Chapter 4 Thermoforming of continuous fibre/thermoplastic composite sheets

Friedrich, K.; Hou, Meng; Krebs, Johannes

doi:10.1016/s0927-0108(97)80006-9

Cited by 38 publications

(38 citation statements)

References 23 publications

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“…In the forming process, a hydrostatic pressure is applied to a dry fabric stack via a diaphragm to produce the final preform, similar to the commonly employed preforming step of prepregs for autoclave processing in the aerospace industry [1]. It used to be mainly associated with thermoplastic composite materials [2][3][4], but more recently has been used to process thermoset prepregs [1, [5][6][7] and produce binder-stabilised dry fabric preforms for liquid moulding routes [8][9][10][11].…”

Section: Introductionmentioning

confidence: 99%

Double diaphragm forming simulation for complex composite structures

Chen

McGregor

Endruweit

et al. 2017

Composites Part A: Applied Science and Manufacturing

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A finite element (FE) material model has been developed to simulate the double diaphragm forming (DDF) process, to identify potential defects when forming complex 3D preforms from 2D biaxial non-crimp fabric plies. Three different metrics have been introduced to predict and characterise defects, which include local shear angles to determine ply wrinkling induced by over-shear, compressive strains in the primary fibre directions to determine bundle wrinkling, and tensile stresses in the primary fibre directions to determine fabric bridging . The FE simulation is in good agreement with experiments performed on a demonstrator component. Results indicate that fabric bridging occurs in large-curvature regions, which is the dominant defect in DDF. The axial tensile stress in fibres has been used as a measure to identify suitable positions and orientations for darts, to alleviate fabric bridging and improve surface conformity, whilst minimising the effect on the mechanical performance of the component.

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Section: Introductionmentioning

confidence: 99%

Double diaphragm forming simulation for complex composite structures

Chen

McGregor

Endruweit

et al. 2017

Composites Part A: Applied Science and Manufacturing

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“…This is because matched-die forming shapes a laminate by draping it onto a male die [8]. Research by Hu [28] stated that the phenomenon of wrinkle formation is one of buckling and post-buckling deformations in terms of structural mechanics.…”

Section: Resultsmentioning

confidence: 99%

Formability Analysis of Bamboo Fabric Reinforced Poly (Lactic) Acid Composites

2016

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Poly (lactic) acid (PLA) composites have made their way into various applications that may require thermoforming to produce 3D shapes. Wrinkles are common in many forming processes and identification of the forming parameters to prevent them in the useful part of the mechanical component is a key consideration. Better prediction of such defects helps to significantly reduce the time required for a tooling design process. The purpose of the experiment discussed here is to investigate the effects of different test parameters on the occurrence of deformations during sheet forming of double curvature shapes with bamboo fabric reinforced-PLA composites. The results demonstrated that the domes formed using hot tooling conditions were better in quality than those formed using cold tooling conditions. Wrinkles were more profound in the warp direction of the composite domes compared to the weft direction. Grid Strain Analysis (GSA) identifies the regions of severe deformation and provides useful information regarding the optimisation of processing parameters.

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“…The occurence of out-of-plane wrinkles is complex and has been studied by several researchers. For a given material, experimental studies reported that, amongst other factors, stress conditions induced by manufacturing boundary conditions, forming speeds, original blank dimensions and strain gradients play a role in their development [9,[25][26][27][28]. Considering simulation, Boisse et al also showed that the appearance of out-of-plane wrinkles is a global phenomenon which depends on boundary conditions and all types of strains and stiffness [14].…”

Section: Bending In Fe Forming Simulationsmentioning

confidence: 99%

“…by means of a thermoforming process. Thermoforming is a manufacturing method that consists in forming consolidated customised thermoplastic blanks into complex 3D-geometries using a thermoforming unit [9][10][11]. The combination of pressure and temperature enables the material to deform.…”

Section: Introductionmentioning

confidence: 99%