The problem of impact damage in laminated composite structures, and the consequent reduction in residual strength, has been a topic of continual research for over two decades. The number of journal papers on the subject now runs into four figures and most have been conscientiously reviewed by Abrate(1991, 1994, 1998). This review is not intended to be in the academic tradition, with emphasis on acknowledging the authorship of all the various research initiatives. Instead we present our opinions so that the reader can appreciate our current understanding of the problem, our capability of predicting by analysis, and the scope of the design tools for avoiding structural damage, or at least designing damage tolerant aerospace structures.

Impact on composite structures

Impact loading of plates and shells by free-flying projectiles: A review

Composite structures under ballistic impact

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

Impact behaviour of fibre-reinforced composite materials and structures

Ballistic impact behaviour of woven fabric composites: Formulation

Predicting the ballistic limit for plain woven glass/epoxy composite laminate

Simulation of a rigid plate hit by a cylindrical hemi-spherical tip-ended soft impactor

We are concerned with the ballistic impact response of three-dimensional two-step braided textile composites struck by a 36.1-g hemispherical tip-ended rigid cylindrical projectile. A series of quasistatic punch tests using a hemispherical indentor have been conducted to investigate the progressive damage modes of the target and to obtain the punch load-displacement relationship. In addition, a pneumatic launcher is used to propel the projectile with incident velocities ranging from 70 to 170 m/s. The ballistic limit is experimentally determined to be near 74.1 m/s. Commercially available finite element code (MARC) is incorporated with the constitutive relationship for three-dimensional two-step braided composites and the proposed static penetration model to simulate the dynamic impact response. An energy consideration is applied to predict the projectile's residual (or terminal) velocity. Numerical simulated result based on the static elastic properties of the target tends to overestimate the projectile terminal velocity. When the target's elastic moduli used in simulation are increased by 1.5 times the static values, good agreement is found between the simulated terminal velocities and test results for projectile incident velocities ranging from 70 to 180 m/s.

Ballistic impact response for two-step braided three-dimensional textile composites

This work is concerned with the dynamic impact response simulations of a soft model bird projectile striking a flat rigid panel. A hemi-spherical cylindrical tip-ended soft material was adopted to model a bird traveling with an incident velocity of 116, 197 and 253 m/s. The constitutive modeling of the soft impactor was studied. The diameter and the length of the impactor were 11.4 and 22.8 cm, respectively, and the weight of the impactor was 1.8 kg (i.e. 4 lb). Based on J. S. Wilbeck’s AFML-TR-77-134’s report, the material properties of the soft impactor was modeled to be similar to the properties of a real bird and the shear strength of the bird was neglected. The non-linear finite element code – LS-DYNA was used in this study to analyze the problem numerically. Three different formulation approaches, i.e. the Lagrangian (LAG), Eulerian (EUL) and the Arbitrary Lagrangian Eulerian (ALE) methods, were adopted in the present numerical analysis. Simulated dynamic pressure at the center of impact surface was computed based on three methods proposed. Simulated dynamic pressure versus time relationships were compared with Wilbeck’s test result and also checked against the stable stagnation pressure for the present study. Good results were found with the use of the coupled-field ALE method to obtain the dynamic pressure evolution after impact initiated and also the stable stagnation pressure. The results based on the LAG and EUL methods were reported to be less accurate.

S. T. Jenq

Papers

Predicting the ballistic limit for plain woven glass/epoxy composite laminate

Simulation of a rigid plate hit by a cylindrical hemi-spherical tip-ended soft impactor

Ballistic impact response for two-step braided three-dimensional textile composites

Simulation of a rigid plate hit by a cylindrical hemi-spherical tip-ended soft impactor

Ballistic Impact Response of 3-D Four-Step Braided Glass/Epoxy Composites