“…However, due to the existence of delaminations, Specimen B goes through I, II and III stages corresponding to the instability failure of daughterboard of ①, ② and ③ respectively. The ultimate strength of Specimen B is much less than that of Specimen A, indicating the degradation of carrying capacity of composite can be extremely influenced by the existence of delaminations, which is confirmed by Kazemianfar et al [18]. According to the comparison of the two mechanical curves, the slope of Specimen A is higher than the overall slope of Specimen B.…”
Section: Effects Of Delaminations On Damage Evolution Of Specimenssupporting
The study on natural aging of fiber reinforced composite, delamination damage behavior and damage pattern recognition plays a significant role in structural health monitoring of the material. In this study, acoustic emission is used to investigate damage evolution process and damage mechanisms in unidirectional glass and carbon-glass orthogonal woven fiber reinforced composites containing symmetric multiple delaminations under three point bending testing. Based on the principle of control variables, four kinds of specimens are manufactured to investigate the comparative study for the effects of delaminations, reinforced materials and fiber orientation on buckling failure behaviors and the effects of aging on mechanical properties. The results indicate that the degradation of strength and stiffness of composite can be influenced by the existence of delamination defects and natural aging condition. Both negative and positive effects can be generated by natural aging condition. Moreover, reinforced materials, porosity and fiber orientation are important factors influencing the reliability of composite. Clustering results of unidirectional fiber reinforced composites indicate interphase failure is the main damage component, moreover, the existence of symmetrical multiple delaminations will aggravate the damage of composite and make instability failure characterized by intermittency.
“…However, due to the existence of delaminations, Specimen B goes through I, II and III stages corresponding to the instability failure of daughterboard of ①, ② and ③ respectively. The ultimate strength of Specimen B is much less than that of Specimen A, indicating the degradation of carrying capacity of composite can be extremely influenced by the existence of delaminations, which is confirmed by Kazemianfar et al [18]. According to the comparison of the two mechanical curves, the slope of Specimen A is higher than the overall slope of Specimen B.…”
Section: Effects Of Delaminations On Damage Evolution Of Specimenssupporting
The study on natural aging of fiber reinforced composite, delamination damage behavior and damage pattern recognition plays a significant role in structural health monitoring of the material. In this study, acoustic emission is used to investigate damage evolution process and damage mechanisms in unidirectional glass and carbon-glass orthogonal woven fiber reinforced composites containing symmetric multiple delaminations under three point bending testing. Based on the principle of control variables, four kinds of specimens are manufactured to investigate the comparative study for the effects of delaminations, reinforced materials and fiber orientation on buckling failure behaviors and the effects of aging on mechanical properties. The results indicate that the degradation of strength and stiffness of composite can be influenced by the existence of delamination defects and natural aging condition. Both negative and positive effects can be generated by natural aging condition. Moreover, reinforced materials, porosity and fiber orientation are important factors influencing the reliability of composite. Clustering results of unidirectional fiber reinforced composites indicate interphase failure is the main damage component, moreover, the existence of symmetrical multiple delaminations will aggravate the damage of composite and make instability failure characterized by intermittency.
“…The stereo microscope images are similar to the studies in the literature. 57,58 Figure 12.Stereo microscope images of front face and rear face images of the composites as samples (a) A1, (b) A2, (c) B1, (d) B2, (e) C1, (f) C2, (g) D1, and (h) D2. These stereo microscope images were taken after the impact tests.Figure 13.The stereo microscope images of the surfaces of A1 and A2 composites after impact tests (a) front of A1, (b) backward of A1, (c) front of A2, and (d) backward of A2 composite.…”
Recently, glass fiber reinforced polymer composites have been increasingly used in applications which are exposed to impact loads due to their high strength, low weight, and corrosion resistance properties. Therefore, the effect of curvature of composite laminate on their impact resistance is important. In this study, the mechanical properties of three curvature diameters and two stacking sequences, which have not been compared before, were examined and compared. The diameter of curved composites is 760 mm, 380 mm, and 304 mm and flat designated as A, B, C, and D, respectively. The fiber stacking orders are [0/0/-45/+45/90/90]S and [90/90/-45/+45/0/0]S designated as Type 1 and Type 2, respectively. The drop-weight impact tests were performed and failure modes of composites were examined. It was observed that the impact resistance decreases with the increase of curvature, where 760 mm diameter and Type 2 composites had the highest strength in all of the composites. In addition, delamination, fiber breakage, and matrix cracking failure modes were observed in the composites after impact. The reason why the strength decreases as the curvature of the composite increases is that the curved areas create an effect that increases the external force applied. The reason why Type 2 stacking order is more durable than Type 1 stacking order is that the 90° fiber direction in the bottom layer has a damping effect on the applied force. According to the results of this study, composite materials with larger diameter and stacking order starting with 0° provides more mechanical strength. [Formula: see text]
“…In the case of the 3D woven architectures, despite the comparable energy absorption of both the ORT-PW and ORT-TW, the damage is less severe in the former. Moreover, two conventionally used parameters, in literature [15], to assess the level and severity of damage and the resistance of the composite laminates to impact are: (i) the damage degree parameter (DD) and the absorbed energy per delaminated area (E DA /A). These two parameters are widely used for the comparison of composites that possess similar areal density and number of layers, which is the case in this research study.…”
Section: Damage Characterisationmentioning
confidence: 99%
“…A twofold improvement in energy dissipation was reported [1,[11][12][13], owing that to the existence of the z-binding yarns in 3D orthogonal structure. Beside improving the energy absorption, it acts as a restraint to the delamination and structure failure [14,15]. Miao et al [16] explained, utilising the experimental and numerical approaches, that the preventions of the delamination depend on the zig-zag formation of the damages through the composite structure.…”
The effect of the weaving architecture and the z-binding yarns, for 2D and 3D woven composites on the low-velocity impact resistance of carbon fibre reinforced composites, is investigated and benchmarked against noncrimp fabric (NCF). Four architectures, namely: NCF, 2D plain weave (2D-PW), 3D orthogonal: plain (ORT-PW) and twill (ORT-TW), were subjected to 15 J impact using a 16 mm-diameter, 6.7 kg hemispherical impactor. Nondestructive techniques, including ultrasonic C-scanning, Digital Image Correlation (DIC) and X-ray computed tomography (CT) were used to map and quantify the size of the induced barely visible impact damage (BVID). The energy absorption of each architecture was correlated to the damage size: both in-plane and in-depth directions. The 3D architectures, regardless of their unit-cell size, demonstrated the highest impact resistance as opposed to 2D-PW and the NCF. X-ray CT segmentation showed the effect of the higher frequency of the z-binding yarns, in the ORT-PW case, in delamination and crack arresting even when compared to the other 3D architecture (ORT-TW). Among all the architectures, ORT-PW exhibited the highest damage resistance with the least damage size. This suggests that accurate design of the z-binding yarns’ path and more importantly its frequency in 3D woven architectures is essential for impact-resistant composite structures.
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