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Failure prediction modeling and optimization of composite structure under impact loading is reported in the paper. A methodology is presented to optimize the composite laminate subjected to impact loading considering fiber arrangement as a design variable and residual velocity as an objective function. The fitness function is evaluated using ABAQUS/Explicit that works on the continuum damage mechanics model. The damage behavior of composites obtained through this model is validated with simulation and experiments. The results show a substantial impact of fiber arrangement on residual velocity, penetration, energy absorption capacity and ballistic limit of the plate. [ABSTRACT FROM AUTHOR]

This paper reports a method to construct the complete constitutive model of carbon fiber‐reinforced plastic (CFRP) by distinguishing the strain rate state and modifying the material stiffness. In quasistatic (low strain rate) compression, the initial nonlinear effect caused by the material defects was described by introducing an nonlinear increasing factor. In dynamic (high strain rate) impact, the nonlinear strengthening effect was described by introducing the dynamic amplification factors of stress and strain based on the reference state. Considering the instantaneous temperature rise obtained from the impact work–temperature generation equation and the influence of temperature on modulus and strength, the coupled thermomechanical constitutive models combining the strain rate effect and the temperature effect were established. The user‐defined material subroutines (VUMAT) were developed, and then these constitutive models were verified by finite element analysis (FEA). Finally, the developed material subroutine was applied to predict the impact penetration of CFRP laminates, and the results show that the opening holes, damage and energy dissipation are in good agreement with the reference experiment. This work comprehensively analyzed the construction method of CFRP constitutive models, which would provide a guidance for the coupled thermomechanical behavior under dynamic impact. Highlights: An anisotropic continuum mechanical constitutive behavior considering strain rate effect and damage evolution behavior was established.A macroscopic anisotropic constitutive model including the coupled impact temperature generation‐mechanical behavior was established.Combined with the incremental finite element method, the three‐dimensional user‐defined material subroutines (VUMAT) were developed and verified.The thermomechanical impact penetration behaviors of CFRP laminates was predicted, and the stress field, temperature field and failure characteristics were visualized. [ABSTRACT FROM AUTHOR]

This paper presents an experimental study on the impact behaviour of composite laminates made of a Dyneema ® woven fabric and four different resin matrices. Three thicknesses of each kind of resin laminate were subjected to impact by a spherical steel projectile in a velocity regime ranging from 100 to 200 m/s. The results revealed that the laminates having flexible matrices performed much better in perforation resistance and energy absorption, but had a greater extent of deformation and damage than the counterparts with rigid matrices. It was found that the matrix rigidity played a crucial role in controlling the propagation of transverse deformation, and thereby the local strain and perforation resistance of laminates. The more rigid matrix restrained the laminate's transverse deformation to a smaller area at a given time, which led to higher local strain and lower perforation resistance. Fibre failure in tension was identified as the dominant failure mechanism for the tested laminates. [ABSTRACT FROM AUTHOR]

This study explored the impact response of two bio-inspired composite laminates with linear and non-linear helicoidal fibre architectures. The helicoidal laminates, together with quasi-isotropic and cross-ply control samples, were fabricated using heterocyclic aramid fibres and tested against a spherical projectile under high impact velocities. The results revealed that helicoidal lay-ups with small rotation angles led to inferior perforation resistance and energy absorption capacity when compared to the quasi-isotropic and cross-ply counterparts. The cross-ply configuration was confirmed as the optimal fibre architecture for impact perforation. Post-impact inspections highlighted that the failure mechanisms of laminates were significantly affected by their lay-ups. The number of fractured fibres was found to reduce with the decrease of inter-ply angle. This was due to the small rotation angles promoted a wedge-in mechanism. Moreover, a smaller angle mismatch resulted in diminished overall delamination area in a laminate. Due to these two effects, therefore, helicoidal lay-up configurations with small inter-ply angles are not recommended for impact-resistant laminates reinforced by tough fibres. • High-velocity impact behaviour of bio-inspired helicoidal laminates is explored. • Helicoidal lay-ups perform worse than quasi-isotropic and cross-ply counterparts. • The decrease of inter-ply angle results in fewer fractured fibres. • The overall delamination area reduces as the inter-ply angle decreases. • Tough fibre helicoidal lay-ups are not ideal for resisting high-velocity impact. [ABSTRACT FROM AUTHOR]

The present paper addresses the development of bio-inspired composite laminates based on the Fibonacci sequence for impact resistant applications. Four methods such as thickness ratio (FT), incremental angle (FI), hybrid (FY) and Fibonacci helicoidal (FH) are devised to create various sets of laminates to exploit the Fibonacci sequence into the laminate design. These methods include controlling of ply group thickness (FT), rotation fiber angle (FI), both thickness and angle (FY), and direct implementation of Fibonacci based helicoidal laminate sequence (FH). The performance of these proposed laminates is analysed by considering ballistic impact loading with six different impact velocities, out of which three are below the ballistic limit of laminates. The behaviour of these laminates under this loading is investigated using an elastic-plastic progressive damage based numerical model. The results obtained through numerical simulation are validated with experimental results and found to be well correlated. The performance of bio-inspired laminates is compared with conventional cross-ply and quasi-isotropic laminates in terms of various parameters such as residual velocity, displacement, energy absorption, peak load, number of plies damaged and delamination. These parameters are correlated by using a level-based methodology and the most versatile method to design Fibonacci based bio-inspired laminates among all methods considered is estimated for all velocities. [ABSTRACT FROM AUTHOR]

The existing damage constitutive models for a composite lamina under impact loading have mainly considered four failure modes: longitudinal fiber failure in tension and compression, matrix failure in tension and compression along the transverse direction. However, when subjected to an impact load in the out-of-plane direction, through-thickness compression failure may also occur in laminates. Therefore, the present paper has established a damage constitutive model considering through-thickness compression failure and has compared it to those constitutive models without such consideration to see the improvement in the impact response analysis and to discuss the necessity of including through-thickness compression damage in the simulation. To this end, impact testing was conducted on manufactured composite panels, and the results were used to validate the finite element simulation of composite laminates under impact. The results showed that the constitutive model with the compression failure mode in the thickness direction had higher accuracy in predicting the impact force, displacement, damage, and energy absorption of laminates. The predicted results by the developed constitutive model showed that through-thickness compression damage indeed occurred in the laminates during the impact process, and it was mainly concentrated in the layers near the impact side. In the layers near the rear side, the tension damage of longitudinal fiber and matrix mainly initiated and developed in the annular region around the impact center on the laminates. [ABSTRACT FROM AUTHOR]

• Novel cubic specimens, 50 × 50 × 50 mm, were designed and manufactured to performed edge-on impacts at ply stacking angles of 0°, 22.5° and 45°. • Impact damage was highly localised and an interplay of various damage mechanisms. The specimen thickness constrained the out-of-plane swelling which caused delamination to be most severe at the outer regions of the impact contact area. • A validated numerical model was developed to accurately predict the impact response and progressive impact damage in the specimens. Thick composite laminates are often required in marine applications to resist high hydrodynamic forces. In this work, damage in thick glass-fibre/epoxy laminates caused by low velocity impacts was investigated experimentally and numerically. Cubic specimens 50 × 50 × 50 mm were manufactured, and the ply stacking directions were orientated at 0°, 22.5° and 45° to the impact plane. The impact damage was localised in the vicinity of the impactor contact area and included an interplay of fibre crushing, matrix cracks, matrix plasticity, and delaminations. Finite element modelling predicted the impact response and the type of damages. The model also quantified the primary energy absorption mechanisms which were by fibre crushing, matrix plasticity and propagation of delamination cracks. The highest impact damage resistance was obtained with the 0° (in-plane) specimen due to the fibres being aligned to the impact loading direction. [ABSTRACT FROM AUTHOR]

• Influence of impactor mass on impact behaviour of pultruded composites is studied. • Both external and internal damage characteristics are comparatively analysed. • A precursor damage mode to ultimate failure is observed for pultruded composites. This paper reports on the results of an experimental study on glass fibre reinforced polymer (GFRP) pultruded profiles subjected to low-velocity impact loading. The effects of impactor mass on the impact response of pultruded composites were investigated. Composite specimens were tested under two series of loading conditions using a drop-weight impact facility. The first set of tests was conducted with different impactor masses (i.e. 5.5, 10.5, 15.5 and 20.5 kg) under the same impact energy of 67 J. The specimens in the second set were subjected to varying impactor masses of 6, 12, 24 and 36 kg at the same initial velocity of 4.4 m/s, resulting in different impact energies. The internal and external damage of pultruded composites was analysed to compare the failure mechanisms, including matrix cracking, delamination, and fibre breakage, as functions of the initial impact energy. The results showed that the extent of impact-induced damage increased with ascending impact energies (ascending impactor masses) up to the point at which the specimen was perforated. The initial impact energy was the dominant parameter that controlled the damage tolerance characteristics of pultruded composites. Furthermore, it was found that a significant longitudinal crack was a precursor to ultimate failure. [ABSTRACT FROM AUTHOR]