| With the development of exploration of the space around the world,higher and higher requests are put on detecting equipment like space aircrafts and others.Space camera and detection telescope are both faced with the tendency of large aperture and lightweight.Carbon fiber reinforced polymer composite has a broad prospect in the field of reflective mirror manufacture because of its advanced physics property like low density,high stiffness and so on.The content of this paper are mainly focused on CFRP reflective mirror to obtain high surface precision,the ply alignment and influence factors of the surface aberration,via theoretical analysis,numerical simulation and experimental verification to offer some reference advices on how to design and produce high surface-precision CFRP reflective mirror.The contents of this paper are shown below.The corresponding theories about classical laminate theory and thermal expansion theory are commonly used in the CFRP reflective mirror design,including the construction method of total laminate's stiffness matrix and the characteristics of symmetric and balanced laminate,then the thermal constitutive equations and the relations between thermal stress and stiffness constitutive equations.After that this paper introduces several principles in the ply alignment design,and focuses on the influence of single ply angle,layup sequence,angle misalignment and room temperature to the precision of mirror surface.In the fourth chapter some researches about the rank of several representative ply alignments are calculated by normalized stiffness coefficients based on classical laminate theory and thermal expansion theory,and discusses the methods about how to obtain higher bending quasi-homogeneous laminate.This paper also focuses on the problem that how ply angle misalignment influences the precision of the surface,and analyzes the symmetric-balanced laminate under temperature variation,then takes single plies that are symmetric to the mid plane as research object,deduces relative formulas to prove that astigmatism of surface aberration are mainly caused by ply angle misalignment.In the production of CFRP mirror,ply angle misalignment is unavoidable,so this paper does finite calculation and simulation about that.This part of work are based on the finite calculation software COMSOL,constructs a model of reflective mirror with 70 mm aperture and 1.6mm thickness,and generates a series of normalized distributional random numbers as angles disturbance based on Monte Carlo method.In order to solve the rigid body displacement problem under thermal expansion of reflective mirror model,this paper constructes two body integration constraints in in-plane directions and Lagrangian multiplier displacement constraint on the bottom surface to take the place of force constraints.Then Zernike polynomials are utilized to do simulations of the results calculated by finite element method,and the equation set for the solution of Zernike coefficients are deduced based on least square method,then the contents above are realized by the coupled integration variables defined in COMSOL.After all the calculations,different kinds of aberrations are analyzed of simulation results,and layup sequences are sorted by the angle disturb resistance ability.Finally,many experimental verifications are done to prove the reasonability about the above theoretical research and finite element calculations.The first group of experiment includes two kinds of layup laminates,produced and detected with other factors controlled only to verify the correctness of ply angle misalignment leading to the astigmatism of reflective mirror.Then the next group of experiment is designed by containing many of the layup sequences used in the finite element calculation section,then the experimental results are compared with the simulation results. |
PDF Full Text Request