Abstract
While previous researchers have conducted their study on the relative impact performance of composite structures from a force or anenergy standpoint only, this proposed Composite Structure Impact Performance Assessment Program (CSIPAP) suggests a multi-parametermethodology to gain further insight in the impact behavior of composite structures. These are peak and critical force; critical anddissipated energy; contact duration and coefficient of restitution (COR), which is direct indication of effective structural stiffness; andresidual stiffness (normalized contact duration) which yields a plot that bears a striking resemblance with the normalized CompressionAfter Impact (CAI) strength. Using a determinate impactor/target system as baseline configuration, the program is applied toward theunderstanding of the role played in an impact event by fundamental impactor and target parameters. The equations previously derivedfor the prediction of the force–energy and residual stiffness curves are shown to apply to the configurations tested, thus confirming theirgeneral validity. A modification to the existing effective structural stiffness formulation, which does not account for impactor characteristics,is proposed, and it comprises the impactor material, size and mass characteristics._ 2005 Elsevier Ltd. All rights reserved.Keywords: B. Impact behavior; Damage resistance; C. Damage tolerance; C. Delamination
1. Introduction
1.1. Purpose of the research
An extensive literature review has indicated that manyquestions still surround the impact response of compositeplates. Particularly the ongoing debate on whether a forceor energy based criterion should be used to compareimpact test results on different configurations, and whetherforce or energy should be employed to uniquely and satisfactorilyassess the state of damage in the composite target.Interesting phenomena were observed in [1–3] in the attempt to address these issues, and a new methodologyis here suggested in order to fully benefit of all the informationavailable from an impact test.The present research has the double purpose of provingthe importance of characterizing the impact performanceof a composite target by means of multiple parameters,as suggested in this new Composite Structures Impact PerformanceAssessment Program (CSIPAP), as well as of verifyingits validity by applying it to specific parametricstudies in order to determine the influence of test configurationson the impact response of composite structures.The proposed CSIPAP is based on the simultaneous analysisof five plots, namely the Force, Energy, Coefficient ofRestitution (COR), Contact Duration and Residual Stiffnessplots, to fully and satisfactorily address the relativeimpact performance of composite targets.In order to build these plots, a specific test matrix has tobe employed. It is constituted of three consecutive impacttests, which are performed on each specimen and for eachstructural configuration.


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