Mixed-mode fracture toughness tests were carried out on a multi-directional laminate making use of a Brazilian disk specimen. The composite laminate consisted of plain, balanced woven plies with tows in the $$0^{\circ }/90^{\circ }$$ 0 ∘ / 90 ∘ -directions and the $$+45^{\circ }/-45^{\circ }$$ + 45 ∘ / - 45 ∘ -directions. The delamination was placed between two of these plies by means of a polytetrafluoroethylene (PTFE) film. Tests at various loading angles were performed in order to obtain a wide range of mode mixities. Each ply was homogenized by means of a micro-mechanical model to obtain its effective properties. The specimens were analyzed by means of the finite element method. An interaction energy or M -integral was extended for this interface to obtain the stress intensity factors. The latter were used to determine the critical interface energy release rate and two phase angles. Employing this information, a three-dimensional failure criterion proposed elsewhere was presented. The criterion may be used to predict failure of a composite structure containing a delamination along the interface and material studied here.

中文翻译：

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多向编织层压板的混合模式测试

使用巴西圆盘试样在多向层压板上进行了混合模式断裂韧性测试。复合层压板由平的、平衡的编织层组成，在 $$0^{\circ }/90^{\circ }$$ 0 ∘ / 90 ∘ -方向和 $$+45^{\circ }/- 45^{\circ }$$ + 45 ∘ / - 45 ∘ -方向。分层通过聚四氟乙烯 (PTFE) 薄膜放置在其中两层之间。为了获得广泛的模式混合，在不同的加载角度下进行了测试。每层都通过微机械模型均质化以获得其有效性能。通过有限元方法对试样进行分析。为该界面扩展了相互作用能或 M 积分以获得应力强度因子。后者用于确定临界界面能量释放速率和两个相角。利用这些信息，提出了在别处提出的三维失效准则。该准则可用于预测复合结构的失效，该结构包含沿此处研究的界面和材料的分层。