F Souza, L Castro, K Neves, L Lima, H Cornwell
Keywords: multiscale, simulation, composite, advanced materials, microstructures, failure models
Summary:Finite element analysis has become increasingly important for mechanical design and the development of new advanced materials. Being able to predict structural performance accurately and efficiently can circumvent the extensive time and cost of repetitive and rigorous material testing. However, with materials becoming more complex, the assumption of homogeneity as well as generalizing a material based on global properties does not sufficiently describe a structure close to failure. The key to accurately predict material failure is to realistically capture microstructural damage, but to capture this at a length scale orders of magnitude smaller than the full scale part is impossible with the drastic increase in computation time - it is not even possible to mesh it. In a wide variety of industries, unidirectional fiber reinforced composites are being utilized for high pressure containers and tubes, in which the high axial strength fibers can bear the majority of the hoop stress. To accurately predict the burst pressure of tubes, a finite element model must be able to incorporate defects from the composite manufacturing process, such as voids, resin pockets, variations in fiber volume fraction, and progressive damage. The challenge lies in modeling such microstructural features, which are at a length scale orders of magnitude smaller than the full product scale, as well as linking the microstructural models back to the product performance. For a thermoplastic unidirectional carbon fiber composite tube, MultiMech has demonstrated the ability to account for such microstructural mechanisms and process induced variation to more reliably predict the burst pressure and localized stresses within the composite. MultiMech utilizes a proprietary TRUE MultiscaleTM technology, a fully coupled two-way multiscale FE solver with the ability to accurately predict global structural failure based on microstructural design variables, without significant increase in computation time. For the thermoplastic composite tube, different defects such as voids and resin pockets were defined and stochastically inserted into the model to characterize a range of manufacturing variability. Because the defects are inserted randomly, multiple simulations can be run for each scenario to obtain a lower and upper limit of burst pressures for different tubes comprised of different types of defects and different percentages of defects. When compared to experimental evidence, the results demonstrate the robustness of the TRUE MultiscaleTM approach by its notably accurate predictions as well as speed in generating the results for such a nonlinear failure problem. This paper with demonstrate how MultiMech’s TRUE MultiscaleTM technology can enable composite tube manufacturers to quickly and accurately predict product performance without the need to fabricate and test multiple physical prototypes, thus saving substantial amount of time and cost.