Abstract
The failure and residual strength after low-velocity impact of stitched composites are very important in their service and maintenance phases. In order to capture the failure and residual strength more accurately, a full-process numerical analyzing method was developed in this paper. The full-process numerical analyzing method includes two parts: (1) Part 1 is the progressive low-velocity impact damage prediction method for stitched composites; (2) Part 2 is the progressive residual strength prediction method by introducing all types of damage that are caused by the low-velocity impact as the analysis presuppositions. Subsequently, the failure and residual strength of G0827/QY9512 stitched composites were simulated by the full-process numerical analyzing method. When compared with experiments, it is found that: (1) the maximum error of low-velocity impact damage areas was 17.8%, and their damage modes were similar; (2) the maximum error of residual strength was 8.9%. At last, the influence rules of stitched density and stitching thread thickness were analyzed. The simulation results showed that, if there is no suture breakage failure, stitched density affects the mechanical properties of the stitched composites, while stitching thread thickness has little effect on it; otherwise, both factors have a significant effect on the mechanical properties.
Highlights
Stitched composites, which can be fabricated by inserting high-strength threads in through thickness direction into the preforms prior to resin consolidation process, have been widely used in various engineering fields, especially in aerospace, marine, motor sport, military, and specialist construction, due to their excellent impact resistance and compression-after impact strength [1]
According to the References [21,25,27], the material property degradation rules with regard to different failure modes during the impact numerical analysis process are assumed, as follows: (1) Fiber tension failure: all the material parameters are reduced to 0.07 of the original; (2) Fiber compression failure: all the material parameters are reduced to 0.14 of the original; (3) Matrix tension failure: E2, G12, G13 are reduced to 0.2 of the original; (4) Matrix compression failure: E2, G12, G13 are reduced to 0.4 of the original; (5) Delamination failure: E3, G12, G13, ν12, ν13 are reduced to 0.01 of the original; and, (6) Suture breakage failure: The stiffness of the stitches degenerates to 100 Pa
According to the Reference [29], the material property degradation rules with regard to different failure modes during the residual strength numerical analysis process are assumed, as follows: (1) Fiber tension failure: all the material parameters are reduced to 0.002 of the original; (2) Fiber compression failure: all the material parameters are reduced to 0.002 of the original; (3) Matrix tension failure: E2 is reduced to 0.2 of the original; (4) Matrix compression failure: E2 is reduced to 0.008 of the original; (5) Delamination failure: E3, G12, G13, ν12, ν13 are reduced to 0; and, (6) Suture breakage failure: The stiffness of the stitches degenerates to 100 Pa
Summary
Stitched composites, which can be fabricated by inserting high-strength threads in through thickness direction into the preforms prior to resin consolidation process, have been widely used in various engineering fields, especially in aerospace, marine, motor sport, military, and specialist construction, due to their excellent impact resistance and compression-after impact strength [1]. There is a great deal of studies that are related to the mechanical properties of stitched composites, which are fundamentally important in design phases. Heß proposed a finite element based unit cell model to simulate the in-plane and out-of-plane properties of the stitched composite laminates [2,3]. Sci. 2018, 8, 2698 plain experimentally studied [4]. Yudhanto experimentally studied the damage mechanisms of the stitched composites, which include tensile and compressive properties [1,5,6]. Vallons investigated the influence of the stitching pattern on the mechanical properties of glass fiber non-crimp fabric composites [7]
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