Abstract
Clamped rectangular orthogonal 3D woven carbon composite beams under ballistic impact at a velocity range 60ms-1⩽v0⩽190ms-1 were investigated in order to understand the damage mechanisms within the material and the role of through-the-thickness (TTT) reinforcement. Experimental tests revealed three distinct categories of beam response: (i) low velocity impacts (v0<110ms-1) which featured projectile rebound, with dominant matrix cracking and localised fibre fracture, (ii) medium velocity impact (110ms-1⩽v0<148ms-1) which exhibited a stretch-deformation dominated failure mechanism, and (iii) higher velocity impacts (v0⩾148ms-1) which resulted in projectile penetration, combined with longitudinal fibre fracture at the centre of the sample. Finite element (FE) simulations were conducted to understand the experimental outcomes, which showed sufficient fidelity and captured the three distinct beam response regimes. The presence of the TTT-reinforcement can suppress the inter-laminar matrix crack propagation and increase the material ballistic impact resistance for low velocity impact and high velocity impact. However, for medium velocity impact, the in-plane fibre fracture surface was found to be at the locations of TTT-reinforcement. This may suggest that the TTT-reinforcement creates weak points for the stretch-deformation dominated failure mechanism. The verified FE simulations were conducted to predict the multi-hit ballistic impact limit surfaces for the clamped circular 3D woven composite plates, and for the equivalent laminate composite without the presence of the TTT reinforcement. The numerical results suggested the presence of TTT reinforcement could improve the multi-hit ballistic resistance of the composite plates for multi-hit scenarios where the initial impact is 50%–95% of the ballistic limit of the plates.
Highlights
The dynamic impact of foreign objects upon aircraft structures is of great concern and is often a critical load case for design engineers to consider
Ballistic impact experimental tests on clamped rectangular 3D woven carbon composite beam samples were undertaken in order to understand the damage mechanisms within the material and the role of the through-the-thickness (TTT) reinforcement
Detailed Finite element (FE) simulations were conducted for interpretation and verification purposes, which were shown to have sufficient fidelity in order to capture the characteristic damage modes of the three response types
Summary
The dynamic impact of foreign objects upon aircraft structures is of great concern and is often a critical load case for design engineers to consider. A different study, by impacting clamped samples with a 0.30 calibre fragment simulating projectile, recorded a 5% reduction in ballistic limit for the orthogonal 3D woven composite in comparison with a 2D plain weave carbon composite [16]. A numerical study has been conducted by Ghosh and De [4] to identify how the through-thethickness (TTT) reinforcement in the orthogonal 3D woven composite can influence the ballistic response of a composite plate. The methodology will be used to characterise the multi-hit behaviour of orthogonal 3D woven carbon composite plates, alongside with that of the equivalent cross-ply laminate plates for comparison.
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