JEC COMPOSITES MAGAZINE - Issue #37 - December 2007 - 56

KNOW-HOW Impact analysis Assessment of residual strength in impacted composite sandwich panels Simulation of impacted composite panels and calculation of residual strength after impact is a complex and challenging computational process. Accurate prediction requires the integration of material modelling capability with an explicit finiteelement dynamic solution, as well as damage tracking and fracture algorithms. A new computational methodology for assessing impact-related damage and determining residual strength after impact is discussed in this article. GALIB ABUMERI, TECHNICAL MANAGER ALPHASTAR P rediction of residual strength in composite panels after impact is challenged by the complexity of disciplines involved. Successful computation requires the integration of composite micro- and macro-mechanics with an explicit finite element solver, damage tracking, material degradation, and fracture. Assessing the behaviour of composites under impact loading is key to certification, especially as the demand for composites is increasing in automotive, aerospace and infrastructures. However, conventional industrial finite element codes have been challenged by the complex behaviour and variety of failure mechanisms in composite structures. In a typical finite element analysis, failure is assessed at the macroscale (lamina and/or laminate level). It is well known that the initiation of damage in composite materials occurs at the microscale (fibre/matrix level) and not as commonly practiced by commercial finite element analysis software, which generally results in conservative design. There is a need for a coupled solution that evaluates material damage at the lowest scale, consistent with the physical behaviour of the material. This becomes more important in high-velocity or time-dependent impact problems. Such a methodology is developed and now integrated in a software system named GENOA [1] and in the Mythology it should be perform durability [2] and doamage tolerance. In this paper, the coupled explicit finite element and durability analysis capability is used to evaluate the performance of a composite panel under impact loading. Figure 1 shows the panel with composite face-sheet and centre core joined by an adhesive layer. The strength in the panel under compression load (with and without impact) is quantified. Fig. 1: Impact on sandwich composite panel Methodology The novel methodology relies on progressive failure analysis to perform durability [2] and damage tolerance assessment of composite materials and structures (Figure 2): Fig. 2: Computational approach for durability evaluation of impacted composite structures 1) finite element thermal and structural analysis, 2) composite mechanics and fracture mechanics options, 3) damage progression tracking, 4) probabilistic risk assessment, 5) minimum damage design optimization, and 6) material characterization codes to scale up the effects of local damage mechanisms to the structure level to evaluate overall performance and integrity. JEC Composites Magazine / No37 December 2007

JEC COMPOSITES MAGAZINE - Issue #37 - December 2007

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