Residual Strength of Stitched Laminates After Low Velocity Impact

Abstract

Tests were conducted with stitched laminates in order to calculate CAI (compression after impact) strength and TAI (tension after impact) strength for stitched laminates. Two levels of low velocity impact energy were used. All the specimens were made of two different types of lay-up sequence laminates with three different stitching directions of 08, 458, and 908. FEM model was developed using MSC/PATRAN software to predict the CAI and TAI strength of stitched laminates. PS criterion (point stress) and FD criterion (fiber breakage in damage zone) were applied to predict CAI strength. It showed that the predicted residual strengths were in agreement with the test results. Stitching improves the residual strength of the laminates.

Morphological study of damage evolution in woven-laminates subjected to high-velocity impact

“…Delamination is a critical failure mechanism since it causes big losses of the structure's residual compressive strength after impact [9][10][11][12]. Most of the time, the largest axis of delamination damage runs in the direction of the fibres of the lower sheet [3].…”

“…Most of the time, the largest axis of delamination damage runs in the direction of the fibres of the lower sheet [3]. After perforation, it has been shown that the residual tensile strength of woven laminates diminishes [10].…”

“…The first step to evaluate the residual properties of composite laminates subjected to impact is to study the damaged area, its location and morphology [9][10][11][12].…”

Comparison of off-axis angle on the low velocity impact behaviors for carbon-fiber-reinforced polymer laminates

“…Compared to composite CAI strength studies, less research has been performed regarding tension after impact (TAI) strength, also a very important issue in evaluation and design of composite structures. Cheng et al 21 used both numerical and experimental methods in studying TAI strength of stitched laminates. Two different types of laminate lay-up sequences with three different stitching directions of 0 o , 45 o , and 90 o were considered, with two levels of low-velocity impact energy applied to the specimens.…”

A Pre-Stitching Method to Manufacture Z-Pins Reinforced Woven Ceramic Matrix Composite Laminates

“…Compared with 3D braided ceramic matrix composite (CMC), 2D woven CMC laminate has the advantages of lower manufacture cost and better stiffness design and the disadvantages of weaker interlaminar strength and easier delamination. Scholars began an investigation into improving interlaminar fracture toughness of composite materials and put forward many different interlayer toughening methods, such as, interleaved film toughening [1,2] , thermoplastic-particle interlayer toughening [3,4] , stitching [5][6][7] and Z-pins [8][9][10][11][12] . Interleaved film and thermoplastic-particle interlayer toughening methods are feasible for the polymer composites, but can not be used in ceramic matrix composites.…”