scholarly journals Mechanical properties of the wood-based X-type lattice sandwich structure

BioResources ◽  
2020 ◽  
Vol 15 (1) ◽  
pp. 1927-1944 ◽  
Author(s):  
Tengteng Zheng ◽  
Yanpeng Cheng ◽  
Shuai Li ◽  
Yan Zhang ◽  
Yingcheng Hu
Keyword(s):  
Mechanical Properties ◽  
Failure Mode ◽  
Sandwich Structure ◽  
Shear Failure ◽  
Compressive Test ◽  
The Core ◽  
Short Beam ◽  
Out Of Plane ◽  
Beam Shear ◽  
Type Lattice

In this study, a wood-based X-type lattice sandwich structure was fabricated by an insertion glue method using medium density fiberboard (MDF) and plywood as panels. Birch was used for the core. The mechanical properties and failure modes of the wood-based X-type lattice sandwich structure were investigated by an out-of-plane compressive test, a short beam shear test, and their matching analytical models. The out-of-plane compressive test and the compression analytical model showed that the failure mode of the plywood and birch combination was mainly shear failure in the core. The cores were broken or had sliding surfaces, while the failure mode of the MDF and birch combination was mainly shear failure of the core at both ends. Although the compression properties of the MDF and birch combination were better, the specific strength and modulus of the plywood and birch combination was larger, which align with the characteristics of lightweight and strong strength. The failure mode of the plywood and birch combination was delamination at both ends of the panel or core breakage, which indicated that this combination had better short beam shear properties. The theoretical models of the compressive /short beam shear properties were in good agreement with experimental results obtained for the plywood and birch combination.

Shear mechanical properties of the core structure of biomimetic fully integrated honeycomb plates

2018 ◽  
Vol 22 (4) ◽  
pp. 1184-1198 ◽  
Author(s):  
Wanyong Tuo ◽  
Jinxiang Chen ◽  
Mengye Xu ◽  
Zhijie Zhang ◽  
Zhensheng Guo
Keyword(s):  
Mechanical Properties ◽  
Failure Mode ◽  
Shear Failure ◽  
Core Structure ◽  
Resin Matrix ◽  
Joint Interface ◽  
Shear Direction ◽  
Material Interface ◽  
Fully Integrated ◽  
The Core

In the present study, the shear failure mode and mechanical properties of the core structure of biomimetic fully integrated honeycomb plates with sealing edges were investigated experimentally and through the finite element method. The findings are as follows: (1) the failure mode of the sealing edges and honeycomb walls perpendicular to the shear direction is mainly debonding between the fiber and matrix, whereas fiber breakage, debonding between the fiber and matrix and exfoliation of the resin matrix occur in the sealing edges parallel to the shear direction. Meanwhile, the reasonableness and feasibility of the double shear testing apparatus designed in this study were verified, thus confirming the results of research are reliable and valid. (2) Shear failure of the core structure of fully integrated honeycomb plates is mainly fiber debonding appearing in the middle surface of the core structure, which is a failure of the material interface. Stripping failure in the joint interface of the core layer and upper and lower plates does not occur, which indicates that the biological structure possesses excellent integral mechanical properties. (3) The sealing edges parallel to the shear direction and the honeycomb walls that are oriented 30 degrees to the shear direction are the first to fail, followed by the sealing edges and honeycomb walls perpendicular to the shear direction, which is consistent with the microscopic failure phenomenon observed in both directions. To prevent failure at the material interface, the fully integrated honeycomb plates manufactured in this experiment require further improvements. Thus, countermeasures are proposed, such as pre-treating the fiber surface. These findings will specify future research directions to perfect fully integrated honeycomb plates and improve the shear mechanical properties of core structures.

Mechanical Properties of Thermoplastic Composites via In Situ Polymerization from Cyclic Oligomers

2013 ◽  
Vol 750-752 ◽  
pp. 7-10
Author(s):  
Kou An Hao ◽  
Zhen Qing Wang ◽  
Li Min Zhou
Keyword(s):  
Mechanical Properties ◽  
In Situ Polymerization ◽  
High Viscosity ◽  
Thermoplastic Composites ◽  
Thermoplastic Matrix ◽  
Polymerization Catalyst ◽  
Short Beam ◽  
Beam Shear ◽  
Cyclic Oligomers

Fiber impregnation has been the main obstacle for thermoplastic matrix with high viscosity. This problem could be surmounted by adapting low viscous polymeric precursors Woven basalt fabric reinforced poly (butylenes terephthalate) composites were produced via in-situ polymerization at T=210°C. Before polymerization, catalyst was introduced to the reinforcement surface with different concentration. DSC is used to determine the polymerization and crystallization. SEM is used to detect whether the catalyst existed on surface. Both flexural and short-beam shear test are employed to study the corresponding mechanical properties.

IM7/LARC™-IAX-3 Polyimide Composites

1998 ◽  
Vol 10 (2) ◽  
pp. 193-206 ◽  
Author(s):  
T H Hou ◽  
T L St Clair
Keyword(s):  
Mechanical Properties ◽  
High Performance ◽  
Elevated Temperatures ◽  
Flexural Modulus ◽  
Longitudinal Tensile Strength ◽  
Molecular Weights ◽  
Short Beam ◽  
Beam Shear ◽  
Carrier Solvent ◽  
Langley Research Center

LARC™-IAX-3 (Langley Research Center™-improved adhesive experimental resin-3) aromatic polyimide, based on oxydiphthalic anhydride, 3,′4-oxydianiline (3,′4-ODA) and 1,4-phenylenediamine ( p-PDA), was evaluated as a matrix for high-performance composites. Four poly(amide acid) solutions in either N-methypyrrolidone or γ-butyrolactone, end-capped with phthalic anhydride to various theoretical molecular weights, were synthesized. Unidirectional prepreg was fabricated from each of the four resins utilizing NASA-Langley’s multipurpose prepreg machine. The temperature-dependent volatile depletion rates, the thermal crystallization behaviour and the resin rheology were characterized. Based on this information, a composite moulding cycle was developed which consistently yielded well consolidated void-free laminate parts. Composite mechanical properties such as short beam shear strength, longitudinal and transverse flexural strength and flexural modulus, longitudinal tensile strength and notched and unnotched compression strengths were measured at room temperature (RT) and elevated temperatures. Similar properties were obtained independent of the carrier solvent used during matrix resin synthesis. These mechanical properties were superior to those previously measured for IM7/LARC™-IA and IM7/LARC™-IAX composites. The enhanced mechanical properties were attributed to the substitution of 25% 3,′4-ODA by p-PDA in the LARC™-IA imide backbones.

scholarly journals Experimental Study on the Fracture Evolution Processof Rock-like Specimens Containing a Closed RoughJoint Based on 3D-Printing Technology

2020 ◽  
Vol 2020 ◽  
pp. 1-16
Author(s):  
Jiawei Liu ◽  
Haijian Su ◽  
Hongwen Jing ◽  
Chengguo Hu ◽  
Qian Yin
Keyword(s):  
Mechanical Properties ◽  
3D Printing ◽  
Failure Mode ◽  
Shear Failure ◽  
Rock Joints ◽  
Image Correlation ◽  
Printing Technology ◽  
3D Printing Technology ◽  
Joint Inclination ◽  
Joint Length

In order to overcome the disadvantage of traditional joint fabrication method—inability to reproduce the rough surfaces of practical rock joints—3D-printing technology was applied to restructure five kinds of rough joint according to the failure surface formed by the triaxial prepeak unloading test in this study. And uniaxial compression test was carried out on the rock-like specimens containing closed 3D-printing rough joint to study the effects of joint inclination and joint length on the mechanical properties (peak strength, peak strain, elastic modulus, and secant modulus), cracking process, and failure modes. Besides, digital image correlation (DIC) method and acoustic emission (AE) system are used to investigate the whole evolution process of strain fields and crack propagation during loading. It is found that the mechanical parameters decrease first and then go up as the joint inclination increases, while presenting a continuous downward trend with the increase of joint length. Inclination of 45° and the larger joint length bring more extensive reduction to mechanical properties of specimens. Specimens exhibit typical brittle failure characteristics. The failure mode of specimens affected by different joint inclination is tension-shear failure. And the joint scale rises; the failure mode of specimens changes from tensile failure to shear failure. Larger joint scale results in the longer prepeak fluctuation phase on axial stress-strain curves and more dispersed distribution of high-value AE counts.

Compressive effect of jute fiber corrugated lattice sandwich structure

2019 ◽  
Vol 39 (5-6) ◽  
pp. 209-218
Author(s):  
Shuguang Li ◽  
Runsheng Hu ◽  
Jin Cheng ◽  
Yingcheng Hu
Keyword(s):  
Sandwich Structure ◽  
Failure Modes ◽  
Shear Failure ◽  
Jute Fiber ◽  
Factors Affecting ◽  
Specific Strength ◽  
Out Of Plane ◽  
Theoretical Predictions ◽  
Shear Buckling ◽  
The Cost

A lattice sandwich structure mainly consisting of jute fiber and resin epoxy was prepared. Two configurations were established, and six out-of-plane compression experiments were conducted to identify the factors affecting the mechanical properties of the samples. The specific strength of the 2D corrugated lattice truss with the struts at 30° (I1) was 3 times stronger than that of the sample with sandwich struts at 45°. The specific strength of I1 was 3.9 times stronger than that of the Kagome structure prepared using Cu–2%Be. The cost performance with respect to the specific strength of the structure I1 was 161.7 times higher than that of the Kagome structure prepared using Cu–2%Be. Three failure modes were considered, and theoretical predictions were made separately. The failure modes in the experiment were mainly shear failure and shear buckling failure in sandwich struts.

Effect of Moisture Absorption on Mechanical Properties of Resin Transfer Molded Composites

2002 ◽  
Author(s):  
Levent Aktas ◽  
Youssef Hamidi ◽  
M. Cengiz Altan
Keyword(s):  
Mechanical Properties ◽  
Moisture Absorption ◽  
Volume Fraction ◽  
Accelerated Aging ◽  
Fiber Volume ◽  
Fiber Reinforced Polymer Composites ◽  
Short Beam ◽  
Beam Shear ◽  
The Masses ◽  
Fiber Preforms

Fiber reinforced polymer composites are highly susceptible to environmental conditions despite their favorable properties. Among various environmental factors, moisture absorption is known to have significant adverse effects on such materials. This work investigates the effects of accelerated moisture absorption on the mechanical properties of resin transfer molded glass/epoxy composites. 152.4 mm diameter disk-shaped parts are fabricated using EPON 815C resin and EPICURE 3282 curing agent. Reinforcement is provided by four layers of randomly oriented planar glass fiber preforms with 0.459 kg/m2 surface density, yielding approximately 21.2% fiber volume fraction. Samples cut from the molded disks are immersed into boiling water for accelerated aging. The masses of the specimens are measured at periodic intervals to quantity the amount of water absorbed. Tensile and short beam shear tests are performed at different levels of moisture absorption. Mechanical properties are found to decrease as moisture diffused into the material. Fiber pullouts on the surfaces of tested samples show fiber loosening as the cause of material weakening. To investigate the desorption and characteristics, part of the samples are dried at 65°C after the maximum moisture absorption is reached. Total stiffness recovery is observed after desorption but ultimate tensile strenth only recovered by 27.7%, which is 33.4% lower than the initial value.

scholarly journals Exploring the Effect of Asperity Order on Mechanical Character of Joint Specimen from the Perspective of Damage

Geofluids ◽  
2021 ◽  
Vol 2021 ◽  
pp. 1-17
Author(s):  
Zhouhao Yuan ◽  
Yicheng Ye ◽  
Binyu Luo
Keyword(s):  
Mechanical Properties ◽  
Acoustic Emission ◽  
Normal Stress ◽  
Failure Mode ◽  
Shear Failure ◽  
Joint Surface ◽  
Normal Stresses ◽  
Joint Specimen ◽  
Waviness And Unevenness ◽  
Softening Stage

The joint morphology is multiscale. The effect of each asperity order on the mechanical properties of joints is different. The shear mechanical properties of joint specimens are related to its surface damage characteristics. At present, there are still few studies on the effect of roughness on the shearing mechanical properties of joint from the perspective of damage of each asperity order. In this paper, the standard roughness profile was chosen as initial morphology. The standard roughness profile was decomposed into waviness and unevenness by the method combine the ensemble empirical mode decomposition (EEMD) and the cut-off criterion. Then, the joint specimen which contains waviness and unevenness and the specimen which only contains waviness were prepared by the 3D engraving technology. The 40 sets of joint specimens with different asperity order were subjected to direct shear tests under different normal stresses. Based on the 3D scanning technology and ICP iterative method, the damaged area and the damage volume were calculated. Based on the damage volume data and the acoustic emission (AE) data, the effect of asperity order to the joint mechanical behaviour was studied. The results indicate that (1) under low normal stress, the unevenness plays a control role in the failure mode of the joint specimen. Under low normal stress, the joint surface containing only waviness exhibits slip failure, and the joint surface with unevenness exhibits shear failure. With the increase of the normal stress, the failure mode of the specimen containing only waviness changes from slip failure to shear failure; (2) the unevenness controls the damage degree of the joint specimen. The damaged area, damage volume, AE energy rate, and accumulative AE energy of the joint specimen with unevenness are larger than those of the specimen with only waviness, and this difference increases with the normal stress increase; (3) the difference between the joint specimen with unevenness and specimen with only waviness mainly exists in the prepeak nonlinear stage and the postpeak softening stage. The characteristic parameters of acoustic emission generated in the postpeak softening stage of the joint specimen with unevenness are greater than those of the specimen with only waviness. This phenomenon can be used to explain the stress drop difference at the postpeak softening stage; (4) the AE b value can be used to evaluate the damage of joint specimens. Analysing the damage difference of each asperity order under different normal stresses is of great significance to the analysis of the influence of the morphology of the joint surface on the mechanical properties of the joint.

Mechanical properties of unidirectional aligned bagasse fibers/vinyl ester composite

2016 ◽  
Vol 36 (2) ◽  
pp. 157-163 ◽  
Author(s):  
Ayyanar Athijayamani ◽  
Balasubramaniam Stalin ◽  
Susaiyappan Sidhardhan ◽  
Azeez Batcha Alavudeen
Keyword(s):  
Mechanical Properties ◽  
Tensile Strength ◽  
Impact Strength ◽  
Vinyl Ester ◽  
Flexural Modulus ◽  
Tensile Modulus ◽  
Short Beam ◽  
Beam Shear ◽  
The Matrix ◽  
The Impact

Abstract The present study describes the preparation of aligned unidirectional bagasse fiber-reinforced vinyl ester (BFRVE) composites and their mechanical properties such as tensile, flexural, shear and impact strength. Composites were prepared by a hand lay-up technique developed in our laboratory with the help of a hot press. Mechanical properties were obtained for different fiber contents by varying the number of layers. The obtained tensile property values were compared with the theoretical results. The results show that the tensile strength increased linearly up to 44 wt% and then dropped. However, the tensile modulus increased linearly from 17 wt% to 60 wt%. In the case of flexural properties, the flexural strength increased up to 53 wt% and started to decrease. However, the flexural modulus also increased linearly up to 60 wt%. The impact strength values were higher than the matrix materials for all the specimens. The short beam shear strength values were also increased up to 53 wt% and then dropped. The modified Bowyer and Bader (MBB) model followed by the Hirsch model shows a very good agreement with experimental results in both tensile strength and modulus.

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