for 3D shape measurement than other conventional methods in both underexposed and overexposed areas. The measurements of a replica of a metallic art object and a flat plane are analyzed experimentally to verify the effectiveness of our method. In the experiment, the percentage of invalid points due to underexposure and overexposure can be reduced from 20% to 1%. OCIS codes: 100.2980, 110.6880, 120.2650, 120.4640, 120.5050.

A camera based on the digital micromirror device (DMD) technology has been previously developed. In this optical system, the correspondence of each mirror of the DMD to each pixel of the CCD cannot readily be done since the pixel sizes of the DMD and the CCD are very small. An accurate pixel-to-pixel correspondence adjustment in the DMD camera by means of the phase-shifting moire method is proposed. To perform high accurate adjustment of the optical system, the phase distribution of a moire fringe pattern is analyzed when the CCD pixels and the DMD mirrors have a mismatch and/or misalignment with each other. This technique does not need a complicated setting or complex image processing to generate the moire fringe pattern, and it needs only one captured image. In the adjustment experiment, the proposed method provided very accurate adjustment whose error was less than 1/25 pixel. An experiment of phase analysis to demonstrate the usefulness was performed. OCIS codes: 110.2970, 120.4120, 220.1140, 230.3990, 100.2650.

Out-of-plane displacement measurement is an important task not only to analyze the microelectronic device's behavior at the micro-scale but also to evaluate the structural health monitoring (SHM) of infrastructures at the meter-scale. In this study, an accurate and fast out-of-plane displacement measurement method with a single camera is presented, including the theoretical equations, and calibration of phase-gradient to out-of-plane displacement. Since the proposed method requires only a single grating image before and after deformation and analyzes by the sampling moiré method, it yields high accuracy and speed. An experiment of out-of-plane displacement with three different focal length lenses has been conducted to verify the validity of this method. Experimental results indicated that both small and large out-of-plane displacement measurements could be performed accurately. This optical measurement technique will be of high value for SHM of various infrastructures under digital camera or video/cinema camera recording. [ABSTRACT FROM AUTHOR]