Stretch forming studies on a fibre metal laminate based on a self-reinforcing polypropylene composite

This paper investigates the room temperature formability of a fibre metal laminate system comprised of aluminium and a self-reinforcing polypropylene composite. Blanks of varying geometry were stretch formed over a hemispherical punch in a custom built stamping press. A real-time three-dimensional photogrammetric measuring system was used to acquire the evolution of surface strain and the strain at failure during forming. The results from this work illustrate that these advanced light weight material systems are amenable to mass production through stamp forming. A significant finding from this work is that these material systems can exhibit forming characteristics that are comparable and sometimes superior to metal forming

The Influence of Strain Rate on the Mode III Interlaminar Fracture of Composite Materials

The Mode III interlaminar fracture toughness, GIIIc, of composite materials based on both thermoplastic and thermosetting-matrices have been investigated using the edge crack torsion (ECT) test geometry. Tests were undertaken at room temperature and ove

The mechanical properties of corrugated core structures based on flax fibre composites

Background: The mechanical properties of novel flax fibre reinforced corrugated composite structures subjected to quasi-static and dynamic compression loading are investigated in this paper. Polypropylene (PP) and polylactic acid (PLA) have been used as thermoplastic matrices to enhance the recyclability of the composite material. Methods: The corrugations were manufactured using matched-die compression moulding and then used as cores in sandwich panels having facings of the same material. The effect of increasing the number of corrugations on the compressive properties of the sandwich panels was investigated by subjecting them to compression loading. Results: The results indicated a monotonic increase in the absorbed energy as the number of corrugations increased from two to five. All of the panels based on flax/PP composites showed a greater energy- absorbing capability compared to those made from flax/PLA. Conclusion: The cores exhibited progressive cell-wall buckling and cell wall folding, characteristic of a typical energy-absorbing structure. The predominant mode of failure was buckling, and then cell wall fracture for the flax/PP corrugations in contrast to interlaminar delamination, and fibre buckling for the flax/PLA cores. Failure maps indicate that the cell walls buckle at low relative densities (up to 0.01) with cell wall fracture occurring at higher relative densities. At the balanced relative density, where both buckling and fracture of the cell walls occur simultaneously, the corresponding stresses are 0.8 MPa for the flax/PLA composite and 0.6 MPa for flax/PP composite. The associated relative density is about 0.01 for both cases

A Parametric Study of the Low-Impulse Blast Behaviour of Fibre-Metal Laminates Based on Different Aluminium Alloys

A parametric study has been undertaken in order to investigate the influence of the properties of the aluminium alloy on the blast response of fibre-metal laminates (FMLs). The finite element (FE) models have been developed and validated using experi-mental data from tests on FMLs based on a 2024-O aluminium alloy and a woven glass-fibre/polypropylene composite (GFPP). A vectorized user material subroutine (VUMAT) was employed to define Hashin’s 3D rate-dependant damage constitutive model of the GFPP. Using the validated models, a parametric study has been carried out to investigate the blast resistance of FML panels based on the four aluminium alloys, namely 2024-O, 2024-T3, 6061-T6 and 7075-T6. It has been shown that there is an approximation linear relationship between the dimensionless back face displacement and the dimensionless impulse for all aluminium alloys investigated here. It has also shown that the residual displacement of back surface of the FML panels and the internal debonding are dependent on the yield strength of the aluminium alloy

Towards a rapid, non-contact shaping method for fibre metal laminates using a laser source

Abstract Since their initial development, fibre metal laminates (FMLs) have slowly started to be used by industry, particularly the aerospace sector. One of the reasons for the relatively slow adoption of FMLs is due to the difficulties faced in shaping them to the desired geometry. Whilst traditional processes such as roll forming are effective in shaping monolithic materials, these processes could potentially destroy the mechanical properties of the composite layer. The approached investigated here uses thermal or laser forming (LF) to shape flat panels of thermosetting glass fibre based FMLs into 2D geometries. This initial empirical investigation covers the effectiveness of the various LF processes and the effects of various parameters have on the forming process. These include laser parameters such as power and velocity and material parameters such as FML lay-up strategy, fibre orientation and comparison with monolithic materials

Tapping a Foreign Subsidiarys Competence: An Empirical Test of Subsidiaries of Multinational Corporations in South Korea

This study examined the conditions under which a foreign subsidiary becomes the competence center within the multinational corporation (MNC)s network. We developed an integrated framework by investigating effects of both subsidiary-level factors and headquarter (HQ)-level factors on subsidiarys competence development. Survey data from 76 foreign subsidiaries of MNCs in South Korea largely supported our hypotheses. We found that subsidiaries with high management autonomy and high network embeddedness in the local market (South Korea) tend to build superior capabilities that would be useful throughout the entire MNC network. Concerning an MNCs management system, our results suggested that technological and managerial knowledge transfer from HQ to subsidiaries plays important roles in helping a subsidiary evolve into a competence center in the MNCs global network