Lendinez Torres, Angela
(2025)
Understanding the double diaphragm forming process: moving towards multi-component forming.
PhD thesis, University of Nottingham.
Abstract
Composite materials, formed by combining two or more distinct constituents, offer superior mechanical properties compared to traditional materials, making them essential in industries such as automotive, aerospace, and renewable energy. In advanced manufacturing processes, double diaphragm forming enables the transformation of 2D dry fabric blanks into 3D structures. However, this process presents challenges, including defect formation such as wrinkling and bridging, which can compromise the structural integrity of the final component. As sustainability and process efficiency become increasingly critical, optimising forming techniques is essential. This research focusses on non-crimp fabrics due to their superior mechanical properties and structural performance, investigating key factors influencing defect formation and exploring strategies to enhance the efficiency and sustainability of the double diaphragm forming process.
This thesis aims to enhance the understanding of the double diaphragm forming process and to assess the feasibility of multi-component forming. Established numerical and experimental methodologies were used to explore the effect of key parameters on defect formation. Multi-component forming was evaluated to investigate the effect of fabric and diaphragm interactions, with the goal of improving the sustainability and efficiency of the process.
An experimental and numerical methodology were established, defining mesh configuration, mass scaling and material parameters for the numerical model. The numerical predictions were validated against experimental results, with the model providing valuable insights, but further refinement is required to improve defect prediction accuracy.
The influence of process parameters, including diaphragm size, breather configuration, two-step preforming, stacking sequence and modelling of the breather were explored. Diaphragm size significantly influences wrinkling patterns, with optimal dimensions ranging between 500 mm and 1000 mm or 1300 mm, depending on the fabric orientation. Breather positioning affects material draping, with placement in non-draping areas reducing wrinkling.
Two-step preforming reduced wrinkling severity but did not decrease the number of wrinkles, making it less cost-effective due to increased labour and material use. Stacking sequence also played a key role, with a 0⁰ relative fibre angle minimising the severity of wrinkles, whereas a 45⁰ angle was more likely to induce severe wrinkling. Including the breather in the numerical model improved defect predictions, aligning wrinkling patterns more closely with experimental observations, though conformity to tool remained underpredicted.
The last chapter of the thesis explored fabric and diaphragm interactions to assess the feasibility of simultaneous multi-component forming. Studies were conducted using two and three hemispherical tools of different size.
Results indicated that forming two preforms simultaneously reduced draping and required precise in-plane spacing. A horizontal spacing of 200 mm to 600 mm between the fabric edges was optimal, while a vertical spacing below 100 mm between the edge of one fabric and the centre of another improved forming due to proximity to the diaphragm edge. Additionally, specific orientations and forming two hemispheres of different radii was found to be beneficial to the forming process.
For three tool forming, fabric positioning critically influenced defect patterns. Increasing spacing in the x-direction generally improved conformity of fabrics 1 and 2, while increasing spacing in the y-direction was more beneficial for fabric 3.
| Item Type: |
Thesis (University of Nottingham only)
(PhD)
|
| Supervisors: |
Warrior, Nicholas A. |
| Keywords: |
Composite materials; Double diaphragm forming; Defect formation; Multi-component forming |
| Subjects: |
T Technology > TS Manufactures |
| Faculties/Schools: |
UK Campuses > Faculty of Engineering > Department of Mechanical, Materials and Manufacturing Engineering |
| Item ID: |
80597 |
| Depositing User: |
Lendínez Torres, Ã�ngela
|
| Date Deposited: |
31 Jul 2025 04:40 |
| Last Modified: |
31 Jul 2025 04:40 |
| URI: |
https://eprints.nottingham.ac.uk/id/eprint/80597 |
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