Single yarn pull-out test is a model experiment method to research the mechanical properties of fabric under impact. This study aims to understand the yarn pull-out mechanism and fabric shear deformation behavior of Kevlar 49 plain fabric by using the single yarn pull-out test combined with the digital image correlation method. The load-displacement curve contains typical physical phenomena such as crimp extension, crimp swap, frictional slip of yarn, and fabric deformation behavior. In the static friction stage, the pull-out load increased nonlinearly with the displacement, and the crimp extension of the pulled warp yarn occurred gradually. In the kinetic friction stage, the load decreased undulately until the warp was pulled out. Moreover, the fabric shear deformation sharply increased in the static friction stage, then decreased slowly during the kinetic friction stage. It was found that fabric shear deformation was still apparent after the yarn was completely pulled out.

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Recent advances of interfacial micromechanics in fiber reinforced composites using micro-Raman spectroscopy are given. The faced mechanical problems for interface design in fibrous composites are elaborated from three optimization ways: material, interface, and computation. Some reasons are depicted that the interfacial evaluation methods are difficult to guarantee the integrity, repeatability, and consistency. Micro-Raman study on the fiber interface failure behavior and the main interface mechanical problems in fibrous composites are summarized, including interfacial stress transfer, strength criterion of interface debonding and failure, fiber bridging, frictional slip, slip transition, and friction reloading. The theoretical models of above interface mechanical problems are given.

The full-field stress distribution of a two-dimensional plain fabric was mapped using micro Raman spectroscopy (MRS) through a novel yarn push-out test, simulating a quasi-static projectile impact on the fabric. The stress-strain relationship for a single yarn was established using a digital image correlation method in a single-yarn tensile test. The relationship between Raman peak shift and aramid Kevlar 49 yarn stress was established using MRS in a single-yarn tensile test. An out-of-plane loading test was conducted on an aramid Kevlar 49 plain fabric, and the yarn stress was measured using MRS. From the full-field fabric stress distribution, it can be observed that there is a cross-shaped distribution of high yarn stress; this result would be helpful in further studies on load transfer on a fabric during a projectile impact.