A New Class of Thin Composite Parts for Small Batch Productions

Abstract

During the manufacturing process of polymeric composite materials, geometric unconformities may arise due to the onset of residual stresses, that are due to the chemical shrinkage of the matrix, to the polymerization process and to the difference in value between the CTE of matrix and that of fibres during cooling. The behaviour of thin non-planar form laminates (L, T, U shapes) is not the same of flat ones: even if the laminate presents a symmetrical and balanced structure, the condition of stresses and deformations is more complex and causes geometric deviations. The solution currently used to solve this problem is the equipment compensation. In this paper a new class of thin composite parts is presented. It consists of prepreg laminate stratified around an aluminium core, which serves as mould. In this way a new L-shape laminate may be developed for example. Experimental tests were carried out to produce the new class of composite parts. The obtained results demonstrated that the new class of thin composite parts is characterized by reduced geometrical unconformities. Moreover, it does not require an external forming mould, that is geometrically very complex, but an internal one, that is an aluminium core. The aluminium core is cheap, but it remains inside the part; therefore, the new class of parts is not adapt to large batch production. Finally, the new class presents a thermo-mechanical behaviour so simple that it is possible to foresee it numerically.