scholarly journals Development of a Reactive Polyurethane Foam System for the Direct Sandwich Composite Molding (D-SCM) Process

2021 ◽  
Vol 5 (4) ◽  
pp. 104
Author(s):  
Felix Behnisch ◽  
Viktoria Lichtner ◽  
Frank Henning ◽  
Philipp Rosenberg
Keyword(s):  
Polyurethane Foam ◽  
Sandwich Structures ◽  
Lightweight Design ◽  
Sandwich Composite ◽  
Preliminary Evaluation ◽  
Foam Core ◽  
Fiber Reinforced ◽  
Fiber Volume ◽  
Suitable Material ◽  
Composite Molding

Sandwich structures utilize the geometric stiffening effect by increasing the area moment of inertia. This reduces carbon fiber (CF) material within CF-reinforced plastic (CFRP) components, and thus, the CO2 footprint. A suitable material combination for lightweight design is the use of continuous fiber-reinforced face sheets with a light foam core. CFRP sandwich structures with foam core are manufactured by combining a prefabricated foam core with fiber-reinforced cover layers in a two-step press process. Besides the reduction of the used CFRP material, more efficient manufacturing processes are needed. The aim of this paper is to develop a novel polyurethane foam system to enable the direct sandwich composite molding (D‑SCM) process for the production of CFRP sandwich structures by utilizing the resulting foaming pressure during the reactive polyurethane (PUR) foam system expansion for the impregnation of the CF reinforced face sheets. The developed formulation enables D-SCM structures with 150–250 kg/m3 foam density and 44–47.5% fiber volume content, based on a preliminary evaluation.

Experimental and Analytical Study on the Mechanical Behavior of Stitched Sandwich Composite Panel with a Foam Core

2008 ◽  
Vol 33-37 ◽  
pp. 477-482 ◽  
Author(s):  
Xi Tao Zheng ◽  
Jian Feng Zhang ◽  
Fan Yang ◽  
Ya Nan Chai ◽  
Ye Li
Keyword(s):  
Finite Element ◽  
Mechanical Behavior ◽  
Fiber Volume Fraction ◽  
Volume Fraction ◽  
Sandwich Composite ◽  
Composite Panels ◽  
Foam Core ◽  
Compression Tests ◽  
Fiber Volume ◽  
Yarn Diameter

To quantify the effect of structural through-thickness reinforcement in foam core sandwich composite panels, an experimental study was carried out which included three-point bending tests, core shear tests, flatwise tensile and compression tests, as well as edgewise compression tests. Standard test procedures based on ASTM guidelines are followed to test the behavior of the stitched panels with reinforcement at 90 degree orientation with respect to the sandwich faces. The test specimens were manufactured by using polyurethane foam Rohacell 71 IG and carbon fiber reinforced composite facesheets. The dry perform facesheets and foam core were then assembled in a dry lay-up already stitched. Kevlar 29 yarn was used to stitch both sets of panels. The results showed a significant effect of the stitching on the in-plane Young’s modulus which was attributed to local displacements of the in-plane fibers and changes in the fiber volume fraction. Stitching of sandwich panels significantly increases the maximum failure loads under flexure, core shear, flatwise tensile, flatwise compression, and edgewise compression loading. A finite element based unit-cell model was developed to estimate the elastic constants of structurally stitched foam core sandwich composite panels taking into consideration the yarn diameter, the stitching pattern and direction as well as the load direction. Depending on these parameters, local changes of the fiber volume fraction as well as regions with undisturbed and disturbed fiber orientations within the laminate plies are taken into account. A good match between the finite element modeling and the experimental data was obtained. The present work should be considered as a step towards developing a more sophisticated numerical model capable of describing mechanical behavior of sandwich structures.

scholarly journals Determining effective interface fracture properties of 3D fiber reinforced foam core sandwich structures

2018 ◽  
Vol 37 (7) ◽  
pp. 490-503 ◽  
Author(s):  
Zachary T Kier ◽  
Anthony M Waas
Keyword(s):  
Cantilever Beam ◽  
Sandwich Structure ◽  
Double Cantilever Beam ◽  
Sandwich Structures ◽  
Interface Fracture ◽  
Mode I ◽  
Foam Core ◽  
Fiber Reinforced ◽  
Fracture Test ◽  
Fracture Properties

Foam core sandwich composites are finding a wider use in aerospace, automotive, and construction applications. These structures present unique challenges in terms of material failure and interaction and are sensitive to damage and imperfections introduced during manufacturing. An emerging class of 3D fiber reinforced foam core aims to replace monolithic foams used in sandwich structure cores particularly in demanding high-performance aerospace applications. This research is focused on investigating the development of testing methods capable of measuring the effective interface fracture properties between the facesheet and the core in 3D fiber reinforced foam cores. Double cantilever beam and end-notched flexure specimens are developed to evaluate the mode I and mode II fracture properties of a 3D fiber reinforced foam core. The design, development, and initial failure of a mode I interface fracture test for 3D fiber reinforced foam cores are presented. The digital image correlation results on the failed tests allowed for a different approach to be utilized in designing a new bonded double cantilever beam specimen for testing the mode I fracture of a 3D fiber reinforced foam core sandwich structure that resulted in a successful interface fracture test. The bonded DCB specimens exhibited relatively smooth crack propagation and produced GIc values similar to honeycomb sandwich structures and significantly higher than comparable foam structures.

scholarly journals Simulation of RIM-process for Polyurethane Foam Expansion in Fiber Reinforced Sandwich Structures

Procedia CIRP ◽  
2017 ◽  
Vol 66 ◽  
pp. 62-67 ◽  
Author(s):  
Jürgen Tröltzsch ◽  
Kay Schäfer ◽  
Dariusz Niedziela ◽  
Ikenna Ireka ◽  
Konrad Steiner ◽  
...  
Keyword(s):  
Polyurethane Foam ◽  
Sandwich Structures ◽  
Fiber Reinforced ◽  
Foam Expansion

scholarly journals Flexural Behavior of Sandwich Composite Made of JFRP Honeycomb as Core and GFRP as Skin

2020 ◽  
Vol 01 (04) ◽  
pp. 111-115
Author(s):  
Md. Rakibul Islam ◽  
Md Arifuzzaman ◽  
Asif Karim Neon ◽  
Md. Shahe Duzzaman ◽  
Md. Rafiul Islam
Keyword(s):  
Energy Absorption ◽  
Polymer Composite ◽  
Sandwich Structures ◽  
Fiber Reinforced Polymer ◽  
Flexural Behavior ◽  
Face Sheet ◽  
Sandwich Composite ◽  
Fiber Reinforced ◽  
Steel Mold ◽  
Reinforced Polymer

The increasing demand of lightweight, strong and sustainable materials in aerospace, automobile and marine sectors is leading towards the development of new materials and structures. The sandwich composite is one of them which is well-known for their high strength to weight ratio and the fiber based sandwich structures with cellular core show comparatively good mechanical, acoustic, thermal and energy absorption properties than metallic cellular structure. The purpose of this work is to fabricate a sandwich structure with jute fiber reinforced polymer composite (JFRP) as core and glass fiber reinforced polymer composite (GFRP) as face sheet and to investigate bending properties of the fabricated structures for varying face sheet thicknesses. Skin and core honeycomb strips of the sandwich composites were manufactured using hand layup method and steel mold was used to obtain honeycomb shape. Flexural test results show that face sheet thickness has significant effect on the flexural behavior such as peak load, flexural strength and energy absorption. The failure mechanism during bending tests were also identified which would serve as a basis for future improvement of manufactured composites. The delamination at the interface between the core and the face sheet was the first catastrophic failure during bending. The presented sandwich structures are able to carry a significant amount of load even after failure.

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