This invention relates to the composition and manufacturing process of a novel composite material with improved strength in the transverse direction. The proposed composite is able to better withstand peel loads that can cause early failure of typical composite materials by delamination, a phenomenon that occurs frequently when composite materials are joined by adhesive bonding and leads to lower overall joint strength. The proposed concept achieves higher transverse strength by improving the mechanical performance of the outer surfaces of the composite layup during the manufacturing process.
The use of composite materials has expanded greatly, for instance in the transportation sector, where their high specific strength and the stiffness they provide enables the manufacture of lightweight, high performance structures. However, bonded connections of composite materials are susceptible to failure by delamination due to the high peel loads that occur near the joints and the low transverse strength of the composites, needing the application of novel materials and techniques to reduce this issue.
Several techniques exist to improve the strength of composite materials, these typically require the insertion of transverse reinforcements such as Z-pins, which can negatively affect the elastic modulus, strength and fatigue performance of the materials. Other techniques such as 3D weaving and stitching require a complex manufacturing process, which greatly increases the cost of the final products.
Geometrical modifications to the substrates and adhesive layer can also achieve good effects but represent costly machining and shaping procedures that manufacturers tend to avoid.
The proposed technique retains the same type of composite layup but introduces a change in the matrix of the outer layer, attaining improved transverse behavior without noticeable performance loss in other key aspects.
The main problem solved by this invention is the inherent low strength to delamination of composite materials, especially when used as substrates in adhesive joints. When compared with other techniques used to improve transverse strength of composites, the proposed solution is simpler, requires no change to the fiber/weave structure and does not affect the key parameters of the finished composite such as the elastic modulus, strength and fatigue performance.
The materials created using this technique have wide uses in the transportation and defense sectors, especially for weight-critical impact resistant applications. For instance, this material can be used to manufacture fully-composite bonded crash absorbing structures for the automotive industry, both lighter and with better performance than those manufactured with metallic alloys.