The delamination process in thin composite plates subjected to low-velocity impact is simulated using a specially developed 2D cohesive/volumetric finite element scheme. Cohesive elements are introduced along the boundaries of the inner layers and inside the transverse plies to simulate the spontaneous initiation and propagation of transverse matrix cracks and delamination fronts. The analysis is performed within the framework of the finite deformation theory of elasticity to account for the nonlinear stiffening of the thin composite plate and the large rotations which accompany the fracture process. The simulation is dynamic and uses an explicit time stepping scheme. Comparison with existing experiments performed on graphite/epoxy laminates indicates that the cohesive/volumetric finite element scheme is able to capture the complex mechanisms leading to the delamination, including the initial micro-cracking of the matrix, the appearance of critical transverse matrix cracks and the rapid propagation of delamination cracks initiated at the intersections between the critical matrix cracks and the adjacent plies.

Impact-induced delamination of composites: A 2D simulation

A finite element formulation is presented for modeling the dynamic as well as static response of laminated composites containing distributed piezoelectric ceramics subjected to both mechanical and electrical loadings. The formulation was derived from the variational principle with consideration for both the total potential energy of the structures and the electrical potential energy of the piezoceramics. An eight-node three-dimensional composite brick element was implemented for the analysis, and three-dimensional incompatible modes were introduced to take into account the global bending behavior resulting from the local deformations of the piezoceramics. Experiments were also conducted to verify the analysis and the computer simulations. Overall, the comparisons between the predictions and the data agreed fairly well. Numerical examples were also generated by coupling the analysis with simple control algorithms to control actively the response of the integrated structures in a closed loop.

Finite element analysis of composite structures containing distributed piezoceramic sensors and actuators

An investigation was performed to study the impact damage of graphite/epoxy laminated composites caused by a low-velocity foreign object. The impact damage in terms of matrix cracking and delaminations resulting from a point-nose impac tor was the primary concern. A model was developed for predicting the initiation of the damage and the extent of the final damage as a function of material properties, laminate configuration and the impactor's mass. The model consists of a stress analysis and a failure analysis. A transient dynamic finite element analysis was adopted for calculating the stresses and strains inside the composites during impact resulting from a point-nose im pactor. Failure criteria were proposed for predicting the initial intraply matrix cracking and the size of the interface delaminations in the composites. Experiments were also per formed to verify the model and the computer simulations. The predictions agreed fairly well with the test data.

A Model for Predicting Damage in Graphite/Epoxy Laminated Composites Resulting from Low-Velocity Point Impact

An investigation comprised of experiments and analysis was performed to study impact damage in laminated composites caused by low-velocity impact The major objective of the study was to fundamentally understand the failure mechanisms and mechanics of fiber-reinforced composites resulting from impact and to identify the essential parameters governing the impact damage Matrix cracks and delaminations were the primary concern of the studyThis paper emphasizes the experimental work of the study A unique and special air-pressed impact tester was designed and built for the investigation The major characteristics of the tester was the design of a rectangular barrel and a rectangular based impactor rather than a small circular barrel and a spherical ball, which are commonly adopted for impact study This new design allows the user to control the impact damage patterns by appropriately selecting different shapes and sizes of the noses which are mounted to the base of the impactorIn this study, a line-nosed i

A New Approach toward Understanding Damage Mechanisms and Mechanics of Laminated Composites Due to Low-Velocity Impact: Part II—Analysis:

Impact behaviour of fibre-reinforced composites Recent developments in impact damage assessment of fibre composites Modelling impact of composite structures using small specimens Impact damage - tolerant composite structural design Damage resistance and tolerance of thick laminated woven roving GFRP plates subjected to low-velocity impact Elastic impact stress analysis of composite plates and cylinders Impact behaviour and analysis of CFRP laminated plates Perforation of FRP laminates and sandwich panels subjected to missile impact High velocity impact damage to polymer matrix composites

Hsi-Yung T. Wu

Papers

Transient dynamic analysis of laminated composite plates subjected to transverse impact