[en] This study designed a novel porous acoustic-absorbing composite laminates structure with reinforced mechanical properties. Three-dimensional crimped hollow polyester (3D CHPET) fiber and high resilience polyester (HRPET) fibers with various blending ratio were fabricated into porous base fabric. Kevlar woven plain fabric was embedded between HRPET/CHPET porous base fabrics to reinforce strength, which were combined through needle punching and thermal bonding process. Air permeability and tear strength of the acoustic-absorbing composite laminates were tested to evaluate the mechanical properties of the acoustic-absorbing composite laminates. The results showed that the acoustic-absorbing composite laminates exhibited a little higher air permeability after being thermal-treated. Tear strength of the thermal-treated composite laminates was also better than that without thermal treating. (paper)

[en] A direct phase shift extraction and wavefront reconstruction method in two-step generalized phase-shifting interferometry (GPSI) with arbitrary unknown phase shift is proposed. In this method the unknown phase shift α can be extracted by a determinate formula directly without iteration or additional judgment of its correct value from two or more phase shift solutions as necessary before. By an appropriate formula of GPSI the complex object field in the recording plane can be calculated and then the object wavefront in the original object plane obtained. This method is applicable for GPSI of any frame number K≥2 and for both the amplitude and phase objects. Computer simulations have shown that the phase shift extraction errors are below 0.01 rad in a wide range of 0.4 rad<α<2.6 rad and the computation time is greatly reduced by a factor of about 20 compared with the previous method. The effectiveness and accuracy of this method are also verified by optical experiments