The relationship between the filament scale phenomena and the macroscopic properties of parts manufactured by fused deposition modelling (FDM) of thermoplastic polymers has been investigated using planar geometry dog bone samples, representing layer by layer lamina in an additively manufactured part. Finite element simulations of the response of the FDM part(s) at multiple length scales (filament to macro) are compared with full field strain data obtained experimentally for different raster angles and filament gaps. The strain field, strain energy density, and effective Young's modulus are evaluated. Principal strains resulting from the applied axial loading shifted from the inner rasters to the contours of the FDM planar sample at certain raster angles as the air gap increased, which significantly decreased the effective usage of the material leading to strain localization and premature part failure. The research presented provides a pathway to an effective multiscale approach to optimise the raster contour fill pattern.
Polymeric composite sandwich structures, often manufactured using a thick foam core material and thin composite facings, are of significant interest in naval applications. This paper summarizes the coupled effect of sea water and low temperature on the mechanical properties of closed cell polymeric H100 foam core material. The study considers the effects of harsh sea environmental conditions on the fracture and deformation behavior of such a foam material under complex loading conditions that include tension, torsion, compression, and true-triaxial stress paths. Mechanical testing techniques are developed using coupon samples of suitable geometry that minimize grip effects on these low density complex foam materials, along with information associated with the observed cross-anisotropic behavior. Interfacial delamination fracture response for the sandwich structures due to the combined effects of sea water and low temperature are evaluated and the associated degradation in critical energy release rate for delamination is found to be substantial. Experimental data for H100 foam cores associated with moisture induced expansional strains are also included.
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