scholarly journals Voids in fiber-reinforced polymer composites: A review on their formation, characteristics, and effects on mechanical performance

2018 ◽  
Vol 53 (12) ◽  
pp. 1579-1669 ◽  
Author(s):  
Mahoor Mehdikhani ◽  
Larissa Gorbatikh ◽  
Ignaas Verpoest ◽  
Stepan V Lomov
Keyword(s):  
Mechanical Performance ◽  
Void Formation ◽  
Thermomechanical Properties ◽  
Research Field ◽  
Liquid Composite Molding ◽  
Fiber Reinforced ◽  
Manufacturing Defects ◽  
Advantages And Disadvantages ◽  
Mechanical Effects ◽  
Manufacturing Techniques

Voids, the most studied type of manufacturing defects, form very often in processing of fiber-reinforced composites. Due to their considerable influence on physical and thermomechanical properties of composites, they have been extensively studied, with the focus on three research tracks: void formation, characteristics, and mechanical effects. Investigation of voids in composites started around half a century ago and is still an active research field in composites community. This is because of remaining unknowns and uncertainties about voids as well as difficulties in their suppression in modern manufacturing techniques like out-of-autoclave curing and parts with high complexity, further complicated by increased viscosity of modified resins. Finally, this is because of the increasing interest in realization of more accurate void rejection limits that would tolerate some voidage. The current study reviews the research on formation, characterization, and mechanical effects of voids, which has been conducted over the past five decades. Investigation and control of void formation, using experimental and modeling approaches, in liquid composite molding as well as in prepreg composite processing are surveyed. Techniques for void characterization with their advantages and disadvantages are described. Finally, the effect of voids on a broad range of mechanical properties, including inter-laminar shear, tensile, compressive, and flexural strength as well as fracture toughness and fatigue life, is appraised. Both experimental and simulation approaches and results, concerning voids' effects, are reviewed.

Manufacturing Issues and the Resulting Complexity in Modeling of Additively Manufactured Metallic Microlattices

2016 ◽  
Vol 853 ◽  
pp. 394-398 ◽  
Author(s):  
M.G. Rashed ◽  
Mahmud Ashraf ◽  
Paul Jonathan Hazell
Keyword(s):  
Numerical Simulation ◽  
Physical Properties ◽  
Structural Integrity ◽  
Mechanical Performance ◽  
Research Topic ◽  
Powder Bed ◽  
Manufacturing Defects ◽  
Service Load ◽  
3D Printed ◽  
Manufacturing Techniques

Although metallic microlattice material is a sought after research topic currently, it suffers from manufacturing defects such as micro-voids formation due to missed fusion, stemmed from the stacking-layered-fused nature of the metal powder in Powder Bed Fusion (PBF) process. These defects result in weakening of the finished part and reduced mechanical performance under service load, possibly leading to low fatigue strength, and raise serious question about 3D printed structural integrity. Numerical simulation of the built parts also becomes difficult due to irregular physical properties including geometry and anisotropic nature of mechanical properties. This paper provides an overview on the manufacturing issues and the subsequent hurdle faced in numerical simulation of metallic microlattices. While the issues in manufacturing are related to emerging additive manufacturing techniques and out of control of end users, it has been suggested that the limitations in numerical simulation can be overcome by employing advanced approaches, in both physical properties measurement and modeling.

scholarly journals A Review of Biomaterials and Scaffold Fabrication for Organ-on-a-Chip (OOAC) Systems

2021 ◽  
Vol 8 (8) ◽  
pp. 113
Author(s):  
Luana A. Osório ◽  
Elisabete Silva ◽  
Ruth E. Mackay
Keyword(s):  
Clinical Trials ◽  
Cellular Tissue ◽  
Research Field ◽  
Poor Correlation ◽  
Animal Testing ◽  
Engineering Research ◽  
Advantages And Disadvantages ◽  
Organ On A Chip ◽  
Manufacturing Techniques

Drug and chemical development along with safety tests rely on the use of numerous clinical models. This is a lengthy process where animal testing is used as a standard for pre-clinical trials. However, these models often fail to represent human physiopathology. This may lead to poor correlation with results from later human clinical trials. Organ-on-a-Chip (OOAC) systems are engineered microfluidic systems, which recapitulate the physiochemical environment of a specific organ by emulating the perfusion and shear stress cellular tissue undergoes in vivo and could replace current animal models. The success of culturing cells and cell-derived tissues within these systems is dependent on the scaffold chosen; hence, scaffolds are critical for the success of OOACs in research. A literature review was conducted looking at current OOAC systems to assess the advantages and disadvantages of different materials and manufacturing techniques used for scaffold production; and the alternatives that could be tailored from the macro tissue engineering research field.

scholarly journals Preparation of Long Sisal Fiber-Reinforced Polylactic Acid Biocomposites with Highly Improved Mechanical Performance

Polymers ◽  
2021 ◽  
Vol 13 (7) ◽  
pp. 1124
Author(s):  
Zhifang Liang ◽  
Hongwu Wu ◽  
Ruipu Liu ◽  
Caiquan Wu
Keyword(s):  
Mechanical Properties ◽  
Polylactic Acid ◽  
Mechanical Performance ◽  
Tensile Elongation ◽  
Sisal Fiber ◽  
Fiber Reinforced ◽  
Impact Performance ◽  
The Matrix ◽  
Blending Process ◽  
Extension Direction

Green biodegradable plastics have come into focus as an alternative to restricted plastic products. In this paper, continuous long sisal fiber (SF)/polylactic acid (PLA) premixes were prepared by an extrusion-rolling blending process, and then unidirectional continuous long sisal fiber-reinforced PLA composites (LSFCs) were prepared by compression molding to explore the effect of long fiber on the mechanical properties of sisal fiber-reinforced composites. As a comparison, random short sisal fiber-reinforced PLA composites (SSFCs) were prepared by open milling and molding. The experimental results show that continuous long sisal fiber/PLA premixes could be successfully obtained from this pre-blending process. It was found that the presence of long sisal fibers could greatly improve the tensile strength of LSFC material along the fiber extension direction and slightly increase its tensile elongation. Continuous long fibers in LSFCs could greatly participate in supporting the load applied to the composite material. However, when comparing the mechanical properties of the two composite materials, the poor compatibility between the fiber and the matrix made fiber’s reinforcement effect not well reflected in SSFCs. Similarly, the flexural performance and impact performance of LSFCs had been improved considerably versus SSFCs.

Mechanical performance and moisture absorption of various natural fiber reinforced thermoplastic composites

2013 ◽  
Vol 130 (2) ◽  
pp. 969-980 ◽  
Author(s):  
Nicole-Lee M. Robertson ◽  
John A. Nychka ◽  
Kirill Alemaskin ◽  
John D. Wolodko
Keyword(s):  
Moisture Absorption ◽  
Mechanical Performance ◽  
Natural Fiber ◽  
Thermoplastic Composites ◽  
Fiber Reinforced

Experimental study of saturation by visible light transmission in dual-scale fibrous reinforcements during composite manufacturing

2017 ◽  
Vol 36 (23) ◽  
pp. 1693-1711 ◽  
Author(s):  
F LeBel ◽  
É Ruiz ◽  
F Trochu
Keyword(s):  
Visible Light ◽  
Light Transmission ◽  
Void Formation ◽  
In Situ Monitoring ◽  
Injection System ◽  
Computer Assisted ◽  
Liquid Composite Molding ◽  
Composite Molding ◽  
The Impact ◽  
Dual Scale

A new in situ monitoring strategy is proposed to study void formation during real-time impregnation of dual-scale fibrous reinforcements in liquid composite molding. Void content data from burn-off tests are used to calibrate a refractive index matching approach based on two optical principles: Beer–Lambert and Fresnel laws. Once calibrated, this approach based on visible light transmission is used to study the impact of key process parameters on the saturation footprint of dual-scale fibrous reinforcements during and after mold filling. The injection parameters investigated are the flow front velocity, the pressure distribution inside the mold cavity, the bleeding flow rate, and the mold packing pressure. The experimental setup is a computer-assisted injection system and a transparent resin transfer molding mold is used to perform unidirectional injections. A vinyl ester resin is injected through E-glass bidirectional non-crimp fabrics under various manufacturing conditions. This investigation not only confirms the decreasing trend in void formation by mechanical entrapment of air with the decrease in impregnation velocity, as it converges toward the optimal impregnation conditions for this fibrous reinforcement reported in previous studies, but it also brings insights on void dissolution and transport in liquid composite molding.

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