Damage localization in composite lattice truss core sandwich structures based on vibration characteristics

Abstract Sandwich structures possess a high bending stiffness compared to monolithic structures with a similar weight. This makes them very suitable for lightweight applications where high stiffness to weight ratios are needed. Most common manufacturing methods of sandwich structures involve adhesive bonding of the core material with the sheets. However, adhesive bonding is prone to delamination, a failure mode which is often difficult to detect. In this paper, the results of delamination testing of fully additive manufactured (AM) AlSi10Mg sandwich structures with pyramidal lattice truss core are presented. To characterise the bonding strength, climbing drum peel tests and out-of-plane tensile tests are done. The thickness of the faces and the diameter of the struts is 0.5 mm, while the core is 2 mm thick. The inclination of the struts is 45°. To predict the expected failure loads and modes, analytical formulas are derived. The analytics and tests are supported by finite element (FE) calculations. From the analytic approaches, design guidelines to avoid delamination in AM sandwich structures can be followed. The study shows, that critical ratios for face sheet thickness to strut diameter can be determined, to define if the structure tends to delaminate under certain loads. Those ratios are mainly influenced by the strut inclination. The peel tests resulted in face yielding, which can also be followed from the analytics and numerics. The out-of-plane tensile tests didn't damage the structure.

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The Study of Low-Velocity Impact Characteristics and Residual Tensile Strength of Carbon Fiber Composite Lattice Core Sandwich Structures

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.194-196.117 ◽

2011 ◽

Vol 194-196 ◽

pp. 117-120 ◽

Cited By ~ 2

Author(s):

Xai Mei Lu ◽

Yun Fei Ma ◽

Shi Xun Wang

Keyword(s):

Tensile Strength ◽

Carbon Fiber ◽

Sandwich Structures ◽

Fiber Composite ◽

Low Velocity Impact ◽

Low Velocity ◽

Carbon Fiber Composite ◽

Velocity Impact ◽

Composite Lattice ◽

Lattice Core

In this paper, low-velocity impact characteristics and residual tensile strength of carbon fiber composite lattice core sandwich structures are investigated experimentally and numerically. Low-velocity impact tests and residual tensile strength tests are simulated by the FE (finite element) software, ABAQUS/Explicit and its subroutine (VUMAT). In order to give more detailed description about the impact damage of the structure and improve modeling accuracy, multi-steps analysis method is employed to simulate impact process and residual tensile strength test in one analysis model. The calculation results computed by the FE model have been compared to the value of experiments, the difference of impact process simulation is about 3.3% and that of tensile strength test simulation is about 12.9%. The calculation error of computation model is acceptable, since unavoidable damage could be introduced in the courses of manufacture, processing and transportation of composite materials, and these damages are determinated difficultly in the computation programs. Next, the degradation tendency chart of residual tensile strength and impact energy threshold Uo of carbon fiber composite lattice core sandwich structures are obtained by the computation value of residual tensile strength after impacted with different impact energy. Previously, this threshold can only be obtained by experiment tests. After the contact force which is bigger than the threshold Uo impact on the sandwich structures, the residual tensile strength of structures are degraded greatly. This conclusion is significant for the design and application of carbon fiber composite lattice core sandwich structures.

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