Joining Forces Wales
Producing the finest safety equipment for climbers demands continuous product improvement to ensure optimum design, materials and manufacturing techniques.
North Wales based climbing equipment manufacturer DMM produces the innovative and highly acclaimed Deadman. The main section of this lightweight snow protection device is made from aluminium alloy, Fig.1.
Fig.1. The DMM 'Deadman' aluminium alloy snow protection device. Finite Element Analysis, provided under the Joining Forces Wales programme, has enabled the company to proceed with confidence in the design of its carbon fibre composite version.
Driven by the desire to further reduce the weight of the Deadman - whilst maintaining or enhancing its excellent functionality, strength and durability - the company decided to explore the use of carbon fibre composite instead of aluminium alloy.
With the strength requirements of the Deadman clearly defined, DMM were determined to meet these with the lightest possible composite material. They achieved this goal through technical support from TWI's Joining Forces Wales technology transfer programme, which established how the strength of the Deadman would be affected by the thickness of the composite material as well as the way in which the material was made.
R&D work at TWI involved Finite Element Analysis (FEA). This computer-based method is widely used in engineering to study the effects of impact, vibration and thermal or static loads on components and structures. It can simulate and predict stresses, deformation, temperatures and other important parameters to achieve an understanding of strength and in-service performance.
FEA showed the stresses within the Deadman and predicted its strength in relation to the composite's lay-up, i.e. fibre type and orientation and number of plies (layers) in the composite, including specially positioned reinforcement; Fig.2.
Fig.2. Finite Element Analysis of carbon fibre composite version of the 'Deadman' snow protection device
Benchmark case. This case simulates a rupture test carried out by DMM on a prototype. The load at rupture was 3.8kN against a target of 6.1kN. The maximum stress calculated for this load is then set as a critical level that must not be reached.
Optimisation. By adding strips of material in the highly stressed region, the stress obtained at the target load of 6.1kN is kept below the maximum level determined in the benchmark case.
FEA enabled optimisation of the lay-up to provide the most favourable distribution of stresses and best strength-to-weight performance. This work has allowed DMM to proceed safe in the knowledge that the design of their new carbon fibre Deadman exceeds the standard of excellence demanded by the company.
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Joining Forces Wales is part-financed by the Welsh Assembly Government